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  • 1.
    Ajalloueian, Fatemeh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Tavanai, Hossein
    Hilborn, Jons
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Donzel-Gargand, Olivier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wickham, Abeni
    Arpanaei, Ayyoob
    Emulsion Electrospinning as an Approach to Fabricate PLGA/Chitosan Nanofibers for Biomedical Applications2014In: BioMed Research International, ISSN 2314-6133, Vol. 2014, p. 475280-Article in journal (Refereed)
    Abstract [en]

    Novel nanofibers from blends of polylactic-co-glycolic acid (PLGA) and chitosan have been produced through an emulsion electrospinning process. The spinning solution employed polyvinyl alcohol (PVA) as the emulsifier. PVA was extracted from the electrospun nanofibers, resulting in a final scaffold consisting of a blend of PLGA and chitosan. The fraction of chitosan in the final electrospun mat was adjusted from 0 to 33%. Analyses by scanning and transmission electron microscopy show uniform nanofibers with homogenous distribution of PLGA and chitosan in their cross section. Infrared spectroscopy verifies that electrospun mats contain both PLGA and chitosan. Moreover, contact angle measurements show that the electrospun PLGA/chitosanmats are more hydrophilic than electrospun mats of pure PLGA. Tensile strengths of 4.94 MPa and 4.21 MPa for PLGA/chitosan in dry and wet conditions, respectively, illustrate that the polyblend mats of PLGA/chitosan are strong enough for many biomedical applications. Cell culture studies suggest that PLGA/chitosan nanofibers promote fibroblast attachment and proliferation compared to PLGA membranes. It can be assumed that the nanofibrous composite scaffold of PLGA/chitosan could be potentially used for skin tissue reconstruction.

  • 2.
    Akhtar, Sultan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    TEM investigations of attachment of functionalized magnetic nanoparticles to DNA-coils acting as a biosensor2010In: Scandem 2010, Stockholm, Sweden, June 8-11, 2010Conference paper (Refereed)
  • 3.
    Akhtar, Sultan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Yang, W.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Visualization of functionalization of nano-particles and graphene in the TEM2010In: Advanced Materials Workshop 2010, 2010Conference paper (Refereed)
    Abstract [en]

    Recently, the activity on functionalized nano-objects has strongly increased. Yet, there are, to our knowledge no techniques available that visualize the attachment of molecules to nano-entities such as nanoparticles and graphene. In this work, we show a methodology to analyse the attachment of molecules to nanoparticles and graphene. The difficulty of such transmission electron microscopy (TEM) characterization consists in the high beam sensitivity of these nanoobjects. We employed a high resolution- as well as diffraction contrast-imaging methods to characterize graphene. First, we have developed a method to measure the thickness of free-standing graphene-like layers. The refinement of these imaging techniques enabled the imaging of functionalized C60 (fullerene) on top of a few-layer graphene flake by TEM. We also developed a methodology to visualize the attachment of functionalized gold and magnetic nanoparticles (different sizes) to nonstained and unlabeled single strand DNA-coils. This technique can be used to understand the interaction of a large variety of functionalized nanoparticles with their solution environment and/or macromolecular structures for their large applications.

  • 4.
    Akhtar, Sultan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Zardán Gómez de la Torre, Teresa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Russell, Camilla
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Real-Space Transmission Electron Microscopy Investigations of Attachment of Functionalized Magnetic Nanoparticles to DNA-Coils Acting as a Biosensor2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 41, p. 13255-13262Article in journal (Refereed)
    Abstract [en]

    The present work provides the first real-space analysis of nanobead-DNA coil interactions. Immobilization of oligonucleotide-functionalized magnetic nanobeads in rolling circle amplified DNA-coils was studied by complex magnetization measurements and transmission electron microscopy (TEM), and a statistical analysis of the number of beads hybridized to the DNA-coils was performed. The average number of beads per DNAcoil using the results from both methods was found to be around 6 and slightly above 2 for samples with 40 and 130 nm beads, respectively. The TEM analysis supported an earlier hypothesis that 40 nm beads are preferably immobilized in the interior of DNA-coils whereas 130 nm beads, to a larger extent, are immobilized closer to the exterior of the coils. The methodology demonstrated in the present work should open up new possibilities for characterization of interactions of a large variety of functionalized nanoparticles with macromolecules, useful for gaining more fundamental understanding of such interactions as well as for optimizing a number of biosensor applications.

  • 5.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Eriksson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Li, Hu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, S. Hassan M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar, M. S. Sharath
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    An electron energy loss spectrometer based streak camera for time resolved TEM measurements2017In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 176, p. 5-10Article in journal (Refereed)
    Abstract [en]

    We propose an experimental setup based on a streak camera approach inside an energy filter to measure time resolved properties of materials in the transmission electron microscope (TEM). In order to put in place the streak camera, a beam sweeper was built inside an energy filter. After exciting the TEM sample, the beam is swept across the CCD camera of the filter. We describe different parts of the setup at the example of a magnetic measurement. This setup is capable to acquire time resolved diffraction patterns, electron energy loss spectra (EELS) and images with total streaking times in the range between 100 ns and 10 μs.

  • 6.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Warnatz, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Xie, Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS2019In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 196, p. 192-196Article in journal (Refereed)
    Abstract [en]

    The weak signal strength in electron magnetic circular dichroism (EMCD) measurements remains one of the main challenges in the quantification of EMCD related EELS spectra. As a consequence, small variations in peak intensity caused by changes of background intervals, choice of method for extraction of signal intensity and equally differences in sample quality can cause strong changes in the EMCD signal. When aiming for high resolution quantitative EMCD, an additional difficulty consists in the fact that the two angular resolved EELS spectra needed to obtain the EMCD signal are taken at two different instances and it cannot be guaranteed that the acquisition conditions for these two spectra are identical.  Here, we present an experimental setup where we use a double hole aperture in the transmission electron microscope to obtain the EMCD signal in a single acquisition. This geometry allows for the parallel acquisition of the two electron energy loss spectra (EELS) under exactly the same conditions. We also compare the double aperture acquisition mode with the qE acquisition mode which has been previously used for parallel acquisition of EMCD. We show that the double aperture mode not only offers better signal to noise ratio as compared to qE mode but also allows for much higher acquisition times to significantly improve the signal quality which is crucial for quantitative analysis of the magnetic moments.

    The full text will be freely available from 2020-10-20 18:43
  • 7.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Warnatz, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Xie, Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Towards Quantitative Nanomagnetism in Transmission Electron Microscope by the Use of Patterned Apertures2019In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 25, no S2, p. 654-655Article in journal (Other academic)
    The full text will be freely available from 2020-02-05 12:40
  • 8.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xie, Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    van Sebille, Martijn
    Delft University of Technology, Netherlands.
    Fusi, Adele
    Delft University of Technology, Netherlands.
    van Swaaij, Rene A C M M
    Delft University of Technology, Netherlands.
    Zeman, Miro
    Delft University of Technology, Netherlands.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    TEM analysis of multilayered nanostructures formed in the rapid thermal annealed silicon rich silicon oxide film2016In: European Microscopy Congress 2016: Proceedings, 2016, p. 965-966Conference paper (Other academic)
    Abstract [en]

    Silicon (Si) nanoparticles (NPs) embedded in an ultrathin silicon rich silicon oxide (SRSO) film through the thermal annealing process has emerged as a highly absorbing layer for third-generation solar cells 1. The concept of using Si NPs is to achieve a band gap tunable absorber layer by controlling the size and structure of Si NPs because of the quantum confinement effect 2. In our study, a multilayer stack of silicon oxide with 35 periods of alternating layers of 1-nm thick near-stoichiometric and 3-nm thick Si-rich hydrogenated silicon oxide were deposited on fused quartz substrate by plasma-enhanced chemical vapor deposition (PECVD) method. Two samples were annealed using a rapid thermal annealing (RTA) furnace in forming gas atmosphere (90% N2 + 10% H2) for 210s and 270s respectively. From the Raman spectroscopy, a reduction in crystallinity of Si has been discovered from 210s annealed sample to 270s annealed sample (shown in Figure 2). The goal of transmission electron microscopy (TEM) analysis is to investigate the nanostructural change of Si in these two annealed samples and try to correlate the TEM observations to the Raman spectroscopy results.

    As the dimension of the Si nanostructures formed in SRSO films is in nanometer-scale, the energy-filtered TEM (EFTEM) tomography technique using the low-loss signals in electron energy-loss spectroscopy (EELS) has been applied as a powerful technique to correlate the precipitated Si nanostructures to the phase transformation mechanisms in the thermally annealed SRSO films 3. In this case, EFTEM spectrum-imaging (SI) technique was applied to characterize the Si nanostructures formed in SRSO films by different annealing times. The EFTEM SI dataset was acquired from -4eV to 40eV using a 2eV energy slit and the reconstructed zero loss peak (ZLP) was used to calibrate the spectra shift. Si plasmon images were extracted by fitting a Gaussian into the low-loss region with a peak position at 16.7 eV 4 and FWHM of 4.5 eV. In order to analyze the multilayer structures at different annealing durations, the TEM samples were prepared in cross sectional geometry using the conventional polishing and ion milling methods.

    Figure 1 shows the EFTEM images extracted from the Si plasmon peak, in these images Si appears as bright contrasts. For shorter annealing time, an alternating bright and dark contrast can be observed which indicates that the multilayer structure still remains whereas for longer annealing time, Si shows nanoparticles like contrast. The continuous layer like contrasts shown in Figure 1(a) indicates the overlapping of the contrasts generated by small Si crystallites in a very high density. After longer annealing time (Figure 1(b)), the small Si crystallites grow in size but may take overall less volume fraction due to the Ostwald ripening process. Therefore, it explains the reduction in crystallinity of Si discovered from 210s annealed sample to 270s annealed sample by Raman. However, such a reduction in Si crystallinity was not observed in nitrogen annealed SRSO films, this indicates that samples annealed in the forming gas environment follow a different crystallization mechanism and hydrogen must play a decisive role during the Si crystallization at the initial stage.

  • 9.
    Barbe, Jeremy
    et al.
    CEA, Liten, Grenoble, och Université de Toulouse, UPS, INPT, LAPLACE, Frankrike.
    Xie, Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Faucherand, Pascal
    CEA, Liten, Grenoble, Frankrike.
    Morin, Christine
    CEA, Liten, Grenoble Frankrike.
    Rapisarda, Dario
    CEA, Liten, Grenoble, Frankrike.
    De Vito, Eric
    CEA, Liten, Grenoble, Frankrike.
    Makasheva, Kremena
    Université de Toulouse, UPS, INPT, LAPLACE, Frankrike.
    Despax, Bernard
    Université de Toulouse, UPS, INPT, LAPLACE, Frankrike.
    Perraud, Simon
    CEA, Liten, Grenoble, Frankrike.
    Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth2012In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 522, p. 136-144Article in journal (Refereed)
    Abstract [en]

    The present study demonstrates the growth of silicon nanocrystals on amorphous silicon carbide alloy thin films. Amorphous silicon carbide films [a-Si1 − xCx:H (with x < 0.3)] were obtained by plasma enhanced chemical vapor deposition from a mixture of silane and methane diluted in hydrogen. The effect of varying the precursor gas-flow ratio on the film properties was investigated. In particular, a wide optical band gap (2.3 eV) was reached by using a high methane-to-silane flow ratio during the deposition of the a-Si1 − xCx:H layer. The effect of short-time annealing at 700 °C on the composition and properties of the layer was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was observed that the silicon-to-carbon ratio in the layer remains unchanged after short-time annealing, but the reorganization of the film due to a large dehydrogenation leads to a higher density of SiC bonds. Moreover, the film remains amorphous after the performed short-time annealing. In a second part, it was shown that a high density (1 × 1012 cm− 2) of silicon nanocrystals can be grown by low pressure chemical vapor deposition on a-Si0.8C0.2 surfaces at 700 °C, from silane diluted in hydrogen. The influence of growth time and silane partial pressure on nanocrystals size and density was studied. It was also found that amorphous silicon carbide surfaces enhance silicon nanocrystal nucleation with respect to SiO2, due to the differences in surface chemical properties.

  • 10.
    Bhattacharya, Kunal
    et al.
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    El-Sayed, Ramy
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Andon, Fernando T.
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Mukherjee, Sourav P.
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Gregory, Joshua
    Karolinska Inst, Ctr Allergy Res, S-17177 Stockholm, Sweden;Karolinska Inst, Inst Environm Med, Div Physiol, S-17177 Stockholm, Sweden.
    Li, Hu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Zhao, Yinchen
    Royal Inst Technol, Dept Mat & Nanophys, Funct Mat Div, S-16440 Stockholm, Sweden.
    Seo, Wanji
    Univ Pittsburgh, Dept Chem, Pittsburgh, PA 15260 USA.
    Fornara, Andrea
    SP Tech Res Inst Sweden, Unit Chem Mat & Surfaces, S-11486 Stockholm, Sweden.
    Brandner, Birgit
    SP Tech Res Inst Sweden, Unit Chem Mat & Surfaces, S-11486 Stockholm, Sweden.
    Toprak, Muhammet S.
    Royal Inst Technol, Dept Mat & Nanophys, Funct Mat Div, S-16440 Stockholm, Sweden.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Star, Alexander
    Univ Pittsburgh, Dept Chem, Pittsburgh, PA 15260 USA.
    Fadeel, Bengt
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Lactoperoxidase-mediated degradation of single-walled carbon nanotubes in the presence of pulmonary surfactant2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 91, p. 506-517Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) may elicit inflammatory responses following pulmonary exposure. Conversely, enzymatic biodegradation of CNTs by inflammatory cells has also been reported. The aim of this study was to study the degradation of oxidized single-walled CNTs (ox-SWCNTs) by lactoperoxidase (LPO), a secreted peroxidase present in the airways, and whether pulmonary surfactant affects this biodegradation. To this end, ox-SWCNTs were incubated in vitro with recombinant bovine LPO + H2O2 + NaSCN in the presence and absence of porcine lung surfactant (Curosurf (R)) and biodegradation was monitored using UV-Vis-NIR spectroscopy, Raman spectroscopy, and scanning electron microscopy. The interaction of recombinant LPO with bundles of ox-SWCNTs was confirmed by atomic force microscopy. Cell-free biodegradation of ox-SWCNTs was also observed ex vivo in murine bronchoalveolar lavage fluid in the presence of H2O2 + NaSCN. Our study provides evidence for biodegradation of ox-SWCNTs with a lung surfactant 'bio-corona' and expands the repertoire of mammalian percuddases capable of biodegradation of ox-SWCNTs. These findings are relevant to inhalation exposure to these materials, as LPO serves as an important component of the airway defense system.

  • 11.
    Bjurström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lidbaum, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Wingqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Synthesis of highly textured thin piezoelectric AlN films with a tilted c-axis2007Conference paper (Refereed)
  • 12.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Surpi, Alexandro
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Östlund, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Michler, J.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nanocontact Fabrication and Characterization2007Conference paper (Refereed)
  • 13.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Di Cristo, Valentina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Conduction properties of graphene as a function of ion irradiation and acid treatment2011In: Graphene 2011 - 11th to 14th April 2011. Bilbao, Spain., 2011Conference paper (Refereed)
  • 14.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Akhtar, Sultan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Cavalca, Filippo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Di Cristo, Valentina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Exfoliation, transfer and electrical characterization of graphene2010In: Indian-Swedish Conference on Functional Materials, Uppsala, Sweden; 28-30 June 2010, 2010Conference paper (Refereed)
  • 15.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Coronel, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Grigeriev, A.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Dielectrophoretic trapping of gold nanoparticles on SAM-prepared nanogaps: A comparative study of different molecular systems2009In: presentation European Conference on Molecular Electronics (ECME2009), Copenhagen, Denmark (Sept 2009), 2009Conference paper (Other academic)
  • 16.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Dielectrophoretic trapping of gold nanoparticles on SAM-prepared nanogaps: A comparative study of different molecular systems2010In: International Conference on Molecular Electronics, Emmetten, Switzerland (Jan 2010), 2010Conference paper (Refereed)
  • 17.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Electrophoretic trapping of gold nanoparticles on sam-prepared nanogaps: A comparative study of different molecular systems2009Conference paper (Refereed)
  • 18.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Leifer, Klaus
    Fabrication and characterization of high resistance nanogaps used for studies of different molecular electronics systems2009Conference paper (Refereed)
  • 19.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Quinlan, R A
    Holloway, B C
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    An In-Situ Prepared Nano-Manipulator Tip for Electrical Characterization of Free Standing Graphene Like Sheets Inside a Focused Ion Beam/Scanning Electron Microscope2011In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 6, no 2, p. 162-168Article in journal (Refereed)
    Abstract [en]

    Although contacting and moving atoms has been demonstrated using probe techniques, for many nano-objects, a fast and reproducible nano-probe technique is needed to acquire a large number of electrical measurements on nano-objects that are often similar but not the identical. Nano-manipulators have become a common tool in many scanning electron microscopes (SEM) and focussed ion beam devices (FIB). They can be rapidly and reproducibly moved from one nano-object to another. In this work we present a procedure to obtain reproducible electrical measurements of nano- to micron-sized objects by using a sharp, tungsten tip with well defined surface properties. The tip is a part of a manipulator and is sharpened in-situ by using the gallium ion beam inside a focused ion beam/scanning electron microscope (FIB/SEM). The contact resistance between a Au surface and the tip is 70 kΩ before the sharpening procedure and 10 Ω after sharpening. The leakage current of the total set-up of 10pA makes it possible to measure currents through a variety of nano-objects. This measurement technique is applied to measure the resistance of as grown, water treated and two HCl treated carbon nanosheets (CNS). These CNS vary in size and morphology. Using this nano-contacting set-up, we could obtain measurements of more than 400 different CNS. The obtained histograms allow us to observe a clear decrease of the resistance between original and 3 hour acid treated CNSs. We observe that longer periods of exposure of the CNS to the HCl do not further modify the resistance.

  • 20.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, S. Hassan. M.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Leifer, Klaus
    Fabrication and use of high resistance nanogaps for application in molecular electronics2009Conference paper (Refereed)
  • 21.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fabrication and characterization of highly reproducible, high resistance nanogaps made by focused ion beam milling2007Conference paper (Refereed)
  • 22.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Fabrication and characterization of highly reproducible, high resistance nanogaps made by focused ion beam milling2008Conference paper (Refereed)
  • 23.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fabrication and characterization of highly reproducible, high resistance nanogaps made by focused ion beam milling2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 28, p. 285301-Article in journal (Refereed)
    Abstract [en]

    Nanoelectrodes were fabricated combining photolithography, electron beam lithography and focused ion beam milling allowing for large scale integration and nanoengineering of the electrode properties. The structure determination by transmission and scanning electron microscopy showed a highly reproducible gap width. The atomic scale electrode structure was characterized using scanning and transmission electron microscopy. The nanogap resistances were found to be the highest hitherto reported for nanogaps, namely in the 300–1300 TΩ range. Gold nanoparticles were trapped by ac dielectrophoresis, and the electrodes were shown to be stable enough to endure empty gap voltages as high as 5 V as well as currents high enough to induce fusing of trapped nanoparticles.

  • 24. Borges, J.
    et al.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kumar, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rodrigues, M. S.
    Duarte, N.
    Martins, B.
    Dias, J. P.
    Cavaleiro, A.
    Vaz, F.
    Microstructural evolution of Au/TiO2 nanocomposite films: The influence of Au concentration and thermal annealing2015In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 580, p. 77-88Article in journal (Refereed)
    Abstract [en]

    Nanocomposite thin films consisting of a dielectric matrix, such as titanium oxide (TiO2), with embedded gold (Au) nanoparticles were prepared and will be analysed and discussed in detail in the present work. The evolution of morphological and structural features was studied for a wide range of Au concentrations and for annealing treatments in air, for temperatures ranging from 200 to 800 degrees C. Major findings revealed that for low Au atomic concentrations (at.%), there are only traces of clustering, and just for relatively high annealing temperatures, T >= 500 degrees C. Furthermore, the number of Au nanoparticles is extremely low, even for the highest annealing temperature, T = 800 degrees C. It is noteworthy that the TiO2 matrix also crystallizes in the anatase phase for annealing temperatures above 300 degrees C. For intermediate Au contents (5 at.% <= C-Au <= 15 at.%), the formation of gold nanoclusters was much more evident, beginning at lower annealing temperatures (T >= 200 degrees C) with sizes ranging from 2 to 25 nm as the temperature increased. A change in the matrix crystallization from anatase to rutile was also observed in this intermediate range of compositions. For the highest Au concentrations (>20 at.%), the films tended to form relatively larger clusters, with sizes above 20 nm (for T >= 400 degrees C). It is demonstrated that the structural and morphological characteristics of the films are strongly affected by the annealing temperature, as well as by the particular amounts, size and distribution of the Au nanoparticles dispersed in the TiO2 matrix.

  • 25.
    Borges, J.
    et al.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;Czech Tech Univ, Fac Elect Engn, Dept Control Engn, Tech 2, Prague 6, Czech Republic.;Inst Pedro Nunes, Lab Ensaios Desgaste & Mat, Rua Pedro Nunes, P-3030199 Coimbra, Portugal.;Univ Coimbra, SEG CEMUC, Mech Engn Dept, P-3030788 Coimbra, Portugal..
    Pereira, R. M. S.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;Univ Minho, Ctr Matemat, Campus Gualtar, P-4710057 Braga, Portugal.;Univ Minho, Dept Matemat & Aplicacoes, Campus Gualtar, P-4710057 Braga, Portugal..
    Rodrigues, M. S.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;Inst Pedro Nunes, Lab Ensaios Desgaste & Mat, Rua Pedro Nunes, P-3030199 Coimbra, Portugal..
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kumar, Saroj
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Cavaleiro, A.
    Univ Coimbra, SEG CEMUC, Mech Engn Dept, P-3030788 Coimbra, Portugal..
    Polcar, T.
    Czech Tech Univ, Fac Elect Engn, Dept Control Engn, Tech 2, Prague 6, Czech Republic.;Univ Southampton, Natl Ctr Adv Tribol Southampton nCATS, Southampton SO17 1BJ, Hants, England..
    Vasilevskiy, M. I.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;City Univ Hong Kong, Dept Phys & Mat Sci, Hong Kong, Hong Kong, Peoples R China.;City Univ Hong Kong, CFP, Hong Kong, Hong Kong, Peoples R China..
    Vaz, F.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal..
    Broadband Optical Absorption Caused by the Plasmonic Response of Coalesced Au Nanoparticles Embedded in a TiO2 Matrix2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 30, p. 16931-16945Article in journal (Refereed)
    Abstract [en]

    The effect of Au nanopattides' (NPs) concentration, site, and spatial distribution within a TiO2 dielectric matrix on the localized surface plasmon resonance (LSPR) band characteristics was experimentally and theoretically studied. The results of the analysis of the Au NPs' size distributions allowed us to conclude that isolated NPs grow only up to 5 to 6 nm in site, even for the highest annealing temperature used. However, for higher volume fractions of Au, the coalescence of closely located NPs yields elongated clusters that are much larger in size and cause a considerable broadening of the LSPR band. This effect was confirmed by Monte Carlo modeling results. Coupled dipole equations were solved to find the electromagnetic modes of a supercell, where isolated and coalesced NPs were distributed, from which an effective dielectric function of the nanocomposite material was calculated and used to evaluate the optical transmittance and reflectance spectra. The modeling results suggested that the observed LSPR band broadening is due to a wider spectral distribution of plasmonic modes, caused by the presence of coalesced NPs (in addition to the usual damping effect). This is particularly important for detection applications via surface-enhanced Raman spectroscopy (SERS), where it is desirable to have a spectrally broad LSPR band in order:to favor the fulfillment of the conditions of resonance matching, to electronic transitions in detected species.

  • 26.
    Borges, J.
    et al.
    Czech Tech Univ, Fac Elect Engn, Dept Control Engn, Tech 2, CR-16635 Prague 6, Czech Republic..
    Rodrigues, M. S.
    Univ Minho, Ctr Fis, P-4710057 Braga, Portugal.;Inst Pedro Nunes, Lab Ensaios Desgaste & Mat, P-3030199 Coimbra, Portugal..
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kumar, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Evaristo, M.
    Univ Coimbra, Dept Mech Engn, SEG CEMUC, P-3030788 Coimbra, Portugal..
    Cavaleiro, A.
    Univ Coimbra, Dept Mech Engn, SEG CEMUC, P-3030788 Coimbra, Portugal..
    Apreutesei, M.
    INSA Lyon, MATEIS Lab, F-69621 Villeurbanne, France..
    Pereira, R. M. S.
    Univ Minho, Ctr Fis, P-4710057 Braga, Portugal.;Univ Minho, Ctr Matemat, Braga, Portugal..
    Vasilevskiy, M. I.
    Univ Minho, Ctr Fis, P-4710057 Braga, Portugal..
    Polcar, T.
    Czech Tech Univ, Fac Elect Engn, Dept Control Engn, Tech 2, CR-16635 Prague 6, Czech Republic.;Univ Southampton, Natl Ctr Adv Tribol Southampton nCATS, Southampton SO17 1BJ, Hants, England..
    Vaz, F.
    Univ Minho, Ctr Fis, P-4710057 Braga, Portugal..
    Thin films composed of gold nanoparticles dispersed in a dielectric matrix: The influence of the host matrix on the optical and mechanical responses2015In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 596, p. 8-17Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticles were dispersed in two different dielectric matrices, TiO2 and Al2O3, using magnetron sputtering and a post-deposition annealing treatment. The main goal of the present work was to study how the two different host dielectric matrices, and the resulting microstructure evolution (including both the nanoparticles and the host matrix itself) promoted by thermal annealing, influenced the physical properties of the films. In particular, the structure and morphology of the nanocomposites were correlated with the optical response of the thin films, namely their localized surface plasmon resonance (LSPR) characteristics. Furthermore, and in order to scan the future application of the two thin film system in different types of sensors (namely biological ones), their functional behaviour (hardness and Young's modulus change) was also evaluated. Despite the similar Au concentrations in both matrices (similar to 11 at.%), very different microstructural features were observed, which were found to depend strongly on the annealing temperature. The main structural differences included: (i) the early crystallization of the TiO2 host matrix, while the Al2O3 one remained amorphous up to 800 degrees C; (ii) different grain size evolution behaviours with the annealing temperature, namely an almost linear increase for the Au:TiO2 system (from 3 to 11 nm), and the approximately constant values observed in the Au:Al2O3 system (4-5 nm). The results from the nanoparticle size distributions were also found to be quite sensitive to the surrounding matrix, suggesting different mechanisms for the nanoparticle growth (particle migration and coalescence dominating in TiO2 and Ostwald ripening in Al2O3). These different clustering behaviours induced different transmittance-LSPR responses and a good mechanical stability, which opens the possibility for future use of these nanocomposite thin film systems in some envisaged applications (e.g. LSPR-biosensors).

  • 27.
    Bručas, Rimantas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Chalmers tekniska högskola.
    Hanson, M.
    Chalmers tekniska högskola.
    Gunnarsson, R.
    Chalmers tekniska högskola.
    Wahlström, E.
    van Kampen, Maarten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Lidbaum, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Magnetic and transport properties of Ni81Fe19/Al2O3 granular multilayers approaching the superparamagnetic limit2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 7, p. 073907-Article in journal (Refereed)
    Abstract [en]

    The magnetic and transport properties of Ni81Fe 19/Al2O3 granular multilayer films were studied in relation to their structural properties as the nominal thickness t of the permalloy (Ni81Fe19) layer was varied near the percolation limit: in the range of 8≤t≤ 16 Å while keeping the nominal thickness of the Al2O3 layers constant at 16 Å. A good structural quality of the multilayers was demonstrated by low angle x-ray reflectivity measurements, and transmission electron microscopy showed the transition from continuous permalloy layers separated by aluminium oxide layers for t= 16 Å to metal grains dispersed in the insulator at t=8 Å. Magnetization measurements showed the gradual transition from ferromagnetic layers to superparamagnetic clusters and grains that successively become blocked as the temperature decreases. A strong correlation between transport and structural properties was observed in the temperature (T) dependence of the electrical resistance measured with the current in the plane in the range of 2 ≤T≤300 K: a gradual change of behavior from continuous permalloy layers with conducting interlayer connections for t=16 Å. to isolated permalloy grains in a dielectric for the film with t= 10 Å. The percolation occurs between 12 and 10 Å, as deduced both from the magnetic and resistive properties. The discontinuous metal films were analyzed within models for thermally assisted tunneling, yielding estimates of the tunneling barrier for intralayer conduction of about 20 meV for t= 10 Å. A significant magnetic field dependence of the resistance increasing with decreasing temperature was observed in all samples.

  • 28.
    Cai, Yixiao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Li, Hu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Biomineralization on Single Crystalline Rutile: The Modulated Growth of Hydroxyapatite by Fibronectin in a Simulated Body Fluid2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, p. 35507-35516Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to probe the complex interaction between surface bioactivity and protein adsorption on single crystalline rutile. Our previous studies have shown that single crystalline rutile possessed in vitro bioactivity and the crystalline faces affected the hydroxyapatite (HA) formation. However, upon implantation, a fast adsorption of proteins, from the biological fluids, is intermediated by a water layer towards the biomaterial interface. Thus the effect of protein on the bioactivity must be addressed. In this study, the HA growth dynamics on (001), (100) and (110) faces was investigated in a simulated body fluid with the presence of fibronectin (FN) by two different processes. The surface adhesion of each face before and after FN adsorption, as revealed by direct numerical values, was determined by atomic force microscopy (AFM) based peak force quantitative nanomechanical mapping (PF-QNM) for the first time. The findings suggest the surface energies of FN pre-adsorbed (001), (100) and (110) faces have been enhanced, leading to the subsequent accelerated HA formation. Furthermore, (001) and (100) faces were found to have larger coverage of HA crystals than (110) face at an early stage. In addition, various characterizations were performed to probe the chemical and crystal structures of as-grown biomimetic HA crystals, and in particular, the Ca/P ratio variations at different soaking time points.

  • 29.
    Calard, Francois
    et al.
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt , Architectures Mol & Mat Nanostruct, Montpellier, France..
    Wani, Ishtiaq Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hayat, Aqib
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jarrosson, Thibaut
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt Montpellier, Architectures Mol & Mat Nanostruct, Montpellier, France..
    Lere-Porte, Jean-Pierre
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt Montpellier, Architectures Mol & Mat Nanostruct, Montpellier, France..
    Jafri, S. Hassan M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Mirpur Univ Sci & Technol, Dept Elect Engn, Azad Kashmir, Pakistan..
    Serein-Spirau, Francoise
    Ecole Natl Super Chim Montpellier, Inst Charles Gerhardt Montpellier, Architectures Mol & Mat Nanostruct, UMR CNRS 5253, Montpellier, France..
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Designing sterically demanding thiolate coated AuNPs for electrical characterization of BPDT in a NP-molecule-nanoelectrode platform2017In: MOLECULAR SYSTEMS DESIGN & ENGINEERING, ISSN 2058-9689, Vol. 2, no 2, p. 133-139Article in journal (Refereed)
    Abstract [en]

    Molecular electronics with single or few molecules requires a stable metal-molecule nanojunction platform. Herein, we report the design and synthesis of gold nanoparticles coated with sterically demanding thiol ligands that are essential to fabricate a versatile and stable nanoelectrode-molecule-nanoparticle platform suitable for electrical characterization of small organic molecules. By combining.-tetraphenylmethane ether functionalized alkyl thioacetate and alkyl thiols, we prepared highly stable gold nanoparticles in a one-phase reaction providing simple and efficient purification. This robust preparation gives highly pure nanoparticles in very high yields (up to 90%) with long-time shelf stability. The synthesis in this work has superior reproducibility compared to previous synthesis processes that are currently being used for such molecular electronics platforms. Electron microscopy confirms the formation of uniform and small nanoparticles in the range of 5 to 7 nm. These nanoparticles with different ligand surface coverages were placed in a 20 nm nanoelectrode setup using dielectrophoretic forces. This setup was utilized to characterize the conductivity of the molecular wire 4,4'-biphenyldithiol introduced via ligand placeexchange under ambient conditions.

  • 30.
    Cavalca, Filippo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Jafri, S.H.M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Akhtar, Sultan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    DIY graphene production, transfer and characterization2009In: First Nordic Workshop on graphene science in 20-21 April, 2009, Uppsala., 2009Conference paper (Other academic)
  • 31.
    Chulapakorn, Thawatchart
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sychugov, Ilya
    Royal Institute of Technology (KTH), Department of Materials and Nano Physics, SE-164 40 Kista, Sweden.
    Suvanam, Sethu Saveda
    Royal Institute of Technology (KTH), School of Information and Communication Technology, PO Box Electrum 229, SE-16440 Kista, Sweden.
    Xie, Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    LEIFER, KLAUS
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Linnros, Jan
    Royal Institute of Technology (KTH), Department of Materials and Nano Physics, SE-164 40 Kista, Sweden.
    Hallén, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Royal Institute of Technology, School of Information & Communication Technology, SE-16440 Kista, Sweden.
    Ion Beam Synthesis of Luminescent Silicon NanoparticlesManuscript (preprint) (Other academic)
  • 32.
    Coronel, Ernesto
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Elektronmikroskopi och Nanoteknologi.
    Hanson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materialvetenskap.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Elektronmikroskopi och Nanoteknologi.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materialvetenskap.
    Mechanisms of Work Material Adhesion in Tooling Operations Revealed by TEM2006Conference paper (Other academic)
  • 33.
    Coronel, Ernesto
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Microstructural characterization of Zn1-XMgXO buffers layer in CIGS solar cells2007Conference paper (Other academic)
  • 34.
    Correa Filho, Luimar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Schmidt, Susann
    Linköping University.
    Högberg, Hans
    Linköping University.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear resistance of silicon nitride coatings in a hard-on-hard contact2016Conference paper (Refereed)
  • 35.
    DONZEL-GARGAND, O.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    THERSLEFF, T.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    FOURDRINIER, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    LEIFER, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    CIGS on steel substrate: Diffusion of iron through the barrier layer2013In: GradSAM Workshop, 2013, Uppsala: GradSAM , 2013Conference paper (Other (popular science, discussion, etc.))
  • 36.
    Donzel-Gargand, O.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Thersleff, T.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fourdrinier, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    TEM analyses of diffusion barrier on steel substrate2013In: MyFAB Workshop, Uppsala: MyFAB , 2013Conference paper (Other academic)
  • 37.
    Donzel-Gargand, Olivier
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fourdrinier, Lionel
    CRM group, Liège (Belgium).
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Functionalization of steel substrate: influence of barrier nature on element diffusion from the substrate2014Conference paper (Other academic)
  • 38.
    Donzel-Gargand, Olivier
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fourdrinier, Lionel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Surface defect passivation by a thin metallic barrier for Cu(InxGa1-x)Se2 co-evaporation on Cr-steel substrates2016In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 619, p. 220-226Article in journal (Refereed)
    Abstract [en]

    The use of Cr-steel substrates for the fabrication of Cu(In,Ga)Se2 (CIGS) solar cells is highly desirable and is a topic of considerable research interest. However, solar cells on non-treated steel substrates often exhibit decreased performance compared to their homologues on soda lime glass substrates. This is partly attributed to out-diffusion of steel components (Fe, Cr, Mn, etc.) into the solar cell. To avoid this contamination, thin film barriers can be added on top of the steel surface, but they do not always prevent the diffusion completely. In this paper we study the potential of using Cr and Ti as thin barrier layers. We find that local surface defects on the steel, several micrometers in height, lead to cracks in the back contact as well as in the barrier layers. Advanced transmission electron microscopy (TEM) techniques reveal that elemental diffusion and chemical reactions occur at these openings during heat treatments in Se atmosphere. TEM-energy dispersive X-ray spectroscopy (TEM-EDX) analysis in combination with calculation of the solid state diffusion coefficient demonstrate that a Cr-barrier sacrificially protects the Cr-steel substrate, blocking most of the Fe out-diffusion, whereas a Ti-barrier is less efficient.

  • 39.
    Droulias, Sotirios A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ali, Hasan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Crystal perfection by strain engineering: The case of Fe/V (001)2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 636, p. 608-614Article in journal (Refereed)
    Abstract [en]

    We study the effect of bilayer thickness at fixed volume fraction on the structural quality of Fe/V (001)superlattices. We find that such artificial metallic superlattices can be manufactured with excellent crystalquality and layering up to at least 50 Å in repeat distance (K = LFe +LV). For an intended fixed ratio of theconstituents: LFe/LV= 1/7, out-of-plane coherence lengths comparable to the thicknesses of the sampleswere obtained. We evaluate the strain in- and out-of-plane of both layers as a function of the bilayer thicknessand comment on the growth using the framework of linear elasticity theory. We interpret the stabilityof the superlattice against crystal degradation due to the alternating compressive and tensile strain, yieldingclose to ideal lattice matching to the substrate.

  • 40.
    Edoff, Marika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Viard, Nicolas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wätjen, Jörn Timo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Schleussner, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Westin, Per-Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Sputtering of highly adhesive Mo back contact layers for Cu(In,Ga)Se2 solar cells2009Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    In this work the sputter process for back contact Mo layers was adjusted to increase the adhesive strength of the Mo layers to the glass substrate, while keeping a high deposition rate and high conductivity. Mo layers were fabricated using DC magnetron sputtering in an in-line sputtering system. The adhesive strength was tested with ultrasonic agitation. The combination of good adhesion and high deposition rate was obtained by using a double layer, where the thickness of the first adhesion layer was varied between 25 and 100 nm and sputtered at 15 mTorr, whereas the second bulk layer was varied between 300 and 600 nm and sputtered at 6 mTorr. Solar cells were prepared for all different thicknesses of the adhesive layer and showed similar performance.

  • 41. El-Sayed, Ramy
    et al.
    Bhattacharya, Kunal
    Gu, Zhonglin
    Yang, Zaixing
    Weber, Jeffrey K.
    Li, Hu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Zhao, Yichen
    Toprak, Muhammet S.
    Zhou, Ruhong
    Fadeel, Bengt
    Single-Walled Carbon Nanotubes Inhibit the Cytochrome P450 Enzyme, CYP3A42016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 21316Article in journal (Refereed)
    Abstract [en]

    We report a detailed computational and experimental study of the interaction of single-walled carbon nanotubes (SWCNTs) with the drug-metabolizing cytochrome P450 enzyme, CYP3A4. Dose-dependent inhibition of CYP3A4-mediated conversion of the model compound, testosterone, to its major metabolite, 6β-hydroxy testosterone was noted. Evidence for a direct interaction between SWCNTs and CYP3A4 was also provided. The inhibition of enzyme activity was alleviated when SWCNTs were pre-coated with bovine serum albumin. Furthermore, covalent functionalization of SWCNTs with polyethylene glycol (PEG) chains mitigated the inhibition of CYP3A4 enzymatic activity. Molecular dynamics simulations suggested that inhibition of the catalytic activity of CYP3A4 is mainly due to blocking of the exit channel for substrates/products through a complex binding mechanism. This work suggests that SWCNTs could interfere with metabolism of drugs and other xenobiotics and provides a molecular mechanism for this toxicity. Our study also suggests means to reduce this toxicity, eg., by surface modification.

  • 42.
    Filho, Luimar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    López, Alejandro (Contributor)
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Cogrel, Mathilde (Contributor)
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Leifer, Klaus (Contributor)
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Engqvist, Håkan (Contributor)
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The Effect of Coating Density on Functional Properties of SiNx Coated Implants2019In: Materials, ISSN 1996-1944, Vol. 12, no 20, article id 3370Article in journal (Refereed)
    Abstract [en]

    Ceramic coatings may be applied onto metallic components of joint replacements for improved wear and corrosion resistance as well as enhanced biocompatibility, especially for metal-sensitive patients. Silicon nitride (SiNx) coatings have recently been developed for this purpose. To achieve a high coating density, necessary to secure a long-term performance, is however challenging, especially for sputter deposited SiNx coatings, since these coatings are insulating. This study investigates the time-dependent performance of sputter-deposited SiNx based coatings for joint applications. SiNx coatings with a thickness in the range of 4.3–6.0 µm were deposited by reactive high power impulse magnetron sputtering onto flat discs as well as hip heads made of CoCrMo. SiNx compositional analysis by X-ray photoelectron spectroscopy showed N/Si ratios between 0.8 and 1.0. Immersion of the flat disks in fetal bovine serum solution over time as well as short-term wear tests against ultra-high molecular weight polyethylene (UHMWPE) discs showed that a high coating density is required to inhibit tribocorrosion. Coatings that performed best in terms of chemical stability were deposited using a higher target power and process heating

  • 43.
    Filho, Luimar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Schmidt, Susann
    IHI Ionbond AG, Ind Str 211, CH-4600 Olten, Switzerland;Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Högberg, Hans
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Towards Functional Silicon Nitride Coatings for Joint Replacements2019In: Coatings, ISSN 2079-6412, Vol. 9, no 2, article id 73Article in journal (Refereed)
    Abstract [en]

    Silicon nitride (SiNx) coatings are currently under investigation as bearing surfaces for joint implants, due to their low wear rate and the good biocompatibility of both coatings and their potential wear debris. The aim of this study was to move further towards functional SiNx coatings by evaluating coatings deposited onto CoCrMo surfaces with a CrN interlayer, using different bias voltages and substrate rotations. Reactive direct current magnetron sputtering was used to coat CoCrMo discs with a CrN interlayer, followed by a SiNx top layer, which was deposited by reactive high-power impulse magnetron sputtering. The interlayer was deposited using negative bias voltages ranging between 100 and 900 V, and 1-fold or 3-fold substrate rotation. Scanning electron microscopy showed a dependence of coating morphology on substrate rotation. The N/Si ratio ranged from 1.10 to 1.25, as evaluated by X-ray photoelectron spectroscopy. Vertical scanning interferometry revealed that the coated, unpolished samples had a low average surface roughness between 16 and 33 nm. Rockwell indentations showed improved coating adhesion when a low bias voltage of 100 V was used to deposit the CrN interlayer. Wear tests performed in a reciprocating manner against Si3N4 balls showed specific wear rates lower than, or similar to that of CoCrMo. The study suggests that low negative bias voltages may contribute to a better performance of SiNx coatings in terms of adhesion. The low wear rates found in the current study support further development of silicon nitride-based coatings towards clinical application.

  • 44.
    Fredin, Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Johansson, Erik M. J.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Hedlund, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Using a molten organic conducting material to infiltrate a nanoporous semiconductor film and its use in solid-state dye-sensitized solar cells2009In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 159, no 1-2, p. 166-170Article in journal (Other academic)
    Abstract [en]

    We describe a method to fill thin films of nanoporous TiO2 with solid organic hole-conducting materials and demonstrate the procedure specifically for use in the preparation of dye-sensitized solar cells. Cross-sections of the films were investigated by scanning electron microscopy and it was observed that a hot molten organic material fills pores that are 10 mu m below the surface of the film. We characterized the incident photon to current conversion efficiency properties of the solid TiO2/organic dye/organic hole-conductor heterojunctions and the spectra show that the dye is still active after the melting process.

  • 45.
    Frisk, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ali, Hasan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Composition, structure and magnetic properties of ultra-thin Fe/Ni multilayers sputter deposited on epitaxial Cu/Si(001)2018In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 646, p. 117-125Article in journal (Refereed)
    Abstract [en]

    Sputter deposited symmetric multilayers of (n Fe)/(n Ni), with individual thicknesses from n = 4 to n = 48 monolayers (ML), were deposited on epitaxial Cu/Si(001), and their microstructural evolution and magnetic properties versus n have been studied. Elemental layering can be seen with transmission electron microscopy down to n = 4 ML layer thickness, although an intermixed region characterized by a finite interface width is found to be present. This width is composed of the interface roughness as well as the interdiffusion between layers, but the relative contributions from these two sources could not be concluded by the techniques used. The measured elemental layering and X-ray reflectivity (XRR) give an upper limit to the interface width which must be smaller than the thinnest layers, 4 ML. Electron energy loss spectroscopy (EELS), depth profiling X-ray photoelectron spectroscopy (XPS) and also XRR reveal that Fe has a higher tendency to mix with Ni than vice versa. XPS does not have the resolution to measure this thin elemental layering: composition variations for n = 8 ML which are clearly seen by EELS are barely resolved by XPS. The structure was determined by X-ray diffraction, and an epitaxial fcc (001) structure is found to be maintained throughout the multilayers up to n less than or similar to 8 ML. For larger n values, relaxation starts by Fe-fcc(001) layers changing into Fe-bcc(110), which is then followed by Ni-fcc(001) changing from (001) to (111) orientation along the growth direction. A decreased total measured magnetic moment for the fully epitaxial multilayers can be explained by the fcc Fe layers being partly anti-ferromagnetic, whereas the relaxed multilayers exhibit the expected magnetic properties of (bcc Fe) +(fcc Ni).

  • 46.
    Fu, Le
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xie, Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fu, Wenbo
    Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianshan Road 64, Mianyang, Sichuan 621900, People’s Republic of China.
    Hu, Shuanglin
    Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianshan Road 64, Mianyang, Sichuan 621900, People’s Republic of China.
    Zhang, Zhibin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ultrastrong translucent glass ceramic with nanocrystalline, biomimetic structure2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 11, p. 7146-7154Article in journal (Refereed)
    Abstract [en]

    Transparent/translucent glass ceramics (GCs) have broad applications in biomedicine, armor, energy, and constructions. However, GCs with improved optical properties typically suffer from impaired mechanical properties, compared to traditional sintered full-ceramics. We present a method of obtaining high-strength, translucent GCs by preparing ZrO2-SiO2 nanocrystalline glass ceramics (NCGCs), with a microstructure of monocrystalline ZrO2 nanoparticles (NPs), embedded in an amorphous SiO2 matrix. The ZrO2-SiO2 NCGC with a composition of 65%ZrO2-35%SiO2 (molar ratio, 65Zr) achieved an average flexural strength of 1 GPa. This is one of the highest flexural strength values ever reported for GCs. ZrO2 NPs have a core-shell structure, and the shell is a thin (2–3 nm) amorphous Zr/Si interfacial layer that provides strong bonding between the ZrO2 NPs and SiO2 matrix. The diffusion of Si atoms into the ZrO2 NPs forms a Zr-O-Si superlattice. Electron tomography results show that some of the ZrO2 NPs are connected in one direction, forming in situ ZrO2 nanofibers (with length of ~500 nm), and that the ZrO2 nanofibers are stacked in an ordered way in all three dimensions. The nano-architecture of the ZrO2 nanofibers mimics the architecture of mineralized collagen fibril in cortical bone. Strong interface bonding enables efficient load transfer from the SiO2 matrix to the 3D nano-architecture built by ZrO2 nanofibers and NPs, and the 3D nano-architecture carries the majority of the external load. These two factors synergistically contribute to the high strength of the 65Zr NCGC. This study deepens our fundamental understanding of the microstructure-mechanical strength relationship, which could guide the design and manufacture of other high-strength, translucent GCs.

  • 47.
    Ghajeri, Farnaz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Svenska Aerogel AB.
    Topalian, Zareh
    Svenska Aerogel AB.
    Tasca, Andrea
    University of Strathclyde,Department of Chemical and Process Engineering.
    Jafri, Syed Hassan Mujtaba
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Mirpur University of Science and Technology.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Norberg, Peter
    Svenska Aerogel AB, R&D.
    Sjöström, Christer
    Svenska Aerogel AB.
    Case Study of a Green Nanoporous Material from Synthesis to Commercialisation: Quartzene®2018In: Current Opinion in Green and Sustainable Chemistry, ISSN 2452-2236, Vol. 12, p. 101-109Article in journal (Refereed)
    Abstract [en]

    Synthetic amorphous silicas with high porosity (94–97%) are introduced and various pathways for their synthesis are presented. The materials have structures with high surface area (300–750 m2/g) and are commercialised under the name of Quartzene®. Low cost silica sources and ambient pressure drying enable production in large scale with approximately 70% cost reduction as compared to conventional method silica aerogels. The structure is analysed, properties are reported as low density (0.04–0.15 g/ml), low thermal conductivity (24–26 mW/m·K), etc. Formaldehyde gas adsorption tests reveal that the uptake level of samples made by Quartzene® is significantly increased as compared to commercially available adsorbents. Thermal conductivity at elevated temperatures for mixtures of Quartzene® and stone wool shows a 23% reduction at 650 °C as compared to pure stone wool. Scaling up process for this green material meeting environmental sustainability demands in industrial manufacturing is discussed and challenges/current developments are presented.

  • 48.
    Giraldo, Sergio
    et al.
    Catalonia Institute for Energy Research (IREC).
    Neuschitzer, Markus
    Catalonia Institute for Energy Research (IREC).
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lopez-Marino, Simon
    Catalonia Institute for Energy Research (IREC).
    Sanchez, Yudania
    Catalonia Institute for Energy Research (IREC).
    Xie, Haibing
    Catalonia Institute for Energy Research (IREC).
    Colina, Monica
    Catalonia Institute for Energy Research (IREC).
    Placidi, Marcel
    Catalonia Institute for Energy Research (IREC).
    Pistor, Paul
    Catalonia Institute for Energy Research (IREC).
    Izquierdo-Roca, Victor
    Catalonia Institute for Energy Research (IREC).
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Perez-Rodriguez, Alejandro
    Universitat de Barcelona.
    Saucedo, Edgardo
    Catalonia Institute for Energy Research (IREC).
    Large Efficiency Improvement in Cu2ZnSnSe4 Solar Cells by Introducing a Superficial Ge Nanolayer2015In: Advanced Energy Materials, ISSN 1614-6840, Vol. 5, no 21, article id 1501070Article in journal (Refereed)
    Abstract [en]

    A large improvement of Cu2ZnSnSe4 solar cell efficiency is presented based on the introduction of a Ge superficial nanolayer. This improvement is explained by three complementary effects: the formation of a liquid Ge-related phase, the possible reduction of Sn multicharge states, and the formation of GeOx nanoinclusions, which lead to an impressive solar cell (VOC) increase.

  • 49.
    Giraldo, Sergio
    et al.
    Catalonia Inst Energy Res, Jardins Dones Negre 1, St Adria De Besos 08930, Barcelona, Spain..
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Larramona, Gerardo
    IMRA Europe SAS, 220 Rue Albert Caquot, F-06904 Sophia Antipolis, France..
    Neuschitzer, Markus
    Catalonia Inst Energy Res, Jardins Dones Negre 1, St Adria De Besos 08930, Barcelona, Spain..
    Pistor, Paul
    Catalonia Inst Energy Res, Jardins Dones Negre 1, St Adria De Besos 08930, Barcelona, Spain..
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Perez-Rodriguez, Alejandro
    Catalonia Inst Energy Res, Jardins Dones Negre 1, St Adria De Besos 08930, Barcelona, Spain.;Univ Barcelona, IN2UB, C Marti & Franques 1, E-08028 Barcelona, Spain..
    Moisan, Camille
    IMRA Europe SAS, 220 Rue Albert Caquot, F-06904 Sophia Antipolis, France..
    Dennler, Gilles
    IMRA Europe SAS, 220 Rue Albert Caquot, F-06904 Sophia Antipolis, France..
    Saucedo, Edgardo
    Catalonia Inst Energy Res, Jardins Dones Negre 1, St Adria De Besos 08930, Barcelona, Spain..
    Cu2ZnSnSe4 solar cells with 10.6% efficiency through innovative absorber engineering with Ge superficial nanolayer2016In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 24, no 10, p. 1359-1367Article in journal (Refereed)
    Abstract [en]

    In our recently published work, the positive effect of a Ge nanolayer introduced into the processing of Cu2ZnSnSe4 absorbers (CZTSe) was demonstrated. In this contribution, the complete optimization of this new approach is presented for the first time. Hence, the optimum Ge nanolayer thickness range is defined in order to achieve an improved performance of the devices, obtaining a record efficiency of 10.6%. By employing this optimized approach, the open-circuit voltage (V-OC) is boosted for our pure selenide CZTSe up to 489 mV, leading to V-OC deficit among the lowest reported so far in kesterite technology. Additionally, two important effects related to the Ge are unambiguously demonstrated that might be the origin of the V-OC boost: the improvement of the grain size and the corresponding crystalline quality, and the interaction between Ge and Na that allows for dynamic control over the CZTSe doping. Finally, evidences pointing to the origin of the deterioration of devices properties for large Ge concentrations are presented.

  • 50.
    Hajati, Y
    et al.
    Dept of Physics, Faculty of Sciences, University of Shahid Chamran, Ahwaz, Iran.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, S H M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Haldar, Soumyajyoti
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bhandary, Sumanta
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Shoushtari, M Z
    Dept of Physics, Faculty of Sciences, University of Shahid Chamran, Ahwaz, Iran.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Improved gas sensing activity in structurally defected bilayer graphene2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 50, p. 50550-Article in journal (Refereed)
    Abstract [en]

    Graphene is a two-dimensional material with a capability of gas sensing, which is here shown to be drastically improved by inducing gentle disorder in the lattice. We report that by using a focused ion beam technique, controlled disorder can be introduced into the graphene structure through Ga + ion irradiation. This disorder leads to an increase in the electrical response of graphene to NO 2 gas molecules by a factor of three in an ambient environment (air). Ab initio density functional calculations indicate that NO 2 molecules bind strongly to Stone–Wales defects, where they modify electronic states close to the Fermi level, which in turn influence the transport properties. The demonstrated gas sensor, utilizing structurally defected graphene, shows faster response, higher conductivity changes and thus higher sensitivity to NO 2 as compared to pristine graphene.

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