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  • 1.
    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)
  • 2.
    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)
  • 3.
    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.
    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.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Systematic assessment of trapped gold nanoparticles in a nanogap platform for electrical characterization of conducting and non-conducting moleculesManuscript (preprint) (Other academic)
  • 4.
    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)
  • 5.
    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)
  • 6.
    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)
  • 7.
    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.

  • 8.
    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)
  • 9.
    Blom, Tobias
    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.
    Körber, N.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Fabrication and characterization of high resistance sub-5 nm gaps made by electrodeposition of gold in 30 nm gaps cut by using a focused gallium ion beamManuscript (preprint) (Other academic)
  • 10.
    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)
  • 11.
    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.

  • 12.
    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.

  • 13.
    Jafri, Hassan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    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.
    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.
    Using a nano-contact platform for evaluating molecular electronics response2009Conference paper (Other academic)
  • 14.
    Jafri, Hassan
    et al.
    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.
    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.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Systematic assessment of a nanoparticle bridge platform for molecular electronics measurementsManuscript (preprint) (Other academic)
    Abstract [en]

    A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles (AuNPs) in order to make electrical measurements and assess the platform under ambient conditions. Initially bare electrodes were tested to determine the response of the platform and it was found that creating devices in ambient conditions requires careful cleaning processes and awareness of the contributions contaminants may make to measurements. Both octanethiol (OT) and Biphenyldithiol (BPDT) molecules were also tested by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with the nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal-molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density function theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve when preparing the devices in ambient conditions. Significant hysteresis, or conductance switching, in the I-V curves of BPDT was also observed, which we attribute primarily to voltage induced changes at the interface between the molecule and the metal.

  • 15.
    Jafri, Hassan
    et al.
    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.
    Widenqvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Carva, Karel
    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.
    Eriksson, Olle
    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.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Quinlan, R.A.
    College of William and Mary, US.
    Holloway, B.
    Luna Innovations Incorporated.
    Surpi, Alessandro
    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.
    Control of Conductivity in Graphene by Formation of Defects2008In: AVS 55th International Symposium & Exhibition 2008, October 19-24, Boston, USA, 2008Conference paper (Refereed)
    Abstract [en]

    Due to their large surface areas, the conductivity of graphene and carbonnano-sheets depends strongly on their chemical environment. This is thebase for future environmental sensors containing graphene sheets. Here, abinitiocalculations propose a possibility of conductivity increase. In theexperiment, a 1-2 orders of magnitude increase of the conductivity isobserved experimentally on sub-nanometTe carbon nano-sheets by using anin-situ nano-manipulation set-up. The conductivity of the graphene sheetswas assessed from first-principle simulations. Insertion of defects in thegraphene sheets can lead to a strong increase of the conductivity of singlegraphene sheets. To study this result experimentally, we carried outconductivity measurements on sub-nanometre graphene nano-sheets that aredeposited on W -substrates by radio-frequency plasma-enhanced chemicalvapour deposition. This deposition process creates free-standingmicrometer-sized carbon nano-sheets with sub-nanometre thickness. Thesenano-sheets were exposed to an acid treatment. It has been shown recentlythat such acid treatment creates defects in these sheets. Using a nanomanipulatorinside a scanning electron microscope, we individuallycontacted the nano-sheets and measured their resistance as a function oftheir functionalization. From more than 1000 measurements we obtain a 1-2order of magnitude increase of conductivity in the functionalised carbonnano-sheets as compared to just water treated or untreated carbon nanosheets.This result corresponds well to the conductivity change obtainedfrom theory. This study makes it possible to create environmental sensorsbased on graphene like carbon nano-sheets.

  • 16.
    Jafri, Hassan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Biplab, Sanyal
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Quinlan, Ronald A.
    Holloway, Brian C.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Electrical characterization of defect induced graphene nanosheets2009In: Nanotech Europe 2009 - 28-30 september Berlin, 2009Conference paper (Refereed)
  • 17.
    Jafri, Hassan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Grenberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Holloway, B.C.
    Quinlan, R.A.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Conductivity engineering of graphene and carbon nanosheets by defect formation2008In: Conference of the American Vacuum Society, Boston, 2008, 2008Conference paper (Refereed)
  • 18.
    Jafri, Hassan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Sanyal, Biplab
    Fransson, Jonas
    Eriksson, Olle
    Jansson, Ulf
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Karis, Olof
    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.
    The effect of induced vacancy defects on resistivity of graphene2009In: Scandem conference, Reykjavik 2009, 2009Conference paper (Refereed)
  • 19.
    Jafri, Hassan M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jonas, Fransson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Physical Organic Chemistry.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Identification of vibrational signatures from short chains of interlinked molecule-nanoparticle junctions obtained by inelastic electron tunnelling spectroscopy2013In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 5, no 11, p. 4673-4677Article in journal (Refereed)
    Abstract [en]

    Short chains containing a series of metal- molecule-nanoparticle nanojunctions are a nano-materials system with the potential to give electrical signatures close to those from single molecule experiments while enabling to build portable devices on a chip. Inelastic electron tunnelling spectroscopy (IETS) measurements provide one of the most characteristic electrical signals of single and few molecules. In interlinked molecule-nanoparticle (NP) chains containing of typically 5-7 molecules in a chain, the spectrum is expected to be a superposition of the vibrational signature of individual molecules. We have established a stable and reproducible molecule-AuNP multi-junction by placing few 1,8-octanedithiol (ODT) molecules into a versatile and portable nanoparticle-nanoelectrode platform and measured for the first time vibrational molecular signatures complex and coupled few-molecule-NP junctions. From quantum transport calculations, we model the IETS spectra and identify vibrational modes as well as the number of molecules contributing to the electron transport in the measured spectra.

  • 20.
    Jafri, S. Hassan M.
    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.
    Blom, Tobias
    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.
    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.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Assessment of a nanoparticle bridge platform for molecular electronics measurements2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 43, p. 435204-Article in journal (Refereed)
    Abstract [en]

    A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles in order to make electrical measurements and assess the platform under ambient conditions. Non-functionalized electrodes were tested to determine the intrinsic response of the platform and it was found that creating devices in ambient conditions requires careful cleaning and awareness of the contributions contaminants may make to measurements. The platform was then used to make measurements on octanethiol (OT) and biphenyldithiol (BPDT) molecules by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal–molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density functional theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve under ambient conditions. Significant hysteresis in the IV curves of BPDT was also observed, which was attributed primarily to voltage induced changes at the interface between the molecule and the metal.

  • 21.
    Jafri, S Hassan M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Welch, Ken
    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.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Control of junction resistances in molecular electronic devices fabricated by FIB2011In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 88, no 8, p. 2629-2631Article in journal (Refereed)
    Abstract [en]

    A major hurdle to realize molecular electronic devices (MEDs) is to make reliable electrical contacts to a single or a few molecules. Our nano-contact platform with a gap size of less than 25 nm with resistances above 1000 TΩ was built using combined techniques of photolithography, electron beam lithography and focused ion beam milling. In this study, we have used gold nanoparticles (AuNPs) to bridge the nanoelectrode gaps by dielectrophoretic trapping and thus obtain electrical contacts. The electrodes and/or the nanoparticles were functionalised with 1–2 nm long alkane-thiol molecules so that the electronic structure of these molecules determines the properties of the electrical junction. Molecules were introduced both by functionalising the nanogap and the nanoparticles and the results of both functionalisation protocols are compared. Here, we show the nanogap–nanoparticle bridge set-up containing metal–molecule junctions that can be used as a base for the development of molecular electronics containing only a few molecules under ambient conditions. Current–voltage (IV) characterization of alkanethiol/gold junction showed non-linear response where mean geometric resistance of four different junctions could be tuned from 20 GΩ to 20 TΩ. The results from the measurements on 1-alkanethiol in such devices is a first step to demonstrate that this platform has the potential to obtain stable electronic devices having relatively small numbers of molecules with reliable metal molecule junction by combing top-down and bottom-up approaches.

  • 22.
    Jafri, S. Hassan M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Department of Electrical Engineering, Mirpur University of Science and Technology, Pakistan.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala Univ, Dept Chem BMC, SE-75123 Uppsala, Sweden..
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nano-fabrication of molecular electronic junctions by targeted modification of metal-molecule bonds2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 14431Article in journal (Refereed)
    Abstract [en]

    Reproducibility, stability and the coupling between electrical and molecular properties are central challenges in the field of molecular electronics. The field not only needs devices that fulfill these criteria but they also need to be up-scalable to application size. In this work, few-molecule based electronics devices with reproducible electrical characteristics are demonstrated. Our previously reported 5 nm gold nanoparticles (AuNP) coated with omega-triphenylmethyl (trityl) protected 1,8-octanedithiol molecules are trapped in between sub-20 nm gap spacing gold nanoelectrodes forming AuNP-molecule network. When the trityl groups are removed, reproducible devices and stable Au-thiol junctions are established on both ends of the alkane segment. The resistance of more than 50 devices is reduced by orders of magnitude as well as a reduction of the spread in the resistance histogram is observed. By density functional theory calculations the orders of magnitude decrease in resistance can be explained and supported by TEM observations thus indicating that the resistance changes and strongly improved resistance spread are related to the establishment of reproducible and stable metal-molecule bonds. The same experimental sequence is carried out using 1,6-hexanedithiol functionalized AuNPs. The average resistances as a function of molecular length, demonstrated herein, are comparable to the one found in single molecule devices.

  • 23.
    Jafri, S.H. M
    et al.
    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, Applied Materials Sciences.
    Wallner, Andreas
    Ottosson, Henrik
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Stability optimisation of molecular electronic devices based on nanoelectrode–nanoparticle bridge platform in air and different storage liquids2014In: Journal of nanoparticle research, Vol. 16, no 12, p. 1-11Article in journal (Refereed)
  • 24.
    Jafri, S.Hassan M.
    et al.
    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.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical 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.
    Control of junction resistances in molecular electronic devices fabricated by FIB2010In: 36th International Conference on Micro and Nano Engineering, MNE2010, Italy (2010), 2010Conference paper (Refereed)
    Abstract [en]

    Molecules provide an opportunity to fabricate electronic devices with much smaller basic unit in size i.e. 1-5 nm as compared to today’s silicon based electronics. Furthermore, molecules can be synthesized withalmost unlimited variation of their electronic structure. Theoretically, molecules in various configurations were demonstrated as rectifiers, transistors or memories, but experimentally it is still very difficult to obtaina  stable and reproducible molecular based device [1]. A major hurdle to realize such devices is to make reliable electrical contacts to a single or a few molecules. Here, we show the first reproducible and systematic evaluation of a nanogap-nanoparticle bridge set-up that can be used as base for development of few molecule molecular electronics under ambient conditions. We have developed a nano-contact platform by top-down approach [2] with a gap size of 20-30nm using combined techniques of photolithography, electron beam lithography and focused ion beam milling (Fig 1). These gaps demonstrate excellent resistance in order of 1000 TΩ enabling us to carry out electrical characterization of highly resistive nanomaterials.However, compared to the size of molecules these gaps are quite big. In this study, we used metallic nanoparticles to bridge the gap and thus obtain electrical contacts with 1-2nm long molecules in the junction between the nanoelectrodes and the nanoparticles. The nanoparticles are assembled in the gap  by a bottom-up approach using dielectrophrosis trapping process. Prior to introduction of molecules in such devices, we found that the trapping of gold nanoparticles (AuNP) in between clean nanoelectrodes without presence of molecules often gave resistance in order of mega-ohms to giga-ohms due to presence of a non conductive barrier. However, it was observed that cleaning protocols of both the gold contacts and nanoparticles in solution lead to resistance of less than a few hundreds of ohms (Fig 2). Molecules were introduced both by functionalizing the electrode gap and the the nanoparticles and the results of both functionalisation protocols are compared. By optimizing the electrode cleaning as well as the functionalisation of the metallic surfaces, we obtain reproducible electrical measurements. We fabricated such devices either by depositing a Self Assembled Monolayer (SAM) of molecules on the nano-contacts and bridging the gap by AuNP or by bridging the clean nano-contacts with molecule-coated-AuNP (Fig 3). Here we utilized a model molecules octanethiol (OT), octanedithiol and biphenyldithiol in fabrication of devices and study of metal molecule junction resistance. IV characterization of OT molecules (Fig 4) showed linear response where current levels varied between picoamps and femtoamps with an applied voltage of 1-3V. OT in this setup had one physisorbed contact with gold, which resulted in much less wave function mixing at the molecule-metal interface, and consequently decreased the transmission probability at the molecule-electrode interface. As a result, in the evaluation of more than 50 devices, a considerable variation of resistance between different devices due to the lack of covalent binding, the variation in number of trapped AuNPs, incomplete coverage of OT on the uneven surface of nanoelectrodes and variation in contact surface geometry. Density functional theory is used to understand the origin of the resistance fluctuation. We were able to estimate the average resistance per octanethiol molecule for such device in order of 175GΩ, in good agreement with other published results. Our results with the measurements on OT in such devices demonstrate that it is possible to fabricate stable electronic devices having relatively small numbers of molecules with reliable metal molecule junction by combing top-down and bottom-up approaches. By functionalizing the nanoparticles, we obtained a strong decrease of the resistance spread of such devices from 3 orders of magnitude to about 1 order of magnitude, making this technology a potential approach for molecular devices operating at ambient conditions.

     

  • 25.
    Jafri, S.Hassan M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Realization of highly reproducible molecular junctions in a nanoparticle-alkanedithiol-nanoelectrode bridge platformManuscript (preprint) (Other academic)
  • 26.
    Jafri, Syed Hassan Mujtaba
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Stability optimisation of molecular electronic devices based on nanoelectrode-nanoparticle bridge platform in air and different storage liquids2014In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 16, no 12, p. 2811-Article in journal (Refereed)
    Abstract [en]

    The long-term stability of metal nanoparticle-molecule junctions in molecular electronic devices based on nanoelectrodes (NEL) is a major challenge in the effort to bring related molecular electronic devices to application. To optimize the reproducibility of molecular electronic nanodevices, the time-dependent modification of such junctions as exposed to different media needs to be known. Here, we have studied (1) the stability of Au-NEL and (2) the electrical stability of molecule-Au nanoparticle (AuNP) junctions themselves with the molecule being 1,8-octanedithiol (ODT). Both the NELs only and the junctions were exposed to air and liquids such as deionized water, tetrahydrofuran, toluene and tetramethylethylenediamine (TMEDA) over a period of 1 month. The nanogaps remained stable in width when stored in either deionized water or toluene, whereas the current through 1,8-octanedithiol-NP junctions remained most stable when stored in TMEDA as compared to other solvents. Although it is difficult to follow the chemical processes in such devices in the 10-nm range with analytical methods, the behavior can be interpreted from known interactions of solvent molecules with electrodes and ODT.

  • 27.
    Jafri, Syed Hassan Mujtaba
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    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.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nanoparticle Bridges for Studying Electrical Properties of Organic Molecules2012In: Nanoparticles in Biology and Medicine: / [ed] Soloviev, M., Springer Publishing Company, 2012, p. 535-546Chapter in book (Refereed)
  • 28.
    Jafri, Syed Hassan Mujtaba
    et al.
    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 Materials Science.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Quinlan, Ronald A
    College of William and Mary, Williamsburg VA, USA.
    Holloway, Brian C
    Luna Innovations, Danville, VA, USA.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Conductivity engineering of graphene by defect formation2010In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 43, no 4, p. 045404-Article in journal (Refereed)
    Abstract [en]

    Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, by more than one order of magnitude. We obtain a pronounced enhancement of the conductivity after insertion of defects by both quantum mechanical transport calculations as well as experimental studies of carbon nano-sheets. Our finding is attributed to the defect induced mid-gap states, which create a region exhibiting metallic behaviour around the vacancy defects. The modification of the conductivity of graphene by the implementation of stable defects is crucial for the creation of electronic junctions in graphene-based electronics devices.

  • 29.
    Leifer, Klaus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    Jafri, Hassan
    Carva, K.
    Sanyal, B.
    Grennberg, H.
    Jansson, U.
    Eriksson, O.
    Modification of electrical properties graphene by of defect insertion2011In: Proceedings Graphene Workshop, Bilbao, Spain, 2011., Spain: Graphene Workshop, Bilbao, Spain, 2011. , 2011Conference paper (Refereed)
  • 30.
    Leifer, Klaus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    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.
    Carva, K.
    Sanyal, B.
    Grennberg,, H.
    Jansson,, U.
    Holloway,, B.C.
    Quinlan,, R.
    Eriksson, O.
    Control of Conductivity in Graphene by Formation of Defects2010Conference paper (Refereed)
  • 31.
    Leifer, Klaus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    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.
    Löfås, H.
    Grigoriev, A.
    Ahuja, R.
    Wallner, A.
    Ottosson, H.
    Use of a nanoelectrode nanoparticle bridge platform in molecular electronics2010Conference paper (Refereed)
  • 32.
    Leifer, Klaus
    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.
    Blom, Tobias
    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.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Use of a nanoelectrode nanoparticle bridge platform in molecular electronics2010In: ElecMol’10, 5th International Meeting on Molecular Electronics, Grenoble, France, December 6-10, 2010, 2010, p. 116-116Conference paper (Refereed)
  • 33.
    Leifer, Klaus
    et al.
    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.
    Jafri, S.H. M
    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, Experimental Physics.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Molecular electronics on non-perfect electrode surfaces2010In: International Conference on Molecular Electronics, Emmetten, Switzerland, 2010Conference paper (Refereed)
  • 34.
    Leifer, Klaus
    et al.
    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.
    Jafri, S.Hassan M.
    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.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    FIB Fabrication and use of high resistance nanogaps for application in molecular electronics2010In: 17th International Microscopy Congress, IMC17, Brazil, 2010Conference paper (Refereed)
  • 35.
    Leifer, Klaus
    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.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Widenqvist, E
    Carva, Karel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Eriksson, Olle
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Quinlan, R
    Holloway, B
    Luna Innovations Incorporated, NanoWorks Division,521 Bridge Street, Danville, 24541, Virginia, USA.
    Surpi, A
    Control of Conductivity in Graphene by Formation of Defects2008Conference paper (Refereed)
  • 36.
    Leifer, Klaus
    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.
    Löfås, H.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hayat, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fransson, J.
    Wallner, A.
    Ottosson, H.
    Grigoriev, A.
    Ahuja, R.
    A 10-nm sized molecular electronics platform for applied and fundamental molecular property measurements2012In: Proceedings of Elecmol conference, Grenoble, 2012., Grenoble, 2012Conference paper (Refereed)
  • 37.
    Leifer, Klaus
    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.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Daukiya, Lakshya
    Vonau, François
    Simon, Laurent
    Structural, electrical and sensing properties of defected graphene2014In: Structural, electrical and sensing properties of defected graphene, 2014Conference paper (Other academic)
  • 38.
    Leifer, Klaus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Li, Hu
    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, Experimental Physics.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Daukiya, Lakshya
    Vonau, François
    Simon, Laurent
    Structural, electrical and sensing properties of defected graphene2014Conference paper (Refereed)
  • 39.
    Leifer, Klaus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Muranaka, T.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ziemann, V.
    ANALYSIS OF A COPPER SAMPLE FOR THE CLIC ACS STUDYIN A FIELD EMISSION SCANNING MICROSCOPE2011In: CERNArticle in journal (Refereed)
  • 40.
    Leifer, Klaus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Akhtar, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    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.
    Electrical measurements on graphene in a Au-nanoparticle-bridge platform2010Conference paper (Refereed)
  • 41.
    Muranaka, Tomoko
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Leifer, K
    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.
    In-situ Experiments of Vacuum Discharge using Scanning Electron Microscopes2011Conference paper (Refereed)
  • 42.
    Muranaka, Tomoko
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Blom, Tobias
    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.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Instrumental developments for in situ breakdown experiments inside a scanning electron microscope2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 657, no 1, p. 122-125Article in journal (Refereed)
    Abstract [en]

    Electrical discharges in accelerating structures are one of the key issues limiting the performance of future high energy accelerators such as the Compact Linear Collider (CLIC). Fundamental understanding of breakdown phenomena is an important part of the CLIC feasibility study. The present work concerns the experimental study of breakdown using Scanning Electron Microscopes (SEMs). An SEM gives us the opportunity to achieve high electrical gradients of 1 kV/mu m which corresponds to 1 GV/m by exciting a probe needle with a high voltage power supply and controlling the positioning of the needle with a linear piezo motor. The gap between the needle tip and the surface is controlled with sub-micron precision. A second electron microscope equipped with a Focused Ion Beam (FIB) is used to create surface corrugations and to sharpen the probe needle to a tip radius of about 50 nm. Moreover it is used to prepare cross-sections of a voltage breakdown area in order to study the geometrical surface damages as well as the elemental composition of the breakdown.

  • 43.
    Rubino, Stefano
    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.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Carva, Karel
    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.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Quinlan, Ronald A.
    Department of Applied Science, The College of William and Mary, 325 McGlothin Street Hall, Williamsburg, VA 23187, USA.
    Holloway, Brian C.
    Department of Applied Science, The College of William and Mary, 325 McGlothin Street Hall, Williamsburg, VA 23187, USA.
    Lidbaum, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Oppeneer, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Liebig, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Schattschneider, Peter
    Institute for Solid State Physics, Vienna University of Technology.
    Stöger-Pollach, Michael
    University Service Center for Transmission Electron Microscopy, Vienna University of Technology.
    Hurm, Christian
    NWF II - Physik, University of Regensburg, D - 93040 Regensburg, Germany.
    Zweck, Josef
    NWF II - Physik, University of Regensburg, D - 93040 Regensburg, Germany.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    In-situ contacting of nanosheets and remote EMCD2009In: 2nd International Workshop on Remote Electron Microscopy and In Situ Studies, Gothenburg, Sweden 16-18 November 2009, 2009Conference paper (Other academic)
  • 44.
    Sugunan, Abhilash
    et al.
    Royal Institue of Technology (KTH).
    Jafri, S. Hassan M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Qin, Jian
    Royal Institue of Technology (KTH).
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Toprak, Muhammet S.
    Royal Institue of Technology (KTH).
    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.
    Muhammed, Mamoun
    Royal Institue of Technology (KTH).
    Low-temperature synthesis of photoconducting CdTe nanotetrapods2010In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, no 6, p. 1208-1214Article in journal (Refereed)
    Abstract [en]

    We show that CdTe nanotetrapods are formed by two distinct growth regimes depending on the reaction temperature. At a low temperature (180 C) the combination of slow reaction kinetics and Ostwald ripening results in a novel pathway for the formation of a tetrapodal morphology. We also report, to the best of our knowledge, the first direct evaluation of the photoconductivity of CdTe nanotetrapods by employing gold ‘nanogap’ electrodes that were fabricated in-house. Our preliminary findings include I–V responses showing current enhancement, due to illumination, of up to 100 times.

  • 45.
    Wallner, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Physical Organic Chemistry.
    Jafri, S. Hassan M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Baumgartner, Judith
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Formation and NMR Spectroscopy of ω-Thiol Protected α,ω-Alkanedithiol Coated Gold Nanoparticles and Their Usage in Molecular Charge Transport Junctions2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 14, p. 9057-9067Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticles (AuNPs) coated with stabilizing molecular monolayers are utilized in areas ranging from life sciences to nanoelectronics. Here we present a novel and facile one-pot single phase procedure for the preparation of stable AuNPs with good dispersity, which are coated with α,ω-alkanedithiols whose outer ω-thiol is protected by a triphenylmethyl group. Using dielectrophoresis we were able to trap these AuNPs, coated with ω-thiol protecting groups, in a 20 nm gold electrode nanogap. The ω-thiol group was then deprotected under acidic conditions in situ once the AuNPs were correctly positioned in the device. The subsequent deprotection resulted in an increase of conductance by three orders of magnitude, indicating that the isolated dithiol coated AuNPs were fused into a covalently bonded network with AuNP-molecule-AuNP as well as electrode-molecule-AuNP linkages. Furthermore, complete characterization of the AuNP surface-bonded alkanedithiols was achieved using a series of one- and two-dimensional NMR spectroscopy techniques. Our spectra of the molecule-coated AuNPs show well resolved signals, only slightly broader than for free molecules in solution, in contrast to many earlier reported NMR spectral data of molecules attached to AuNPs. Complementary diffusion NMR spectroscopic experiments were performed to prove that the observed alkanedithiols are definitely surface bonded species and do not exist in free and unattached form.

  • 46.
    Welch, Ken
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Blom, Tobias
    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.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Enabling measurements of low-conductance single molecules using gold nanoelectrodes2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 12, p. 125707-Article in journal (Refereed)
    Abstract [en]

    A high resistance nanogap platform was used to trap and electrically characterize 30 nm thiolated double-stranded DNA molecules. High resolution scanning electron microscopy was also used to image the trapped DNA strands. It was found that the surface state of the electrodes and underlying substrate could influence the measurements of trapped molecules when the measured resistances were on the order of TΩ or greater. Hydrophilic surfaces gave rise to larger leakage currents that could potentially mask the underlying signals from molecules positioned in the nanogap. Finally, the careful handling of the samples and control of the environment is essential to avoid surface charging of the oxide substrate layer as these parasitic charges affect electrical measurements of the nanogap. The presented results thus outline some important considerations when making low-conductance measurements on molecules and should prove useful for the characterization of molecules in molecular electronics or sensors employing nanogap platforms.

  • 47.
    Welch, Ken
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Blom, Tobias
    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.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Measurements of low-conductance single molecules using gold nanoelectrodes: limitations and considerationsManuscript (preprint) (Other academic)
    Abstract [en]

    A high resistance nanogap platform was used to trap and electrically characterize 30 nm thiolated double-stranded DNA molecules. High resolution scanning electron microscopy was also used to image the trapped DNA strands. It was found that the surface state of the electrodes and underlying substrate could influence the measurements of trapped molecules when measured resistances were on the order of TW or greater. Hydrophilic surfaces gave rise to larger leakage currents that could potentially mask underlying signals from molecules positioned in the nanogap. Finally, careful handling of the samples and control of the environment is essential to avoid surface charging of the oxide substrate layer as these parasitic charges affect electrical measurements of the nanogap. The presented results should be useful for characterization of molecules in molecular electronics or sensors employing nanogap platforms.

  • 48. Yang, Liang
    et al.
    Hedhammar, My
    Blom, Tobias
    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, Experimental Physics.
    Johansson, Jan
    Habibovic, Pamela
    van Blitterswijk, Clemens A.
    Biomimetic calcium phosphate coatings on recombinant spider silk fibres2010In: Biomedical Materials, ISSN 1748-6041, Vol. 5, no 4, p. 045002-Article in journal (Refereed)
    Abstract [en]

    Calcium phosphate ceramic coatings, applied on surfaces of metallic and polymeric biomaterials, can improve their performance in bone repair and regeneration. Spider silk is biocompatible, strong and elastic, and hence an attractive biomaterial for applications in connective tissue repair. Recently, artificial spider silk, with mechanical and structural characteristics similar to those of native spider silk, has been produced from recombinant minispidroins. In the present study, supersaturated simulated body fluid was used to deposit calcium phosphate coatings on recombinant spider silk fibres. The mineralization process was followed in time using scanning electron microscopy equipped with an energy dispersive x-ray (EDX) detector and Raman spectroscope. Focused ion beam technology was used to produce a cross section of a coated fibre, which was further analysed by EDX. Preliminary in vitro experiments using a culture of bone marrow-derived human mesenchymal stem cells (hMSCs) on coated fibres were also performed. This study showed that recombinant spider silk fibres were successfully coated with a homogeneous and thick crystalline calcium phosphate layer. In the course of the mineralization process from modified simulated body fluid, sodium chloride crystals were first deposited on the silk surface, followed by the deposition of a calcium phosphate layer. The coated silk fibres supported the attachment and growth of hMSCs.

1 - 48 of 48
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