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  • 101.
    Lischner, Johannes
    et al.
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA.;Univ London Imperial Coll Sci Technol & Med, Dept Phys, London SW7 2AZ, England.;Univ London Imperial Coll Sci Technol & Med, Dept Mat, London SW7 2AZ, England.;Univ London Imperial Coll Sci Technol & Med, Thomas Young Ctr Theory & Simulat Mat, London SW7 2AZ, England..
    Nemsak, Slavomir
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA.;Univ Calif Davis, Dept Phys, Davis, CA 95616 USA.;Forschungszentrum Julich, Peter Gruenberg Inst 6, D-52425 Julich, Germany..
    Conti, Giuseppina
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA.;Univ Calif Davis, Dept Phys, Davis, CA 95616 USA..
    Gloskovskii, Andrei
    Deutsch Elektronen Synchrotron DESY, Photon Sci, Notkestr 85, D-22607 Hamburg, Germany..
    Pálsson, Gunnar Karl
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA.;Univ Calif Davis, Dept Phys, Davis, CA 95616 USA..
    Schneider, Claus M.
    Forschungszentrum Julich, Peter Gruenberg Inst 6, D-52425 Julich, Germany..
    Drube, Wolfgang
    Deutsch Elektronen Synchrotron DESY, Photon Sci, Notkestr 85, D-22607 Hamburg, Germany..
    Louie, Steven G.
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA..
    Fadley, Charles
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA.;Univ Calif Davis, Dept Phys, Davis, CA 95616 USA..
    Accurate determination of the valence band edge in hard x-ray photoemission spectra using GW theory2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, nr 16, artikel-id 165703Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce a new method for determining accurate values of the valence-band maximum in x-ray photoemission spectra. Specifically, we align the sharpest peak in the valence-band region of the experimental spectrum with the corresponding feature of a theoretical valence-band density of states curve from ab initio GW theory calculations. This method is particularly useful for soft and hard x-ray photoemission studies of materials with a mixture of valence-band characters, where strong matrix element effects can render standard methods for extracting the valence-band maximum unreliable. We apply our method to hydrogen-terminated boron-doped diamond, which is a promising substrate material for novel solar cell devices. By carrying out photoemission experiments with variable light polarizations, we verify the accuracy of our analysis and the general validity of the method. Published by AIP Publishing.

  • 102.
    Long, Debing
    et al.
    Hubei Univ, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Key Lab Green Preparat & Applicat Funct Mat, Fac Mat Sci & Engn,Minist Educ, Wuhan 430062, Hubei, Peoples R China..
    Li, Mingkai
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Hubei Univ, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Key Lab Green Preparat & Applicat Funct Mat, Fac Mat Sci & Engn,Minist Educ, Wuhan 430062, Hubei, Peoples R China..
    Meng, Dongxue
    Hubei Univ, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Key Lab Green Preparat & Applicat Funct Mat, Fac Mat Sci & Engn,Minist Educ, Wuhan 430062, Hubei, Peoples R China..
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    He, Yunbin
    Hubei Univ, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Key Lab Green Preparat & Applicat Funct Mat, Fac Mat Sci & Engn,Minist Educ, Wuhan 430062, Hubei, Peoples R China..
    Theoretical investigation of the structural, electronic, and thermodynamic properties of CdS1-xSex alloys2018Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, nr 10, artikel-id 105103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the structural, electronic, and thermodynamic properties of wurtzite (WZ) and zincblende (ZB) CdS1-xSex alloys are investigated using the density functional theory (DFT) and the cluster expansion method. A special quasirandom structure containing 16 atoms is constructed to calculate the band structures of random alloys. The band gaps of CdS1-xSex alloys are direct and decrease as the Se content increases. The delta self-consistent-field method is applied to correct band gaps that are underestimated by DFT. The band offsets clearly reflect the variation in valence band maxima and conduction band minima, thus providing information useful to the design of relevant quantum well structures. The positive formation enthalpies of both phases imply that CdS1-xSex is an immiscible system and tends to phase separate. The influence of lattice vibrations on the phase diagram is investigated by calculating the phonon density of states. Lattice vibration effects can reduce the critical temperature T-c and increase alloy solid solubilities. This influence is especially significant in the ZB structure. When only chemical interactions are present, the T-c values for WZ-and ZB-CdS1-xSex are 260K and 249 K, respectively. The lattice vibration enthalpy and entropy lower the T-c to 255K and 233 K, respectively.

  • 103.
    LUNDGREN, L
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    NORDBLAD, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    SVEDLINDH, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    BECKMAN, O
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    TOWARDS EQUILIBRIUM IN SPIN-GLASSES1985Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 57, s. 3371-3376Artikel i tidskrift (Refereegranskat)
  • 104.
    Lykissa, Iliana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Li, Shu-Yi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Ramzan, Muhammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Chakraborty, Sudip
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Granqvist, Claes Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Electronic density-of-states of amorphous vanadium pentoxide films: Electrochemical data and density functional theory calculations2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 18, s. 183701/1-/5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin films of V2O5 were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V2O5. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.

  • 105.
    Magnfalt, D.
    et al.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Nanoscale Engn Div, SE-58183 Linkoping, Sweden..
    Melander, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Boyd, R. D.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Plasma & Coatings Phys Div, SE-58183 Linkoping, Sweden..
    Kapaklis, Vassilios
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Sarakinos, K.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Nanoscale Engn Div, SE-58183 Linkoping, Sweden..
    Synthesis of tunable plasmonic metal-ceramic nanocomposite thin films by temporally modulated sputtered fluxes2017Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, nr 17, artikel-id 171918Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The scientific and technological interest for metal-dielectric nanocomposite thin films emanates from the excitation of localized surface plasmon resonances (LSPRs) on the metal component. The overall optical response of the nanocomposite is governed by the refractive index of the dielectric matrix and the properties of the metallic nanoparticles in terms of their bulk optical properties, size, and shape, and the inter-particle distance of separation. In order to tune the film morphology and optical properties, complex synthesis processes which include multiple steps-i. e., film deposition followed by post-deposition treatment by thermal or laser annealing-are commonly employed. In the present study, we demonstrate that the absorption resonances of Ag/AlOxNy nanocomposite films can be effectively tuned from green (similar to 2.4 eV) to violet (similar to 2.8 eV) using a single-step synthesis process that is based on modulating the arrival pattern of film forming species with sub-monolayer resolution, while keeping the amount of Ag in the films constant. Our data indicate that the optical response of the films is the result of LSPRs on isolated Ag nanoparticles that are seemingly shifted by dipolar interactions between neighboring particles. The synthesis strategy presented may be of relevance for enabling integration of plasmonic nanocomposite films on thermally sensitive substrates.

  • 106. Mikkelä, M. -H
    et al.
    Tchaplyguine, M.
    Urpelainen, S.
    Jänkälä, K.
    Björneholm, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Yt- och gränsskiktsvetenskap.
    Huttula, M.
    Photoelectron spectroscopy of unsupported bismuth clusters: size related effects of metallic properties2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, nr 8, s. 084326-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Evolution of metallic properties of free and initially neutral nanoscale Bi clusters has been studied using synchrotron radiation excited photoelectron spectroscopy. The 4f and 5d core as well as the valence levels have been probed. The cross-level analysis indicates metallic properties in Bi clusters in the observed size range from 0.5 nm to 1.4 nm. The behavior of the core-level and valence binding energies as a function of cluster size has been observed to be smooth and relatively consistent. Valence responses for the largest clusters have their shape and width similar to those of the polycrystalline solid Bi.

  • 107.
    Montero, José Amenedo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Guillen, C
    Department of Energy, CIEMAT, Madrid, Spain.
    Granqvist, Claes-Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Herrero, J
    Department of Energy, CIEMAT, Madrid, Spain.
    Niklasson, Gunnar A
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Lithium intercalation in sputter deposited antimony-doped tin oxide thin films: Evidence from electrochemical and optical measurements2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 15, s. 153702/1-/8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transparent conducting oxides are used as transparent electrical contacts in a variety of applications, including in electrochromic smart windows. In the present work, we performed a study of transparent conducting antimony-doped tin oxide (ATO) thin films by chronopotentiometry in a Li+-containing electrolyte. The open circuit potential vs. Li was used to investigate ATO band lineups, such as those of the Fermi level and the ionization potential, as well as the dependence of these lineups on the preparation conditions for ATO. Evidence was found for Li+ intercalation when a current pulse was set in a way so as to drive ions from the electrolyte into the ATO lattice. Galvanostatic intermittent titration was then applied to determine the lithium diffusion coefficient within the ATO lattice. The electrochemical density of states of the conducting oxide was studied by means of the transient voltage recorded during the chronopotentiometry experiments. These measurements were possible because, as Li+ intercalation took place, charge compensating electrons filled the lowest part of the conduction band in ATO. Furthermore, the charge insertion modified the optical properties of ATO according to the Drude model.

  • 108.
    Montero, José
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Ji, Yu-Xia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Granqvist, Claes G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Thermochromic light scattering from particulate VO2 layers2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, nr 8, artikel-id 085302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Particulate layers of thermochromic (TC) VO2 were made by reactive DC magnetron sputtering of vanadium onto In2O3: Sn-coated glass. The deposits were characterized by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Specular and diffuse optical transmittance and reflectance were recorded in the 300-2500-nm wavelength range and displayed pronounced TC effects. These properties could be reconciled with a semi-quantitative model based on Lorentz-Mie theory applied to the distribution of particle sizes and accounting for particle shapes by the Grenfell-Warren approach with equal-volume-to-area spheres.

  • 109.
    Moubah, Reda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Ahlberg, Martina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Zamani, Atieh
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Olsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Shi, S.
    Sun, Z.
    Carlson, S.
    Hallen, A.
    Hjörvarsson, Björgvin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Jönsson, Petra E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Origin of the anomalous temperature dependence of coercivity in soft ferromagnets2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 5, s. 053906-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the origin of the anomalous temperature dependence of coercivity observed in some soft ferromagnets by studying the magnetic and electronic properties of FeZr films doped using ion implantation by H, He, B, C, and N. The anomalous increase of the coercivity with temperature was observed only in the C- and B-doped samples. Using x-ray photoelectron spectroscopy, we show that the anomalous behavior of the coercivity coincides with the occurrence of an electron charge transfer for those implanted samples. The origin of the anomaly is discussed in terms of (i) magnetic softness, (ii) nature of the Fe-C and -B covalent bonds, and (iii) large charge transfer. (C) 2014 AIP Publishing LLC.

  • 110.
    Moubah, Reda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Magnus, Fridrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Hjörvarsson, Björgvin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Andersson, Gabriella
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Antisymmetric magnetoresistance in SmCo5 amorphous films with imprinted in-plane magnetic anisotropy2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 5, s. 053911-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on magnetoresistance measurements in SmCo5 amorphous films with a giant imprinted magnetic anisotropy. At low applied field parallel to the easy axis, the magnetoresistance exhibits a hysteretic, square, and antisymmetric shape. The antisymmetry in the magnetoresistance is a result of the non-uniform distribution of the magnetization direction over the sample in conjunction with the extraordinary Hall effect. Moreover, the combination of anisotropic magnetoresistance measurements and magnetic domain imaging demonstrates that the symmetry depends on the magnetization orientation with respect to the applied field.

  • 111.
    Moubah, Reda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Magnus, Fridrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Hjörvarsson, Björgvin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Andersson, Gabriella
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Strain enhanced magnetic anisotropy in SmCo/BaTiO3 multiferroic heterostructures2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 5, s. 053905-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the changes in magnetic properties of SmCo/BaTiO3 multiferroic heterostructures as the BaTiO3 substrate undergoes its structural phase transitions. The observations show that the macroscopic magnetization of the SmCo film is affected by the structural phase transitions of the BaTiO3 substrate. Kerr microscopy images show that the magnetic domains of SmCo films have a zigzag shape but their shape is not influenced by the strain transferred from the substrate during the structural phase transitions. Analysis of the magnetoelastic energy shows that the macroscopic change of the magnetization is accompanied by an enhancement of the magnetic anisotropy for the orthorhombic phase of the BaTiO3 substrate and not a change in symmetry of the anisotropy.

  • 112. Nagl, V
    et al.
    Hallén, Anders
    Masszi, Ferenc
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Evaluation of local lifetime in proton irradiated silicon1994Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550Artikel i tidskrift (Refereegranskat)
  • 113.
    Nayak, S.
    et al.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India..
    Dasari, K.
    Univ Puerto Rico, Dept Phys, San Juan, PR 00936 USA..
    Joshi, D. C.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India..
    Pramanik, P.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India..
    Palai, R.
    Univ Puerto Rico, Dept Phys, San Juan, PR 00936 USA..
    Waske, A.
    IFW Dresden, Inst Complex Mat, POB 270116, D-01171 Dresden, Germany..
    Chauhan, R. N.
    Natl Chiao Tung Univ, Dept Photon, Hsinchu 30010, Taiwan.;Natl Chiao Tung Univ, Display Inst, Hsinchu 30010, Taiwan..
    Tiwari, N.
    Natl Chiao Tung Univ, Dept Photon, Hsinchu 30010, Taiwan.;Natl Chiao Tung Univ, Display Inst, Hsinchu 30010, Taiwan..
    Sarkar, Tapati
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Thota, S.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India..
    Low-temperature anomalous magnetic behavior of Co2TiO4 and Co2SnO42016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, nr 16, artikel-id 163905Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the low-temperature anomalous magnetic behavior of ferrimagnetic spinels cobalt orthotitanate (Co2TiO4), which exhibits magnetic compensation behavior across 31.74 K, and cobalt orthostannate (Co2SnO4) exhibiting two sequential magnetic transitions, namely (i) ferrimagnetic to paramagnetic transition with Neel temperature T-N similar to 41 K and reentrant spin-glass behavior with glass transition temperature T-SG similar to 39 K. The Arrott plot (H/M versus M-2) criterion has been used to extricate the order of sequential magnetic transitions occurring below TN. Negative slopes of the Arrott plots below 32 K, metamagnetic-like character of the M-H isotherms, anomalies in the specific-heat (C-P T-1 versus T) below 15 K, and a zero-crossover of isothermal magnetic-entropychange (Delta S) signify the presence of pseudo first-order discontinuous magnetic phase transition in the low-temperature regime 5K <= T <= 32 K. The dc- and ac-susceptibilities of both Co2TiO4 and Co2SnO4 are interpreted in terms of frozen-spin-clusters, which are responsible for very large magnitudes of the coercivity H-C similar to 20 kOe and bipolar-exchange bias H-EB similar to -20 kOe observed below 10 K.

  • 114.
    Norde, Herman
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    A modified forward I-V plot for Schottky diodes with high series resistance1979Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 50, nr 7, s. 5072-Artikel i tidskrift (Refereegranskat)
  • 115.
    Olovsson, W.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Abrikosov, I.A.
    Variation of the effective exchange parameter across 3d-transition-metal series2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, nr 10, s. 10A317-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The so-called effective exchange parameter J0 of the classical Heisenberg Hamiltonian for magnetic interactions is investigated as a function of volume and occupation of the valence band across 3d-transition-metal series in face-centered-cubic (fcc) metals, from Mn to Ni. We show that there exists a particular area in the volume-electron concentration phase space, where the effective exchange parameter behaves anomalously. The peculiarity, in combination with deviations of the electronic structure in real alloys from the rigid-band behavior, should lead to highly frustrated magnetic configurations that were predicted theoretically for the fcc Invar alloys.

  • 116.
    Padam, R.
    et al.
    Indian Inst Technol Guwahati, Dept Phys, Gauhati 781039, India;Rajiv Gandhi Univ Knowledge Technol IIIT Basar, Dept Phys, Nirmal 504107, Telangana, India.
    Sarkar, Tapati
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Mathieu, Roland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Thota, S.
    Indian Inst Technol Guwahati, Dept Phys, Gauhati 781039, India.
    Pal, D.
    Indian Inst Technol Guwahati, Dept Phys, Gauhati 781039, India.
    Magnetic phase diagram of Co(Cr1-xAlx)2O-4 (x=0.0-1.0)2017Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 122, nr 7, artikel-id 073908Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the role of Al substitution in the magnetic properties of spinel CoCr2O4 by means of temperature dependent dc and ac magnetization and heat capacity measurements. Various compositions (0.0 <= x <= 1.0) of polycrystalline Co(Cr1-xAlx)(2)O-4 samples have been prepared by sol-gel processing and their crystal structure was investigated by X-ray diffraction which was found to crystallize in the normal cubic spinel structure. For x <= 0.1, the system exhibits multiple magnetic orderings (long range ferrimagnetic ordering T-C, spin-spiral ordering T-S, and lock-in transition T-L), similar to that of the parent compound, CoCr2O4. However, all the compositions between x = 0.1 and 0.5 exhibit long range ferrimagnetic ordering below T-C and also a short range order at low temperature. Spin-glass like ordering was noticed between x = 0.6 and 0.8 due to the diluted B-site occupancy, whereas the end compound CoAl2O4 (x = 1.0) shows antiferromagnetic behavior. On the basis of these results, we propose a magnetic phase diagram for the Co(Cr1-xAlx)(2)O-4 series as a function of the Al content (x) and measuring temperature (T).

  • 117. Pappas, S. D.
    et al.
    Kapaklis, Vassilios
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Delimitis, A.
    Jönsson, Petra E.
    Papaioannou, E. Th
    Poulopoulos, P.
    Fumagalli, P.
    Trachylis, D.
    Velgakis, M. J.
    Politis, C.
    Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, nr 5, s. 053918-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer (similar to 1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4750026]

  • 118. Parola, S.
    et al.
    Quesnel, E.
    Muffato, V.
    Xie, Ling
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Leifer, Klaus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Coignus, J.
    Slaoui, A.
    Optoelectronic properties of p-i-n heterojunctions based on germanium nanocrystals2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, nr 3, s. 033510-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the possibility of using physical vapour deposited Ge nanocrystals (NCs) in optoelectronic devices such as solar cells. We have prepared p-i-n heterojunctions based on p(+)-doped Si substrate/undoped Ge NCs/ZnO: Al layer stacks and their optoelectronic properties were characterised. Under light, the generation of photo-carriers from the Ge NCs themselves was demonstrated. The photovoltaic behaviour of the p-i-n structure was also highlighted, with a measured Voc of 224 mV compared to 580 mV in theory. The discrepancy between theory and experiment was discussed on the basis of TEM observations, optical and carrier generation measurements as well as modelling.

  • 119. Paul, Souvik
    et al.
    Kundu, Ashis
    Sanyal, Biplab
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Ghosh, Subhradip
    Anti-site disorder and improved functionality of Mn2NiX (X = Al, Ga, In, Sn) inverse Heusler alloys2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 13, s. 133903-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent first-principles calculations have predicted Mn2NiX (X = Al, Ga, In, Sn) alloys to be magnetic shape memory alloys. Moreover, experiments on Mn2NiGa and Mn2NiSn suggest that the alloys deviate from the perfect inverse Heusler arrangement and that there is chemical disorder at the sublattices with tetrahedral symmetry. In this work, we investigate the effects of such chemical disorder on phase stabilities and magnetic properties using first-principles electronic structure methods. We find that except Mn2NiAl, all other alloys show signatures of martensitic transformations in presence of anti-site disorder at the sublattices with tetrahedral symmetry. This improves the possibilities of realizing martensitic transformations at relatively low fields and the possibilities of obtaining significantly large inverse magneto-caloric effects, in comparison to perfect inverse Heusler arrangement of atoms. We analyze the origin of such improvements in functional properties by investigating electronic structures and magnetic exchange interactions.  

  • 120.
    Pehlivan, Esat
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Fractal Dimensions of Niobium Oxide Films Probed by Protons and Lithium Ions2006Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, nr 5, s. 053506-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclic voltammetry (CV) and atomic force microscopy (AFM) were used to determine fractal surface dimensions of sputter deposited niobium pentoxide films. Peak currents were determined by CV measurements. Power spectral densities obtained from AFM measurements of the films were used for calculating length scale dependent root mean square roughness. In order to compare the effect of Li and H ion intercalation at the fractal surfaces, LiClO4 based as well as propionic acid electrolytes were used. The CV measurements gave a fractal dimension of 2.36 when the films were intercalated by Li ions and 1.70 when the films were intercalated by protons. AFM measurements showed that the former value corresponds to the fractal surface roughness of the films, while the latter value is close to the dimensionality of the distribution of hillocks on the surface. We conclude that the protons are preferentially intercalated at such sites.

  • 121.
    Pehlivan, Ilknur Bayrak
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Marsal, Roser
    Georén, Peter
    Granqvist, Claes-Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Ionic relaxation in polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide polymer electrolytes2010Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, nr 7, s. 074102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymer electrolytes containing polyethyleneimine and different concentrations of lithium bis(trifluoromethylsulfonyl) imide were investigated by impedance spectroscopy at different temperatures. Two equivalent circuit models were compared for the bulk impedance response. The first one includes a conductive Havriliak-Negami (HN) element which represents ionic conductivity and ion pair relaxation in a single process, and the second model includes a dielectric HN element, which represents ion pair relaxation, in parallel with ion conductivity. Comparison of the two circuit models showed that the quality of the fit was similar and in some cases better for the conductive model. The experimental data follow the Barton-Nakajima-Namikawa relation, which relates the ion conductivity and the parameters of the relaxation. This indicates that ion conductivity and ion pair relaxation are two parts of the same process and should be described by the conductive model.

  • 122.
    Persson, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Berglund, M.
    Salehpour, Mehran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Improved optogalvanic detection with voltage biased Langmuir probes2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 24, s. 243301-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optogalvanic detectors show great potential for infrared spectroscopy, especially in cavity enhanced techniques where they, in contrast to ordinary absorption detectors, can perform intracavity measurements. This enables them to utilize the signal-to-noise ratio improvement gained from the extended effective path length inside an optical cavity, without losing signal strength due to the limited amount of light exiting through the rear mirror. However, if optogalvanic detectors are to become truly competitive, their intrinsic sensitivity and stability has to be improved. This, in turn, requires a better understanding of the mechanisms behind the generation of the optogalvanic signal. The study presented here focuses on an optogalvanic detector based on a miniaturized stripline split-ring resonator plasma source equipped with Langmuir probes for detecting the optogalvanic signal. In particular, the effect of applying a constant bias voltage to one of the probes is investigated, both with respect to the sensitivity and stability, and to the mechanism behind the generation of the signal. Experiments with different bias voltages at different pressures and gas composition have been conducted. In particular, two different gas compositions (pure CO2 and 0.25% CO2 in 99.75% N-2) at six different pressures (100 Pa to 600 Pa) have been studied. It has been shown that probe biasing effectively improves the performance of the detector, by increasing the amplitude of the signal linearly over one order of magnitude, and the stability by about 40% compared with previous studies. Furthermore, it has been shown that relatively straightforward plasma theory can be applied to interpret the mechanism behind the generation of the signal, although additional mechanisms, such as rovibrational excitation from electron-molecule collisions, become apparent in CO2 plasmas with electron energies in the 1-6 eV range. With the achieved performance improvement and the more solid theoretical framework presented here, stripline split-ring resonator optogalvanic detectors can evolve into a compact, inexpensive, and easy-to-operate alternative for future infrared spectrometers. (C) 2014 AIP Publishing LLC.

  • 123.
    Petersson, CS
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Andersson, R
    Baglin, J
    Dempsey, J
    Hammer, W
    d'Heurle, F
    Laplaca, S
    The thin film formation of rhodium silicides1980Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 51, s. 373-Artikel i tidskrift (Refereegranskat)
  • 124.
    Petersson, CS
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Baglin, J
    Dempsey, J
    d'Heurle, F
    La Placa, S
    Silicides of ruthenium and osmium: thin film reactions, diffusion, nucleation, stability1982Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 53, nr 7Artikel i tidskrift (Refereegranskat)
  • 125. Petersson, CS
    et al.
    Baglin, J
    Hammer, W
    d'Heurle, F
    Kuan, TS
    Ohdomari, I
    de Sousa Pires, Jorge
    Tove, PA
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Formation of iridium silicides from Ir thin films on Si substrates1979Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 50, nr 5, s. 3357-Artikel i tidskrift (Refereegranskat)
  • 126.
    Pettersson, Jonas
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Edoff, Marika
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Platzer-Björkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Electrical modeling of Cu(In,Ga)Se2 cells with ALD-Zn1xMgxO bufferlayers2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, nr 1, s. 014509-014509Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrical modeling of Cu(In,Ga)Se2 solar cells with Zn1-xMgxO buffer layers is performed. A number of  different  device  models  are  implemented  and  tested  by  comparing  simulation  results  and measurement data. Room temperature light-soaking and dark-light cross-over behavior as well aslow-temperature characteristics of these cells are studied. The light-soaking improvements in the solarcell  parameters  are  attributed  to  an  increase  in  buffer  donor  density,  due  to  persistent  photoconductivity, that counteracts charged acceptors in the absorber-buffer region. Dark-light JV-curvecross-over is explained by deep acceptor defects with small electron capture cross-section, in thebuffer. Best correspondence to measurements on ZnO and Zn0.83Mg0.17O cells is obtained with models including absorber-buffer interface acceptor states. No wideband-gap surface defect layer is needed to reproduce measurement data.

  • 127.
    Platzer Björkman, Charlotte
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Törndahl, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Abou-Ras, D.
    Malmström, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Kessler, John
    Stolt, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Zn(O,S) buffer layers by atomic layer deposition in Cu(In,Ga)Se-2 based thin film solar cells: Band alignment and sulfur gradient2006Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, nr 4, s. 044506-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin film solar cells with the structure soda lime glass/Mo/Cu(In,Ga)Se-2/Zn(O,S)/ZnO/ZnO:Al are studied for varying thickness and sulfur content of the Zn(O,S) buffer layer. These Zn(O,S) layers were deposited by atomic layer deposition (ALD) at 120 degrees C. Devices with no or small concentrations of sulfur in the buffer layer show low open-circuit voltages. This is explained by the cliff, or negative conduction-band offset (CBO), of -0.2 eV measured by photoelectron spectroscopy (PES) and optical methods for the Cu(In,Ga)Se-2 (CIGS)/ZnO interface. Devices with ZnS buffer layers exhibit very low photocurrent. This is expected from the large positive CBO (spike) of 1.2 eV measured for the CIGS/ZnS interface. For devices with Zn(O,S) buffer layers, two different deposition recipes were found to yield devices with efficiencies equal to or above reference devices in which standard CdS buffer layers were used; ultrathin Zn(O,S) layers with S/Zn ratios of 0.8-0.9, and Zn(O,S) layers of around 30 nm with average S/Zn ratios of 0.3. The sulfur concentration increases towards the CIGS interface as revealed by transmission electron microscopy and in vacuo PES measurements. The occurrence of this sulfur gradient in ALD-Zn(O,S) is explained by longer incubation time for ZnO growth compared to ZnS growth. For the Zn(O,S) film with high sulfur content, the CBO is large which causes blocking of the photocurrent unless the film is ultrathin. For the Zn(O,S) film with lower sulfur content, a CBO of 0.2 eV is obtained which is close to ideal, according to simulations. Efficiencies of up to 16.4% are obtained for devices with this buffer layer.

  • 128.
    Pochard, Isabelle
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material. Univ Bourgogne, CNRS, Lab Interdisciplinaire Carnot Bourgogne ICB, UMR 6303, Dijon, France.
    Frykstrand, Sara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Ahlström, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Forsgren, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Strømme, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Water and ion transport in ultra-adsorbing porous magnesium carbonate studied by dielectric spectroscopy2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 4, artikel-id 044306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Porous materials are used in application areas ranging from drug and vaccine delivery, medical implants, molecular sieves and cosmetics to catalysis and humidity control. In the present work, we employed an alternative approach to gain in-depth understanding about water interaction properties in such materials by the use of dielectric spectroscopy and thereby show that it is possible to obtain information that is not accessible from the more commonly employed water interaction analysis techniques. Specifically, the complex dielectric response of Upsalite, a novel, super-hydroscopic, high-surface area, porous magnesium carbonate material was measured in isothermal frequency scans between 10−3 and 106 Hz at controlled relative humidity (RH). We found the dielectric constant of the dry material to be 1.82. The ratio of bound to free water present in Upsalite after adsorption at room temperature was found to be high irrespective of the surrounding humidity with values ranging from ∼67% to ∼90%. We further found that OH ions are the charge carriers responsible for the electrode polarization observed in the dielectric response and that the amount of these ions that are free to move in the material corresponds to a concentration of the order of 1–10 μmol l−1 independent of RH. Finally, the OH diffusion coefficient displayed a drastic decrease with decreasing RH, typical of transport in unsaturated conditions. The presented results provide detailed insight about water interactions in the novel water adsorbing material under study and it is foreseen that the employed analysis methods can be used to evaluate other types of moisture adsorbing materials as well as the movement of functional species in the pores of inorganic drug delivery materials and materials tailored for adsorption of harmful charged species.

  • 129. Pohjonen, A. S.
    et al.
    Parviainen, S.
    Muranaka, Tomoko
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
    Djurabekova, F.
    Dislocation nucleation on a near surface void leading to surface protrusion growth under an external electric field2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, nr 3, s. 033519-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stress exerted on a conducting material surface by an external electric field can cause plastic deformation if the stress is concentrated somewhere in the material. Such concentration can occur due to the presence of a near surface void. The plastic deformation can lead to growth of a protrusion on the surface. To investigate the conditions where such a mechanism can operate, we employ concurrent electrodynamics-molecular dynamics simulations, analyze the distribution of stress near the void by using both the molecular dynamics and finite element method, and compare the result to the analytical expression for a void located deep in the bulk. By applying an electric field of exaggerated strength we are able to simulate the plastic deformation process within the timespan allowed by molecular dynamics simulations. In reality, longer timespans would allow for the initiation of the proposed mechanism at electric field strengths much lower than the values assumed for the simulations in the present work.

  • 130.
    Pramanik, P.
    et al.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India.
    Joshi, D. C.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India.
    Tiwari, N.
    Nanyang Technol Univ, Energy Res Inst, Singapore, Singapore.
    Sarkar, Tapati
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Pittala, S.
    Indian Inst Sci, Dept Phys, Bangalore 560012, Karnataka, India.
    Salman, O. O.
    IFW Dresden, Inst Complex Mat, Helmholtzstr 20, D-01069 Dresden, Germany.
    Manga, M-M
    Thota, S.
    Indian Inst Technol, Dept Phys, Gauhati 781039, Assam, India.
    Cationic distribution, exchange interactions, and relaxation dynamics in Zn-diluted MnCo2O4 nanostructures2019Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, nr 12, artikel-id 124302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report an experimental investigation of the electronic structure and magnetic properties of bulk and nanosized MnCo2O4 diluted with Zn. The cationic distribution for tetrahedral A-site dilution is (Co1-yA2+ZnyA2+)(A)[Mn3+Co3+](B)O-4 +/-delta, whereas B-site dilution results in (Co2+)(A)[Mn1-xB3+ZnxB2+Co3+](B)O4-delta. The strength of exchange interaction J(ij) between the magnetic ions in a bulk spinel lattice decreases by similar to 15% for A-site dilution relative to the undiluted compound; however, B-site dilution results in an enhancement in J(ij) by 17%. The frequency and temperature dependence of dynamic-susceptibility [chi(ac)(f, T)] studies of nanostructured compounds reveals the existence of spin-glass like behavior below the freezing temperature T-F similar to 125.7 K (for x(B) = 0.2) and 154.3 K (y(A) = 0.1). Relaxation time tau follows the Power-Law variation with a dynamical critical exponent zv = 6.17 and microscopic spin relaxation time tau(o) = 4.4 x 10(-15) s for x(B) = 0.2 (for y(A) = 0.1, zv = 5.2 and tau(o) = 5.4 x 10(-13) s). The amplitude and peak position in chi(ac)(T) decreases with an increase in the DC bias field, which indicates that the spin-glass phase can survive in the presence of low fields forming a critical line with an exponent 2/3. This behavior is similar to the de Almeida-Thouless (AT-line) analysis in the T-H phase diagram which supports the existence of spin-glass like behavior below T-F in these Zn diluted spinels. 

  • 131.
    Raanaei, Hossein
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialfysik.
    Nguyen, Hugo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Andersson, Gabriella
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialfysik.
    Lidbaum, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Experimentell fysik.
    Korelis, Panagiotis
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialfysik.
    Leifer, Klaus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Experimentell fysik.
    Hjörvarsson, Björgvin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialfysik.
    Imprinting layer specific magnetic anisotropies in amorphous multilayers2009Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, nr 2, s. 023918-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate how layer specific in-plane magnetic anisotropy can be imprinted in amorphous multilayers. The anisotropy is obtained by growing the magnetic layers in the presence of an external field and the anisotropy direction can thereby be arbitrarily chosen for each of the magnetic layers. We used Co68Fe24Zr8 and Al70Zr30 layers as building blocks for demonstrating this effect. The imprinting is expected to be obtainable for a wide range of amorphous materials when grown at temperatures below the magnetic ordering temperature.

  • 132.
    Ramzan, M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Ahuja, R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides2009Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, nr 1, s. 016104-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Light weight complex metal hydrides, sodium hydride (NaH), and lithium hydride (LiH) are the last step materials during hydrogen release process of alanates and borates, which are promising candidates for hydrogen storage. We report ab initio molecular dynamics (MD) calculations based on density functional theory to study the hydrogen-deuterium exchange in NaH and LiH. We predict the single hydrogen-deuterium exchange in NaH and LiH and calculate the self-diffusion constants, << D >>(NaH)approximate to 1.46x10(-9) m(2) s(-1) of deuterium in NaH at 420 K and << D >>(LiH)approximate to 1.49x10(-9) m(2) s(-1) of deuterium in LiH at 550 K, which are in good agreement with the experimental values.

  • 133.
    Ramzan, Muhammad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden.
    Ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides2009Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, nr 016104Artikel i tidskrift (Refereegranskat)
  • 134.
    Ramzan, Muhammad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Lebegue, Sebastien
    Laboratorie de Cristallographie, Résonance Magnétique et Modélisations, Institut Jean Barriol, Nancy Université.
    Larsson, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Structural, magnetic, and energetic properties of Na2FePO4F, Li2FePO4F, NaFePO4F, and LiFePO4F from ab initio calculations2009Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, nr 4, s. 043510-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we report on Na2FePO4F and Li2FePO4F, which are materials that are used as cathodes in batteries, using density functional theory with the LDA, LDA + U, GGA, or GGA + U approximations. Specifically, we study their crystal structure, electronic structure, and magnetic properties and provide similar information about the intermediate compounds LiFePO4F and NaFePO4F. Finally, the intercalation voltages of the corresponding batteries are calculated using various exchange-correlation approximations and conclusions are drawn about which one is the most suitable to use for the study of this class of materials.

  • 135.
    Ramzan, Muhammad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Luo, Wei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    High pressure, mechanical, and optical properties of ZrW2O82011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, nr 3, s. 033510-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present the high pressure studies of well known negative thermal expansion material ZrW2O8 on the basis of our density functional theory calculations. We reproduce the experimental alpha and gamma crystal structures of ZrW2O8. We calculate the transition pressure (from alpha to gamma) of this material to be approximate to 26 kbar. Our calculated positional and axial parameters are in an excellent agreement with the available experimental values for the both alpha and gamma phases of this material. Then we study the mechanical properties of this material. We calculate the elastic constants, bulk, shear and Young's moduli, Poisson's ratio, and Debye temperature of alpha-ZrW2O8. In our study, we find that the generalized gradient approximation method fails to obtain the correct values while the local density approximation (LDA) method successfully reproduces the experimental bulk modulus of ZrW2O8. Our calculated values of the shear and Young's moduli, Poisson's ratio, and Debye temperature of alpha-ZrW2O8 with LDA method are also in good agreement with the experimental results. Finally, we predict and analyze the optical properties of this material.

  • 136.
    Reichel, L.
    et al.
    IFW Dresden.
    Giannopoulos, G.
    Demokritos National Center of Scientific Research, Athens.
    Kauffmann-Weiss, S.
    IFW Dresden .
    Hoffmann, M.
    IFW Dresden .
    Pohl, D.
    IFW Dresden.
    Edström, Alexander
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Oswald, S.
    IFW Dresden .
    Niarchos, D.
    Demokritos National Center of Scientific Research, Athens.
    Rusz, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Schultz, L.
    IFW Dresden .
    Fähler, S.
    IFW Dresden .
    Increased magnetocrystalline anisotropy in epitaxial Fe-Co-C thin films with spontaneous strain2014Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 21, s. 213901-Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Rare earth free alloys are in focus of permanent magnet research since the accessibility of the elements needed for nowadays conventional magnets is limited. Tetragonally strained iron-cobalt (Fe-Co) has attracted large interest as promising candidate due to theoretical calculations. In experiments, however, the applied strain quickly relaxes with increasing film thickness and hampers stabilization of a strong magnetocrys- talline anisotropy. In our study we show that already 2 at% of carbon substantially reduce the lattice relaxation leading to the formation of a spontaneously strained phase with 3% tetragonal distortion. In these strained (Fe0.4Co0.6)0.98C0.02 films, a magnetocrystalline anisotropy above 0.4 MJ/m3 is observed while the large polarization of 2.1 T is maintained. Compared to binary Fe-Co this is a remarkable improve- ment of the intrinsic magnetic properties. In this paper, we relate our experimental work to theoretical studies of strained Fe-Co-C and find a very good agreement.

  • 137.
    Richter, J. H.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Karlsson, P. G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Sandell, A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Electronic structure of a laterally graded ZrO2-TiO2 film on Si(100) prepared by metal-organic chemical vapor deposition in ultrahigh vacuum2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Journal of Applied Physics, Vol. 103, nr 9, s. 094109-094109-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A TiO2-ZrO2 film with laterally graded stoichiometry has been prepared by metal-organic chemical vapor deposition in ultrahigh vacuum. The film was characterized in situ using synchrotron radiation photoelectron spectroscopy (PES) and x-ray absorption spectroscopy. PES depth profiling clearly shows that Ti ions segregate toward the surface region when mixed with ZrO2. The binding energy of the ZrO2 electronic levels is constant with respect to the local vacuum level. The binding energy of the TiO2 electronic levels is aligned to the Fermi level down to a Ti/Zr ratio of about 0.5. At a Ti/Zr ratio between 0.1 and 0.5, the TiO2 related electronic levels become aligned to the local vacuum level. The addition of small amounts of TiO2 to ZrO2 results in a ZrO2 band alignment relative to the Fermi level that is less asymmetric than for pure ZrO2. The band edge positions shift by -0.6 eV for a Ti/Zr ratio of 0.03. This is explained in terms of an increase in the work function when adding TiO2, an effect that becomes emphasized by Ti surface segregation.

  • 138.
    Richter, Jan Hinnerk
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Karlsson, Patrik G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Sanyal, Biplab
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Blomquist, J.
    Uvdal, P.
    Sandell, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Band alignment at the ZrO2/Si(100) interface studied by photoelectron and x-ray absorption spectroscopy2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 10, s. 104120-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present measurements of the Zr and Si core level photoelectron binding energies relative to the Fermi level and the vacuum level under a ZrO2 growth series on Si(100). It is shown that the Zr core level binding energy is most properly referenced to the local vacuum level already from the monolayer regime. This confirms the insulating properties of ZrO2. The Si core levels are referenced to the Fermi level and undergo shifts consistent with the disappearance of the mid-band-gap states originating from the (2×1) reconstruction on the clean Si(100) surface. The use of O 1s x-ray absorption spectroscopy (XAS) to determine the location of the conduction band edge of ZrO2 is discussed with the aid of ab initio calculations. It is demonstrated that the conduction band edge is located at the XAS peak position and that the position relative to the valence band can be determined by aligning the O 1s XAS spectrum to the O 1s photoelectron spectrum. The study thus establishes that photoelectron spectroscopy in conjunction with x-ray absorption spectroscopy forms a most powerful tool for studies of the band alignment at metal oxide-silicon interfaces.

  • 139. Rosling, M
    et al.
    Bleichner, H
    Jonsson, P
    Nordlander, E
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    The ambipolar diffusion coefficient in silicon: Dependence on excess-carrier concentration and temperature1994Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 76, nr 5, s. 2855-2859Artikel i tidskrift (Refereegranskat)
  • 140.
    Rowan-Robinson, Richard M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, England.
    Hindmarch, A. T.
    Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, England.
    Atkinson, D.
    Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, England.
    Efficient current-induced magnetization reversal by spin-orbit torque in Pt/Co/Pt2018Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 124, nr 18, artikel-id 183901Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Current-induced magnetization reversal due to spin-orbit torque is demonstrated in an anisotropy controlled Pt/Co/Pt trilayer. The samples were designed to have weak perpendicular magnetic anisotropy, with a measured anisotropy field of (1340 +/- 20) Oe. Reversal is shown to be dominated by a damping-like torque associated with the spin-Hall effect. A small in-plane magnetic field was required to break the symmetry and enable reversal. With a 273 Oe field, magnetization reversal occurred with a current density amplitude of only 5 x 10(10) Am-2, which is shown to be consistent with a simple model. The field-like torque is negligible, so measurements indicate that the imaginary part of the spin-mixing conductance associated with Co/Pt interfaces must be negligible.

  • 141.
    Rudisch, Katharina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Davydova, Alexandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Platzer Björkman, Charlotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Scragg, Jonathan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    The effect of stoichiometry on Cu-Zn ordering kinetics in Cu2ZnSnS4 thin film2018Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, nr 16, artikel-id 161558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu-Zn disorder in Cu2ZnSnS4 (CZTS) may be responsible for the large open circuit voltage deficit in CZTS based solar cells. In this study, it was investigated how composition-dependent defect complexes influence the order-disorder transition. A combinatorial CZTS thin film sample was produced with a cation composition gradient across the sample area. The graded sample was exposed to various temperature treatments and the degree of order was analyzed with resonant Raman spectroscopy for various compositions ranging from E- and A-type to B-, F-, and C-type CZTS. We observe that the composition has no influence on the critical temperature of the order-disorder transition, but strongly affects the activation energy. Reduced activation energy is achieved with compositions with Cu/Sn > 2 or Cu/Sn < 1.8 suggesting an acceleration of the cation ordering in the presence of vacancies or interstitials. This is rationalized with reference to the effect of point defects on exchange mechanisms. The implications for reducing disorder in CZTS thin films are discussed in light of the new findings.

  • 142.
    SANDLUND, L
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    SVEDLINDH, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    GRANBERG, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    NORDBLAD, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    LUNDGREN, L
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    EXPERIMENTAL-EVIDENCE FOR THE EXISTENCE OF AN OVERLAP LENGTH IN SPIN-GLASSES1988Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 64, s. 5616-5618Artikel i tidskrift (Refereegranskat)
  • 143.
    Sanyal, Biplab
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Volume dependent magnetism in zinc-blende MnX (X=N,P,As,Sb,Bi) compounds2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 7, s. 07D704-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Half-metallic ferromagnets are promising candidates for use in spintronic devices. In order to investigate the complex magnetism of such systems, we have studied the magnetic interactions in zinc-blende MnX (X=N,P,As,Bi,Sb) systems as a function of volume by ab initio density functional calculations. The calculated Heisenberg pair-exchange parameters show a strong volume dependence resulting in the transition from a metallic to a half-metallic behavior for certain systems. As a result, in MnAs, the calculated Curie temperatures, obtained from Monte Carlo simulations using ab initio exchange parameters and a classical Heisenberg Hamiltonian, increase with an increase in volume. Calculations of self-consistent noncollinear spin configurations indicate that spins deviate strongly from collinear ordering for low volumes whereas they align in a collinear ferromagnetic fashion for high volumes.

  • 144.
    Sanyal, Biplab
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Grånäs, Oscar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Knut, Ronny
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Coleman, V. A
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Thunström, Patrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Iusan, Diana M
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Karis, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Westin, Gunnar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Electronic structure of Co doped ZnO: Theory and experiment2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 7, s. 07D130-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied the electronic structure of Co doped ZnO by theory and experiment. Photoelectron and x-ray absorption spectroscopy experiments were performed on 5% Co doped ZnO thin films. The results show that Co-3d states lie in the valence band and hybridize considerably with O-2p states. These results compare qualitatively with our density functional calculations combined with a Hubbard approach to include strong electron correlations within the Co-3d state.

  • 145.
    Sanyal, Biplab
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Knut, Ronny
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Grånäs, Oscar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Iusan, Diana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Karis, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Inhomogeneity in Co Doped ZnO Diluted Magnetic Semiconductor2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 7, s. 07D131-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Here, we have studied the chemical and magnetic interactions in Co doped ZnO diluted magnetic semiconductor by ab initio density functional calculations. The calculated chemical pair interaction parameters suggest a strong tendency of clustering between Co atoms. Both chemical and magnetic pair interaction parameters are short ranged with a large first neighbor interaction. Monte Carlo simulations show that the Curie temperature for a homogeneous sample is low, whereas allowing for an inhomogeneous growth results in very high Curie temperatures. It is argued that these inhomogeneities may be the reason for the observation of high Curie temperatures in Co doped ZnO. It is also demonstrated that the electronic structure is modified significantly in presence of Co clusters.

  • 146. Saxegaard, Magne
    et al.
    Yang, DeZheng
    Wahlström, Erik
    Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway.
    Brucas, Rimantas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Hanson, Maj
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.
    Field and current-induced magnetization reversal studied through spatially resolved point-contacts2010Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, nr 10, s. 103909-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ABSTRACT: We present results from scanning tunneling microscopy based point-contact measurements of the local resistance in octagon shaped, Co (20 nm )/ Cu (5 nm )/ Fe <sub>19</sub> Ni <sub>81</sub>(2.5 nm ) spin-valve rings. Through this technique one can detect the magnetoresistance with spatial resolution, and link it to magnetic domain wall motion within the ring. Measurements with varying currents indicate current-induced effects leading to offsets in the magnetic fields required for magnetic switching. The offsets can be attributed to current-induced spin-transfer torque effects for the thin Fe <sub>19</sub> Ni <sub>81</sub> layer and to Oersted field effects for the thick Co layer.

    Full-text · Article · Jun 2010 · Journal of Applied Physics

  • 147.
    Saygin, Hasan
    et al.
    Istanbul Technical University, Nuclear Energy Institute.
    Sisman, Altug
    Istanbul Technical University, Nuclear Energy Institute.
    Quantum Degeneracy Effect on the Work Output from A Stirling Cycle2001Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, nr 6, s. 3086-3089Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of quantum degeneracy on the work output from a Stirling cycle working at quantum degeneracy conditions (QDCs) is analyzed. Expressions for net work outputs of Stirling power cycles working with monatomic ideal Bose and Fermi gases are derived by using the quantum ideal gas equation of state. Ratios of net work outputs of Stirling cycles working with Bose and Fermi gases to the net work output of a classical Stirling cycle (RBW and RWF, respectively) are obtained. Variations of RBW and RFW with TH are examined for a given temperature ratio (τ=TL/TH) and a specific volume ratio (rν=νH/νL). At QDC, it is seen that RBW has a maximum value, which is greater than unity. On the other hand, there is no maximum or minimum point for RFW and RFW⩽1 for any values of TH. Consequently, the use of Bose gas as a working fluid in a Stirling cycle provides an advantage since it causes the net work output per cycle to increase by consuming more heat energy. This fact is seen to be in the opposite direction for a Stirling cycle working with Fermi gas.

  • 148. Schattschneider, P.
    et al.
    Rubino, S.
    Stoeger-Pollach, M.
    Hebert, C.
    Rusz, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Calmels, L.
    Snoeck, E.
    Energy loss magnetic chiral dichroism: A new technique for the study of magnetic properties in the electron microscope (invited)2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 7, s. 07D931-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The similarity between x-ray absorption near edge structure and electron energy loss near edge structure is well known. However, "exporting" x-ray magnetic circular dichroism (XMCD) to the transmission electron microscope (TEM) was considered impossible with present technology since electron probes possessing chirality (i.e., spin polarization) cannot be set up with sufficient intensity. But recently magnetically induced chiral electronic transitions were detected in the TEM. In analogy to XMCD we introduced the term EMCD (energy loss magnetic chiral dichroism). The mechanism builds upon the formal equivalence between the mixed dynamic form factor for inelastic electron scattering and the absorption cross section for x-rays. Experiments on the 3d ferromagnets show effects very similar to XMCD. Calculations based on the WIEN2K package are in good agreement with experiments. The recent improvement in signal strength and spatial resolution allows now to study atom specific spin and orbital moments on a scale of less than 10 nm, an important progress for spintronics and nanomagnetism.

  • 149.
    Schmitt, Thorsten
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik II.
    Augustsson, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Duda, Laurent-C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Nordgren, Joseph
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik II.
    Höwing, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Gustafsson, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Li-insertion into V6O13 battery cathodes studied by soft X-ray spectroscopies2004Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 95, s. 6444-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Changes in the electronic structure of V6O13 on lithium-ion insertion into battery cathodes were studied by soft x-ray absorption (SXA) spectroscopy and resonant soft x-ray emission (SXE) spectroscopy. SXA and resonant SXE spectra were recorded ex situ for cycled battery cathodes discharged to different potentials corresponding closely to distinct lithiated stages (LixV6O13,x=0,1,…,6). Large systematic changes were observed in the vanadium and oxygen x-ray spectra, reflecting the effects of electrochemical reduction associated with the Li-ion insertion. Spectral shape analysis indicates that a large fraction of the vanadium ions have been reduced to V3+ ions for the highest degree of lithiation,x=6. Nevertheless, further lithiation may be possible, in view of the linear development of the vanadium and oxygen bands on charge uptake.

  • 150.
    Schmitt, Thorsten
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik II.
    Augustsson, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Duda, Laurent-C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Nordgren, Joseph
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik II.
    Höwing, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Gustafsson, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Li-insertion into V6O13 battery cathodes studied by soft X-ray spectroscopies2004Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 95, s. 6444-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Changes in the electronic structure of V6O13 on lithium-ion insertion into battery cathodes were studied by soft x-ray absorption (SXA) spectroscopy and resonant soft x-ray emission (SXE) spectroscopy. SXA and resonant SXE spectra were recorded ex situ for cycled battery cathodes discharged to different potentials corresponding closely to distinct lithiated stages (LixV6O13,x=0,1,…,6). Large systematic changes were observed in the vanadium and oxygen x-ray spectra, reflecting the effects of electrochemical reduction associated with the Li-ion insertion. Spectral shape analysis indicates that a large fraction of the vanadium ions have been reduced to V3+ ions for the highest degree of lithiation,x=6. Nevertheless, further lithiation may be possible, in view of the linear development of the vanadium and oxygen bands on charge uptake. 

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