| 1. |
- da Silva, AF, et al.
(författare)
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Impurity resistivity of the double-donor system Si : P,Bi
- 1999
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 60:23, s. 15824-15828
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Tidskriftsartikel (refereegranskat)abstract
- The electrical resistivity of the shallow double-donor system Si:P,Bi, prepared by ion implantation, was investigated in the temperature range from 1.7 to 300 K. Good agreement was obtained between the measured resistivities and resistivities calculated by a generalized Drude approach for the same temperatures and dopant concentrations. The critical impurity concentration for the metal-nonmetal transition for the double-doped Si:P,Bi system was found to lie between the critical concentrations of the two single-doped systems, Si:P and Si:Bi. [S0163-1829(99)11747-8].
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| 2. |
- Aboelfotoh, M. O., et al.
(författare)
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Schottky-barrier behavior of metals on n- and p-type 6H-SiC
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:7, s. 075312-
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Tidskriftsartikel (refereegranskat)abstract
- The Schottky-barrier height of a number of metals (Ti, Ni, Cu, and Au) on n- and p-type Si-terminated 6H-SiC has been measured in the temperature range 150-500 K. It is found that the barrier height to n-type 6H-SiC does not exhibit a temperature dependence, while for p-type 6H-SiC the change in the barrier height with temperature follows very closely the change in the indirect energy gap in 6H-SiC. These results are inconsistent with models of Schottky-barrier formation based on the concept of a charge neutrality level. Furthermore, the present results cannot be reconciled with a defect pinning mechanism, contrary to the conclusions of earlier studies on III-V compound semiconductors. We suggest that chemical bonding at the metal-semiconductor interface plays an important role in determining the Schottky-barrier height.
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| 3. |
- Abrashev, M. V., et al.
(författare)
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Raman spectroscopy of CaMnO(3) : Mode assignment and relationship between Raman line intensities and structural distortions
- 2002
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 65:18, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Polarized Raman spectra of oriented finely twinned CaMnO(3) thin films and nonpolarized Raman spectra of CaMnO(3) ceramics were studied at room temperature using several excitation laser wavelengths. The selection rules for the polarized Raman spectra, obtained from samples consisting of finely twinned orthorhombic domains, were calculated and the symmetry of all observed Raman lines was determined. The relationship between the intensity of the Raman lines and the distortions in the ABO(3) perovskites with GdFeO(3)-type structure is discussed. These distortions can be described as superposition of four simple basic distortions: two MnO(6) octahedral tilts, Jahn-Teller deformation of Mn(3+) O(6) octahedra, and shift of the A ions from their sites in the ideal perovskite. Twenty of the 24 Raman-allowed modes in the real GdFeO(3)-type structure have counterparts in only one of the four simpler structures, obtained by a single basic distortion. The assignment of the Raman lines of CaMnO(3) to definite atomic vibrations, most of them activated by a single basic distortion, was made in close comparison with the results of lattice dynamical calculations and the Raman spectra of isostructural LaMnO(3) and CaGeO(3).
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| 4. |
- Abrikosov, IA, et al.
(författare)
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Applicability of the coherent-potential approximation in the theory of random alloys
- 1998
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 57:22, s. 14164-14173
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The applicability of the coherent-potential approximation (CPA) for the description of electronic properties of completely random alloys is investigated. This is done by calculating the density of states and the total energy for different systems and by c
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| 5. |
- Abrikosov, IA, et al.
(författare)
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Locally self-consistent Green's function approach to the electronic structure problem
- 1997
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 56:15, s. 9319-9334
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The locally self-consistent Green's function (LSGF) method is an order-N method for calculation of the electronic structure of systems with an arbitrary distribution of atoms of different kinds on an underlying crystal lattice. For each atom Dyson's equat
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| 6. |
- Abrikosov, IA, et al.
(författare)
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Magnetically induced crystal structure and phase stability in Fe1-cCoc
- 1996
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 54:5, s. 3380-3384
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We present an ab initio determination of the crystallographic phase stability of Fe-Co alloys as a function of concentration, using the coherent potential approximation. A bcc --> hcp phase transition is found at a concentration of 85 at.% of Co, in good
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| 7. |
- ABRIKOSOV, IA, et al.
(författare)
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THEORETICAL ASPECTS OF THE FECNI1-C INVAR ALLOY
- 1995
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 51:2, s. 1058-1063
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Agui, A, et al.
(författare)
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Bulk and interface Al 2p core excitons in GaAs/AlAs/GaAs heterostructures
- 1999
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 59:16, s. 10792-10795
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Aluminum 2p soft-x-ray emission and absorption spectra (XES and XAS) of a GaAs/AIAs/GaAs heterostructure semiconductor have been measured with high-energy resolution. The Al 2p XES shows a similar feature to that of AlxGa1-xAs alloys. Strong Al 2p core ex
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| 9. |
- Ahlberg, Martina, et al.
(författare)
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Effect of ferromagnetic proximity on critical behavior
- 2012
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 85:22, s. 224425-1-224425-6
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the magnetic phase transition in amorphous Fe93Zr7(x angstrom)/Co95Zr5(1 angstrom) multilayers, where x = 25, 50, and 75. The extremely thin CoZr layer induces magnetic order at temperatures well above the inherent ordering temperature of Fe93Zr7. The changes in the critical exponent beta, associated with the temperature dependence of the magnetization, imply a crossover from two-to three-dimensional behavior as the FeZr thickness is reduced, consistent with a substantial magnetic induction in the FeZr layers. In addition we determined the exponents delta and gamma, of the critical isotherm and the susceptibility, respectively, and their values confirm the nonuniversal character of the phase transition. Scaling of the results yields an excellent data collapse and is found to hold in the crossover regime where the universality hypothesis is not applicable.
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| 10. |
- Ahuja, R, et al.
(författare)
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Electronic and optical properties of red HgI2
- 1996
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 54:15, s. 10419-10424
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Within the local-density approximation we have used the linear muffin-tin orbital method, without geometrical approximations, to calculate the electronic structure of red HgI2. Using the self-consistent potential we have calculated the energy bands and fr
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| 11. |
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| 12. |
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| 13. |
- Ahuja, R, et al.
(författare)
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Optical properties of graphite from first-principles calculations
- 1997
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 55:8, s. 4999-5005
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We present theoretical results for the frequency-dependent dielectric response, both for the electric field parallel and perpendicular to the c axis of graphite. The calculations are performed using a full-potential linear muffin-tin orbital method. Our c
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| 14. |
- Ahuja, R, et al.
(författare)
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Theoretical and experimental study of the graphite 1s x-ray absorption edges
- 1996
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 54:20, s. 14396-14404
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Theoretical calculations in combination with experiments for the pi* and sigma* x-ray absorption edges are reported for graphite. Theory and experiment agree well for the leading pi* and sigma* resonances. By comparing theoretical calculations for a singl
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| 15. |
- Ahuja, R, et al.
(författare)
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Theoretical confirmation of the high-pressure orthorhombic phase in strontium
- 1998
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 58:13, s. 8152-8154
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The recent experimental observation of a new phase (Sr III) at high pressure in strontium metal, with a base-centered orthorhombic crystal structure, is investigated theoretically by means of a full-potential linear muffin-tin-orbital method. Our calculat
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| 16. |
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| 17. |
- Ahuja, R, et al.
(författare)
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Theoretical high-pressure studies of Cs metal - art. no. 014102
- 2001
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Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 6301:1, s. 4102-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the crystal structures of cesium metal under high compressions by means of first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital (FPLMTO) method
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| 18. |
- Ahuja, R, et al.
(författare)
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Theoretical high-pressure studies of silicon VI
- 1999
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 60:21, s. 14475-14477
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We have investigated Si theoretically under high compressions by means of first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method. Our results confirm the
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| 19. |
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| 20. |
- Ahuja, R, et al.
(författare)
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Theoretical prediction of a phase transition in gold - art. no. 212101
- 2001
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Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 6321:21, s. 2101-
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Tidskriftsartikel (refereegranskat)abstract
- We performed theoretical investigations on gold under high pressure through first principles self-consistent total-energy calculations within the local-density approximation as well as generalized gradient approximation using full-potential muffin-tin-orb
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| 21. |
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| 22. |
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| 23. |
- Akahama, Yuichi, et al.
(författare)
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Structural stability and equation of state of simple-hexagonal phosphorus to 280 GPa : Phase transition at 262 GPa
- 2000
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Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 61:5, s. 3139-3142
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Tidskriftsartikel (refereegranskat)abstract
- A structural phase transition and the equation of state of the simple-hexagonal (sh) phase, P-V, of phosphorus were investigated at pressures up to 280 GPa using monochromatic synchrotron x-ray diffraction. The P-V phase, which was stable above 137 GPa, has shown a structural transition to a higher-pressure phase, P-VI, above 262 GPa, while the c/a ratio of the sh phase slightly increased with increasing pressure from 0.948 to 0.956. The structure of the P-VI phase has been proposed to be bcc. The bulk modulus (B0) and the atomic volume at atmospheric pressure (V0) of the sh phase were estimated to be 84.1 GPa and 14.2 Å3, with a fixed value of the pressure derivative of the bulk modulus (B′0).
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| 24. |
- Akerman, J. J., et al.
(författare)
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Dislocation-mediated creep of highly separated vortices in a-axis-oriented HgBa2CaCu2O6+delta thin films
- 2001
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 64:2
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Tidskriftsartikel (refereegranskat)abstract
- Using ac susceptibility, we determine the critical current density J(c) and the flux creep activation energy U of an a-axis-oriented HgBa2CaCu2O6+delta thin film. The critical current density at helium temperatures is found to be 4.6 x 10(4) A/cm(2), i.e., about two orders of magnitude smaller than for corresponding films with c-axis orientation. The temperature and ac field dependent activation energy is consistent with dislocation-mediated flux creep and well described by U(T,H-ac)=U-o(1-t(4))H-ac(-1/2) with t=T/T-c, T-c=120K, and U-o = 0.77 eV Oe(1/2) for temperatures T>45 K and in the field range studied. The activation energy is of the same order as that found in c-axis-oriented films. Below T = 45 K the activation energy is observed to decrease as thermally assisted quantum creep becomes increasingly important.
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| 25. |
- Akerman, J. J., et al.
(författare)
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Two-stage crossover from thermal to quantum flux creep of dilute vortex ensembles in various high-T-c superconducting thin films
- 2001
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 64:9
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Tidskriftsartikel (refereegranskat)abstract
- The thermal-to-quantum flux creep crossover at low vortex densities has been studied in YBa2Cu3O7, TlBa2CaCu2O7-delta, and HgBa2CaCu2O6+delta thin films using ac susceptibility. The crossover temperatures T-cr are 10-11, 17, and 30 K, respectively. Both thermal and quantum flux creep is suppressed as the vortex density is decreased. We observe a two-stage nature in the crossover behavior which appears to be a general property of all the three materials studied.
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