| 1. |
- Hamberg, Ivar, et al.
(författare)
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Band-gap widening in heavily Sn-daped In203
- 1984
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 30:6, s. 3240-3249
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Tidskriftsartikel (refereegranskat)abstract
- Films of pure and Sn-doped semiconducting Inz03 were prepared by reactive e-beam evaporation. The spectral absorption coefficient was evaluated by spectrophotometry in the (2—6)-eV range. The extracted band gap increases with electron density (ne ) approximately as ne 2/3 for ne ≤10-21 cm-3 . This result is interpreted within an effective-mass model for n-doped semiconductors well above the Mott critical density. Because of the high degree of doping, the impurities are ionized and the associated electrons occupy the bottom of the conduction band in the form of an electron gas. The model accounts for a Burstein-Moss shift as well as electron-electron and electron-impurity scattering treated in the random-phase approximation. Experiments and theory were reconciled by assuming a parabolic valence band with an effective mass -0.6m. Earlier work on doped oxide semiconductors are assessed in the light of the present results.
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| 2. |
- KARLSSON, Ulf O, et al.
(författare)
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SURFACE ELECTRONIC-STRUCTURE OF MG(0001)
- 1982
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 26:4, s. 1852-1858
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Neve, Jesper, et al.
(författare)
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Electron band structure, resistivity, and the electron-phonon interaction for niobium under pressure
- 1983
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 28:2, s. 629-637
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Tidskriftsartikel (refereegranskat)abstract
- Accurate measurements of the electrical resistance of Nb are presented as a function of temperature and pressure in the region 0-40°C and 0-1 GPa. From these measurements and published results for the compressibility and the pressure dependence of the superconducting transition temperature Tc we evaluate the pressure dependence of the electron-gas plasma frequency ω(p). The electronic structure of Nb is calculated from a self-consistent linear muffin-tin orbital method and results are obtained for the pressure dependence of the density of states at the Fermi surface, the root mean square over the Fermi surface of the Fermi velocity, the optical mass, and the plasma frequency. The experimental and calculated results for the pressure dependence of ω(p) are both close to dlnω2 / dlnV=-1.9. This agreement suggests that measurements of the electrical resistance as a function of temperature and pressure provide a new test of band-structure calculations. From our measurements of the resistance and calculations of ω(p) and from published results for the compressibility we obtain the pressure dependence of the electron-phonon interaction λ(p). With p given in gigapascals, the result is dlnλ / dp=-0.0047.
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| 4. |
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| 5. |
- Paul, Jan, et al.
(författare)
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Electronic structure of CO adsorbed on a Cu(111) surface analyzed with molecular cluster models
- 1982
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 26:8, s. 4073-4077
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Tidskriftsartikel (refereegranskat)abstract
- Using the self-consistent Hartree-Fock-Slater model we have calculated the electronic structure for various Cux(CO)y clusters symbolizing not only CO bound to "on-top" and "bridge" sites but also some lateral CO-CO interaction on a Cu(111) surface. By comparison with experimental photoemission data we are able to reproduce the observed energies of the occupied CO 4σ, 1π, and 5σ orbitals as well as the partly occupied 2π orbital. In our model we assume CO to be adsorbed on "top" sites for coverages less than ⊖=0.33 [(sqrt[3]×sqrt[3])R30°] and on both top and bridge sites for ⊖>0.33. The experimentally observed peak of intensity at the Fermi edge which increases with coverage above 0.33 is in our model explained by the occupation of CO orbitals of the b1 and b2 symmetry types, i.e., "π" orbitals, degenerate for top positions (C3v), split by the change to bridge positions (C2v). Our results further indicate that the broadened 5σ-1π intensity peak at high coverages is a result of CO bound to top and bridge sites.
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| 6. |
- Slack, Glen A., et al.
(författare)
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Pressure and temperature effects on the thermal conductivity of CuCl
- 1982
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 26:4, s. 1873-1884
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity of polycrystalline, cubic CuCl has been measured from 100 to 480 K and pressures from 0.5 to 2.7 GPa by a transient hot-wire technique. The heat transport is produced by phonons. The absolute value of the conductivity is low and becomes nearly temperature independent at high temperatures where it is approaching the minimum possible value. The conductivity decreases with increasing pressure; its volume derivative, g, is negative over the whole range studied. This effect is related to the negative Grüneisen parameters, γ, for the transverse-acoustic phonons. Some specific-heat-capacity values were also measured.
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