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We investigated the effects of the incorporation of both Na and O on defect structures for p-type Cu-poor CuInS2thin films on the basis of the analysis of experimental data using photoluminescence and the secondary ion mass spectrometry and theoretical results obtained by ab-initioelectronic band structure calculations. We propose a model of the defect structure for CuInS2codoped with Na and O. The NaCuand OSform a complex in which they occupy nearest-neighbor sites. The above complex plays an important role in the annihilation of the deep level due to the n-type divacancy which includes Cu vacancies (VCu) and vacancies of the sulfur close to the VCusite.

We have investigated the electronic structures of n- or p-type doped ZnO based on ab initioelectronic band structure calculations. We find unipolarityin ZnO; n-type doping using Al, Ga or In species decreases the Madelung energy while p-type doping using N species increases the Madelung energy, in addition to causing substantial localization of the N states. Codoping using reactive codopants, Al, Ga or In, enhances the incorporation of N acceptors in p-type codoped ZnO. We find the delocalized states of N for p-type ZnO codoped with N and Al (Ga).

Current-voltage measurements were performed on Ba1-xKxBiO3/Nb-doped SrTiO3(BKBO/STO:Nb) all-oxide-type Schottky junctions in the temperature range of 30 to 300 K. The relative permittivity ?r(E, T) of undoped SrTiO3(110) was measured as a function of both temperature and electric field. An anomalous increase in ideality factor n(T) and decrease in zero-bias barrier height ?b0(T) with decreasing temperature were observed and were analyzed using the interfacial layer model with a thin insulating interfacial layer present between metal contact (BKBO) and semiconductor interface (STO:Nb). The increase in n(T) at low temperature can be explained by taking into account the temperature dependence of the permittivity of the depletion layer (STO:Nb). The effect of the electric field dependence of the permittivity of STO:Nb on n(T) is also discussed using an approximate electric field dependence, ?r(T, E)=b/(a+E2)1/2, where aand bare constants.

We have studied the electronic structures of CuIn(S0.875X0.125)2(X=O, N, P, C, Si or B) based on the ab-initioelectronic band structure calculations using the augmented spherical wave (ASW) method. For p-type CuInS2crystals doped with N, P, C, Si or B, compared with the case of undoped CuInS2, we have found a smaller energy difference between the center of gravity of 3dbands of Cu close to dopants and that of the outermost pbands of ligands of the Cu atoms. We have clarified the mechanism of dependence of the hybridization between Cu 3dstates and the outermost pstates of dopants, X, on the Cu to X bond character (ionic or covalent).

The physical parameters of a Ba1-xKxBiO3(BKBO) superconductor have been successfully estimated by measuring the Hall effect and optical reflectivity spectra for epitaxial thin films. The results of these measurements at room temperature indicated that the optimized BKBO thin film has a carrier density of 5.0×1021cm-3and an effective mass of 0.9m0. Supposing the free-electron model, Fermi energy of BKBO could be estimated to be 1.2 eV . Using these parameters, the quasi-particle transmission probability was also calculated for the BKBO/Nb-doped SrTiO3junction.

The broadening of the gap edge in the conductance-voltage ( dI/ dV-V) characteristics for native-barrier Ba1-xKxBiO3-gold (BKBO//Au) and MgO-barrier Ba1-xKxBiO3-gold (BKBO/MgO/Au) junctions was investigated by using a gap-energy distribution model where the inhomogeneity of the energy gap ? at the junction interface was taken into consideration. It was demonstrated that the broadening of the dI/ dV-Vcurves and their temperature dependence (T<2TC/3) in both junctions could be explained by assuming the Gaussian distribution of gap energies (at T=0 K) with ?0(0)=3.1 meV, ??=0.9 meV for the BKBO//Au junction and ?0(0)=3.5 meV, ??=1.1 meV for the BKBO/MgO/Au junction, where ?0(0) and ?? represent the center point and the width of the distribution, respectively. It was found that the value ?? could be regarded as a criterion for the quality of the tunneling junction.

We have studied the influence of intrinsic defects, cation vacancies (VCu, VIn) and anti-site defects (InCu, CuIn), on the bandstructure of nonstoichiometric CuInS2based upon the ab-initioelectronic band-structure calculations using the augmented spherical wave (ASW) method. We have found that an energy shift of the center of gravity of S 3pband is a key parameter for controlling change in the type of conductivity. In p-type crystals (VCu, CuIn, and VIn), we have clarified an increase in the strength of the interaction between Cu 3dstates and S 3pstates caused by a weight shift of the S 3pband towards higher energies in contrast to that in n-type (InCu).

The electrical properties of Ba1-xKxBiO3/Nb-doped SrTiO3all-oxide-type Schottky junctions have been investigated by measuring their current-voltage and capacitance-voltage (C-V) characteristics at room temperature. The relative permittivity ?rof Nb-doped SrTiO3could be approximated as ?r(E)=b/? a+E2, where Eis the electric field, aand bare constants. Taking into account the field dependent permittivity and interfacial layer, we carried out a quantitative analysis of the potential barrier and 1/C2-Vcharacteristics. The non-linear 1/C2-Vcharacteristics could be quantitatively explained by considering the field dependent permittivity and the bias dependence of the barrier height due to the presence of the interfacial layer.