Heat capacity of LiInS2, LiInSe2 and LiInTe2 between 200 and 550 K

The molar heat capacity at constant pressure of LiInS₂, LiInSe₂ and LiInTe₂ was measured in the temperature range from about 200 K to 550 K. An analysis of the experimental data showed that the anharmonic contribution to the heat capacity can be described by a polynomial of fourth order in the temperature. A comparison of the results for the LiInC₂^VI compounds with those for the AgB^IIIC₂^VI and A^IIB^IVC₂^V chalcopyrite compounds showed that the lattice anharmonicity effects are essentially influenced by the specific nature of the Li C^VI bond.     

Force constant scaling and interatomic potential in tetrahedral semiconductors

The force constants of tetrahedral semiconductors derived from lattice vibration data are analysed in terms of a generalized Morse potential and of a potential with power laws of the interatomic distance for the repulsive and attractive term. It is found that the Morse potential is an appropriate model for describing the dependence of the force constants on the bond length in the elemental, A^IIIB^V, A^IIB^VI and A^IB^IIIC semiconductors.     

Lattice Vibrations and Interatomic Forces in AIIB2IIIC4VI Defect-Chalcopyrite Compounds (I) Keating Model Considerations

The lattice vibrations of the A^IIB^III₂C^VI₄ semiconductors with defect-chalcopyrite structure are treated in a simplified version of the Keating model considering only interaction with nearest neighbours and assuming that all anions occupy their ideal lattice sites. It is found that in this model the frequencies of the nonpolar and polar modes with highest energy are determined by the properties of the B^III–C^VI sublattice alone. The frequencies of all the other optical modes depend not only on the A^II–C^VI and B^III–C^VI interactions but are also influenced by the presence of the ordered array of vacancies. The results obtained are compared with previous model considerations.     

Elastic debye temperature of compounds with sphalerite structure

Elastic Debye temperatures θ_EL of the semiconducting compounds A^IIIB^V, A^IIB^VI and CuCl are evaluated from second order elastic constants C_ik available from the literature. The dependence of θ_EL on temperature is given. The results at 0 K are compared with those calculated from low temperature measurements of specific heat. Generally, the agreement between these values is better than found in the literature up to now.     

Thermal Expansion Coefficient of Binary Semiconductors

The linear thermal expansion coefficient of tetrahedrally coordinated A^IIB^VIand A^IIIB^Vsemiconductors has been calculated using plasmon energy data. A simple relation between the bond length and plasm on energy has been derived. The calculated values of thermal expansion coefficient and bond length have been compared with the experimental values and the values reported by differentworkers. An excellent experiment has been obtained between them.     

Über die röntgenographische Analyse der mittleren quadratischen Atomverschiebungen in einigen Halbleiterkristallen

X-ray measurements of the Debye-Waller factor were performed with single crystals of Ge and of semiconducting compounds A^IIIB^V, A^IIB^VI, A^IVB^VI in the temperature range 100 K — 1000 K. From the results the mean square atomic displacements 〈u²〉 and the Debye characteristic temperatures θ of the materials were calculated. Both parameters are discussed with respect to the influence of the temperature, the influence of point defects and, in the case of the compounds, deviations from the stoichiometric composition on the thermal lattice vibrations. Finally, considerations are presented, concerning the relationship between the parameters 〈u²〉 and θ_M, respectively, and the activation energies of vacancy formation and diffusion in the materials.     

Lattice Vibrations and Interatomic Forces in AIIB2IIIC4VI Defect-Chalcopyrite Compounds (II). Analysis of Nonpolar Optical Modes

A simplified version of the Keating model originally derived for defect-chalcopyrite compounds is extended to include all A^IIB₂^IIIC₄^VI compounds with ordered arrays of vacancies. It is shown that the trends and frequencies of the nonpolar optical modes of these compounds can be described within this model. Simple scaling laws for the interatomic force constants are proposed and compared with corresponding relations for other binary and ternary compounds with tetrahedral coordination.     

High-frequency dielectric constant of AIIB2IIIC4VI ordered-vacancy compounds

The mean high-frequency dielectric constant of ZnIn₂Se₄, CdIn₂Se₄, ZnIn₂Te₄ and CdIn₂ Te₄ was determined from unpolarized infrared reflectivity spectra measured in the wavenumber range v̄ = 600 – 4000 cm⁻¹. A simple relation based on the quantum dielectric theory for multibond crystals is proposed to estimate the mean high-frequency dielectric constant of the A^IIB₂^IIIC₄^VI compounds from individual bond susceptibilities. The results of the calculations are compared with existing experimental data, and susceptibilities of the Hg C^VI bonds are estimated.     

Comparative infrared lattice vibration study of LiGaO2 and LiInO2 (II). Interatomic force constants

The frequencies of the wurtzite-like modes due to Li–O and Ga–O bond vibrations in LiGaO₂ and of the rocksalt-like mode due to Li–O bond vibrations in LiInO₂ are determined from the infrared reflectivity spectra of the compounds. The force constants for the Li–O and Ga–O bonds in LiGaO₂ follow the same trends as those found for the A^IB^IIIC₂^VI chalcogenides with tetrahedral cordination. The results for LiInO₂ are compared with measurements on the octahedrally coordinated modification of LiAlO₂.     

Chemical Bond in AIIBV2 Systems from Magnetic Susceptibility Data

Some peculiarites of chemical bond in A^IIB^V₂ systems from the data on the magnetic susceptibility of the A^IIB^V₂ compounds and their solid solutions are discussed. With this aim in view the magnetic susceptibility has been divided into the Langevin diamagnetic and van Vleck paramagnetic terms. The diamagnetic susceptibility of valence electrons, affecting the chemical bond in a crystal against the covalency parameter along the A – B, A – A, B –B bonds in A^IIB^V₂ compounds, has been analysed. The covalency parameter of the A^IIB^V₂ compounds has been evaluated. Closeness of the covalency parameter values for monoclinic β-ZnP₂ and tetragonal CdP₂, CdAs₂, is evidently, one of the reasons for the solid solution formation between the above mentioned compounds.     

Infrared and Raman Spectra of ZnIn2Se4

Infrared reflectivity and Raman spectra of polycrystalline ZnIn₂Se₄ revealed a total number of seven structures due to optical vibrational modes. Based on a comparison with previous measurements on other A^IIB₂^IIIC₄^VI compounds a symmetry assignment of the modes is proposed.     

Trends in the thermal expansion coefficients of the AIBIIIC2VI and AIIBIVC2V chalcopyrite compounds

Empirical relations are derived for the average linear thermal expansion coefficient α_L and the linear thermal expansion coefficients α_a and α_c of the lattice parameters a and c, respectively, of the A^IB^IIIC₂^IV and A^IIB^IVC₂^V compounds. It is shown that the thermal expansion coefficients of all tetrahedrally coordinated compounds can be described within the same model. The anisotropy of the thermal expansion coefficients depends essentially on the lattice constant ratio c/a. There exists a critical c/a value below of which α_c becomes negative.     

Vacancy formation enthalpies in AIBIIIC chalcopyrite semiconductors

Formation enthalpies ΔH_v of single vacancies in all A^IB^IIIC₂^VI chalcopyrite structure compounds are estimated using the macroscopic cavity model. A comparison with atomic sublimation enthalpies ΔH_sub of the B^III and C^VI atoms derived from existing partial vapour pressure data shows that within the accuracy of this data and the theoretical calculations the relation ΔH_v ⪆ ΔH_sub is fulfilled as expected from general considerations.     

Thermal expansion anisotropy and individual bond expansion coefficients in ternary chalcopyrite compounds

The individual bond expansion coefficients of the A^IIB^IVC and A^IB^IIIC₂^VI chalcopyrite compounds are calculated from the principal linear thermal expansion coefficients of the lattice parameters using the regular B C tetrahedron model and a model with a temperature independent free parameter of the lattice. It is shown that the bond expansion coefficients derived from the latter model are in better agreement with the trends found for the interatomic forces in the chalcopyrite compounds and observed for the thermal expansion coefficients in the binary AC, A^IIC and BC compounds.     

Influence of intrinsic defects on the electrical properties of AIBIIIC compounds

The electrical parameters of undoped melt grown A^IB^IIIC^VI₂ crystals are compared with predictions which can made considering the deviations from stoichiometry due to the incongruent evaporation of these compounds. It is shown that the electrical properties of all A^IB^IIIC compounds can be interpreted in a consistent manner if the electrical activity (donor or acceptor) of the intrinsic defects is considered in the covalent bonding model.     

Polaritätsabhängige Struktureffekte in tetraedrisch koordinierten Halbleitern

On the basis of the semiempirical dielectric theory of structure a sensitive parameter accounting for the relative stability of the zincblende and the wurtzite structure in epitaxial layers of A_IIB_VI-compounds on (111)-orientated A_IIIB_V, Si, and Ge substrates is introduced. The statements of the proposed theoretical model are in good agreement with the experimental results.     

Ionicity of the chemical bond in AIBIIIC semiconductors

The Phillips — van Vechten dielectric theory for binary tetrahedral compounds and Levine's extension of this theory to multibond crystals is used to evaluate the bond ionicities in the A^IB^IIIC chalcopyrite compounds with A^I = Cu, Ag from spectroscopic data. In deriving the ionicity of the A^I—C^VI bond the influence of the noble metal d electrons it taken into account. The results obtained are compared with previous estimations.     

Calculations of homogeneous region in Ga1−xAlxAs and GaAs1−xPx ternary solid solutions

Ternary solid solutions of A^IIIB^V compounds are considered as pseudobinary A(x)^IIIB(x)^v compounds, where the behaviour of A(x)^III and B(x)^v pseudoatoms is quite similar to A^III and B^v atoms in a binary A^IIIB^v crystal. Weak dependence of point defect contribution into Gibb's energy of A^IIIB^v crystal on its defect nature, random character of ternary solid solutions of A^IIIB^v compounds allow to use already for binary compounds developed formalism in the determination of component thermodynamic potentials of solid solution. Basing on literature data for the equilibrium solidus of AlAs the approximation for the temperature dependence of thermodynamic potential of an AB quasimolecule in A^IIIB^v crystal is revised. This result together with the well-known parameters for the equilibrium liquidus in Ga–P, Ga–As, and Al–As systems were used for calculations of the nonstoichiometric factor at the boundary of a homogeneous region in Ga_1−xAl_xAs and GaAs_1−xP_x ternary solid solutions. The results are compared with the known literature data.     

Trends in the microhardness of the CuBIIIC chalcopyrite compounds

On the basis of a microhardness scaling law found for the A^IIB^IVC compounds and of the dependence of the microhardness on conductivity type and composition observed experimentally in CuInSe₂ a model is proposed to describe the trends in the microhardness of the CuB^IIIC compounds. The results are compared with experimental data and other microhardness estimates. It is found that most of the existing microhardness measurements can be interpreted within the model.     

Über die Vorausbestimmung der thermoelastischen Eigenschaften von Halbleiter-Verbindungen

Extending some results of thermoelastic behavior of uniquely bonded crystal groups with constant Grüneisen-number γ to the field of strongly homologous intermetallic compounds (e. g. semiconductors, A^IIIB^V), it seems possible to predict the thermoelastic properties of those compounds, which are of unstable or otherwise non-investigable consistence.