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Optical reflectance/transmittance and magneto-optical Kerr effect of Fe/Cr superlattices (SL) are studied by using the first principles full-potential linearized augmented plane-wave method. Equilibrium atomic structures are optimized through total energy and atomic force approaches. Pronounced peaks in the ellipticity and optical spectra are obtained around 3000 cm −1 for the ferromagnetic SL due to the inter-band electron excitations. The change in magnetic ordering from ferromagnetic to antiferromagnetic cases alters optical functions, namely, the reflectance, R and transmittance T . The calculated Δ R / R and Δ T / T have a pronounced maximum around 2000 cm −1 and decay almost linearly thereafter toward high photon energies, a result that agrees qualitatively well with experiment.

The nonlinear susceptibilities, χ (2) , for second-harmonic generation at the (111) surfaces of silicon and diamond are studied in the framework of the self-consistent tight-binding theory. The electron-electron and electron-ion Coulomb interactions are treated by solving the secular equation self-consistently with respect to the orbital occupancies. The influence of hydrogen adsorption on the χ (2) spectra of the silicon and diamond surfaces is investigated. Intense response of χ (2) is found in the spectral regions corresponding to surface-bulk and bulk-bulk type optical transitions. The results obtained are discussed in comparison with data available from the literature.

We investigated atomic geometry, surface band structure, and differential optical reflectance spectra of the (001) surface of diamond within the semiempirical tight binding theory. The total energy minimization method has been used to determine the equilibrium geometry of the diamond (001) surface. The results show that the (001) surface of diamond relaxes to a (2 × 1) symmetric dimer atomic configuration. Its electronic structure is characterized by the pronounced surface states in the gap. Optical transitions between the surface states on the (001)-(2 × 1) surface of diamond cause an enormous reflectivity in the range near 2.6 eV which reveals strong polarization anisotropy.

The electroreflectance spectra of cubic silicon carbide crystals are measured in the range 1.0 to 5.6 eV. The energies of direct optical transitions are determined using a multiple oscillator model. The electronic band structure and optical functions of 3C-SiC crystals are calculated by semiempirical pseudopotential methods. From comparison between theoretical and experimental optical spectra numerical parameters of electronic band structure 3C-SiC are obtained, and values of atomic form factors of carbon atoms, giving the realistic band structure and optical spectra of 3C-SiC, are determined.

Experimental data were found to be in qualitative agreement with theoretical calculations of the degree of linear polarization. The effect of the pumping level on the shape of photoluminescence spectra of superlattices with various types of bands was established. The electron-phonon coupling constants of type-II superlattices were evaluated.

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A model of the electronic structure of graphite-like carbon films, describing the semiconductor properties of this material, is presented. Spectra of optical constants of microcrystalline carbon films in the region λ = 0.4–8.0 μm were studied by the spectral ellipsometry and IR reflection methods. A number of distinctive features of the spectra, associated with both the appearance of CC- and CH n -type bonds and direct energy gaps, were found. Analysis of the optical data using the proposed model makes possible a common interpretation of our results and literature data. Values of a parameter Θ, which is an averaged qualitative parameter of structural distortions within carbon microcrystallites as compared with crystalline graphite, are determined from comparison of theoretical results and experimental data.

High temperature superconducting films of GdBa2Cu3O7−x have been studied by spectral ellipsometry and X-ray spectroscopy. Spectra of the imaginary part of the dielectric permittivity function, ϵ2, have been obtained in the range from 1.5 to 4.5 eV. The structural parameters, charge carrier density and stoichiometry (with respect to oxygen) of the films have been measured.

Reflected second harmonic spectra from a Si(OO1)-(2x 1) surface in ultrahigh vacuum change in radically different ways upon adsorption of hydrogen, germanium, or boron. Ab initio and semi-empirical tight-binding microscopic theories reproduce and explain the observed trends.

The first data are presented on the change (following implantation) in the refractive index and the band structure of silicon on sapphire films. The implantation was effected with phosphor ions of 40 keV and doses from 1012 to 1016 cm−2. An increase following implantation of the refractive index and the energy of the first direct allowed transitions E1 is noted, indicating changes in the second coordination sphere. The profile E1(x) is studied pointing to heterogenization effects. The films were annealed with ruby laser pulses of 0.2 J/cm2. The same laser was used to study the lux dependence of the injection level Δn and surface photo-emf VΦ. Hysteresis in the VΦ(Δn) dependence (after the use of maximum intensity of the laser beam) is noted indicating irreversible straightening of the bands at the film surface.

The optical absorption α and electroreflectance (ER) of amorphous silicon (a-Si) foils free from a substrate were measured. IR vibrational spectra showed that the a-Si foils, which contained no more than 0.5% H2, can be described as containing inhomogeneous regions of solutions of oxygen, nitrogen and hydrogen in silicon. The average size of these regions is about 0.1 μm. Comparison of IR and ER data show that a-Si foils are characterized by greater ordering of nearest atomic shells than that in hydrogenated a-Si.

Electroreflectance spectra for thin silicon films have been investigated in the photon energy region 2.8–5.0 eV. The critical point energy E 1 ( E′' 0 ) and the broadening parameter Γ were determined for unexposed and ion-bombarded surfaces. Definite correlation between Γ -1 and the Hall mobility was found. It is concluded that the variations in E 1 ( E '0 ) for the films are caused by the emergence of density “tails” and the existence of inward mechanical microtensions.

It has been shown that band parameters for unimplanted films differ from those for bulk materials. Mechanical stresses and increased concentrations of defects seem to be responsible for this difference. The neighbourhood of the surface and the existence of drain paths for bulk defects determine the activity of the surface as a collector for mobile defects and hence their accumulation and their subsequent combination and annihilation reactions. From this point of view ion-implanted films with radiation-induced defects exhibit specific types of behaviour. For example, low energy ion bombardment (together with the removal of a very thin surface layer by etching) leads to an extensive movement of defects towards the surface and to a purification of the corresponding layer. In a number of cases even structural phase transformations take place within the surface layer, which lead in particular to the creation of surface excitons. High energy ion bombardment does not alter the band parameters of the films at the depth d of ion penetration but distorts the structure at the surface owing to a drain of defects into this layer. At the same time centres of scattering and radiative recombination are effectively induced at the depth d.