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The phase composition and optical properties of hydrogenated amorphous films of silicon suboxide ( a-SiO:H) with silicon nanoclusters are studied. Ultrasoft X-ray emission spectroscopy show that silicon- suboxide films with various oxidation states and various amorphous silicon-cluster contents can be grown using dc discharge modulation. In films with an ncl-Si content of ∼50%, the optical-absorption edge is observed, whose extrapolation yields an optical band gap estimate of ∼3.2-3.3 eV. In the visible region, rather intense photoluminescence bands are observed, whose peak positions indicate the formation of silicon nanoclusters 2.5-4.7 nm in size in these films, depending on the film composition. [ABSTRACT FROM AUTHOR]

A possible explanation is suggested for discrepancies between experimental values obtained by different authors for the barrier height at the same metal-semiconductor junction. It is supposed that the problem is caused primarily by the structural inhomogeneity of the metal. As a result, the junction behaves as an assembly of a large number of subjunctions connected in parallel. To determine the effect of metal inhomogeneity on the properties of a junction, the dependence of the barrier height in a Schottky diode on the junction area is investigated under the assumption that, with an increase in the area of a junction between a singlecrystal semiconductor and a polycrystalline metal, the degree of inhomogeneity and, thus, the number of subjunctions, increases. [ABSTRACT FROM AUTHOR]

The results of the study of donor U-centers of tin and germanium in lead chalcogenides by Mössbauer emission spectroscopy are discussed. The published data regarding the identification of amphoteric U-centers of tin in glassy binary arsenic and germanium chalcogenides using Mössbauer emission spectroscopy, and in multicomponent chalcogenide glasses using Mössbauer absorption spectroscopy are considered. Published data concerning the identification of two-atom U-centers of copper in lattices of semimetal copper oxides by Mössbauer emission spectroscopy are analyzed. The published data on the detection of spatial inhomogeneity of the Bose-Einstein condensate in superconducting semiconductors and semimetal compounds, and on the existence of the correlation between the electron density in lattice sites and the superconducting transition temperature are presented. The principal possibility of using Mössbauer U-centers as a tool for studying the Bose-Einstein condensation of electron pairs during the superconducting phase transition in semiconductors and semimetals is considered. [ABSTRACT FROM AUTHOR]

The results of a complex investigation into dark-current relaxation in the long-time region of an MIM structure based on an As-Se thin-film chalcogenide system are presented. The values of parameters describing the electronic processes ocurring in the contact layers of the investigated compounds are estimated. The coincidence of the nature of conductivity and charge-accumulation mechanisms is revealed. The relaxation-time distribution function is calculated, and its structural sensitivity to such technological factors as the change in the composition stoichiometry and the method for manufacturing experimental samples is established. [ABSTRACT FROM AUTHOR]

Single-crystal samples of cationic clathrates in the Sn-In-As-I system with different indium contents have been synthesized. Their crystal structure has been analyzed and their thermoelectric properties have been measured. These compounds are found to be n-type semiconductors with high absolute values of the Seebeck coefficient ( S = 400-600 μV/K) and anomalously low thermal conductivity (κ ≤ 0.4 W/(m/K) at 300 K, which is characteristic of amorphous materials. The reasons for the anomalously low thermal conductivity of these semiconductors are discussed and ways for optimizing their thermoelectric properties are shown. [ABSTRACT FROM AUTHOR]

Temperature dependences of photoconductivity of layered and conventional undoped films of amorphous hydrogenated silicon have been studied within a wide range of temperatures (130-420 K) and illumination intensities (0.1-60 mW cm). It is established that a higher photosensitivity of layered films compared with conventional films is governed by a low dark conductivity of layered films as a consequence of a deeper position of the equilibrium Fermi level in the band gap and the absence of temperature quenching of photoconductivity in these films. It is shown that these specific features of electrical and photoelectric properties of layered films can be attributed to a low concentration of silicon dangling bonds in comparison with the concentration of oxygen-related acceptor centers, which feature a larger capture coefficient for holes. [ABSTRACT FROM AUTHOR]

A method of constructing a fractal model of noncrystalline solid substance is considered using the example of amorphous silicon. In systems of iteration functions, the physical meaning of dihedral and valence angles of the elementary crystallographic cell is assigned to arguments. The model adequacy is estimated by the radial distribution function, the atomic structure density, the distribution of valence and dihedral angles, and the density of dangling interatomic bonds. [ABSTRACT FROM AUTHOR]

The structural systematic features of quantum-yield variation in charge-carrier photogeneration are investigated for polymer systems with molecules into which polymethine dyes of various structures had been introduced. The correlations between the quantum yields and the second-harmonic-generation efficiency in the media containing such dyes are revealed, and relations of the quantum yields to such dye-molecule structural parameters as the ionization potential of its donor fragment, the electron affinity of its acceptor fragment, and the electron-transfer distance between donor and acceptor fragments of the dye molecule are established. [ABSTRACT FROM AUTHOR]

The effect of singlet oxygen on the formation of nanoporous silicon in the case of photoelectrochemical etching of p-Si is studied. Pulsed electrolysis was used to discriminate between chemical and electrochemical processes. The pulsed etching of silicon was accompanied by pulsed illumination coinciding either with current pulses or with zero-current periods. An analysis of the results obtained demonstrated that, as the number of silicon nanocrystals increases under illumination, singlet oxygen starts to be generated from molecular oxygen dissolved in the electrolyte. This process leads to oxidation of the surface of silicon nanocrystallites and to a change in its passivation. [ABSTRACT FROM AUTHOR]

The temperature and concentration dependences of resistivity and thermopower in a heavily doped and highly compensated semiconductor alloy ZrNiSn1− x In x in the temperature range T = 80–380 K at x = 0.005–0.15 are studied. It is assumed that the ZrNiSn semiconductor doped heavily with the In acceptor impurity is an amorphous semiconductor. It is experimentally established that there is a proportionality between the parameters of fluctuations in the bands of continuous energies, depth of fluctuations, and the depth of the potential well for a small-scale fluctuation. The conclusion advanced by Shklovskiĭ and Éfros in 1972 [10] is experimentally confirmed for the first time; this conclusion is concerned with the assertion that, in a highly doped and completely compensated semiconductor, the maximum amplitude of fluctuations in the bands of continuous energies is equal to the half width of the band gap of the semiconductor, while the Fermi level is located near the midgap. [ABSTRACT FROM AUTHOR]

The in situ X-ray photoelectron spectroscopy observation of low-temperature recrystallization of an amorphous Ge layer deposited on a ZnSe film at room temperature is reported. It is shown that the experimentally measured shifts of the Ge 3 d core level are consistent with the changes observed in the crystal structure of the layer by the high-energy electron diffraction technique in the reflection mode of measurements. The shifts can be attributed to successive nanometer-scaled structural changes in the Ge layer with increasing temperature. [ABSTRACT FROM AUTHOR]

In previous studies, we obtained an expression for the time dependence of the transient current in amorphous semiconductors during dispersive transport. The expression contains a stable density with a characteristic exponent equal to the dispersion parameter α < 1; excess carrier concentrations are expressed in terms of fractional stable densities with the characteristic exponent α. In this study, generalized equations of diffusion and carrier drift in unordered semiconductors for dispersive transport were derived. A main feature of these equations is the fractional-order partial time derivative. Solutions to these equations are expressed in terms of fractional stable densities. At α → 1, fractional stable distributions become normal, and generalized equations become ordinary diffusion and drift equations. Thus, the fractional differential approach allows the description of normal and dispersive transport within a unified mathematical model. [ABSTRACT FROM AUTHOR]

The method of molecular dynamics is applied to the study of variations in the physical properties of vitreous and amorphous silicon nanoparticles when heated from 300 to 1700 K. The nanoparticles consist of 300, 400, and 500 atoms. The energy and the average length of the Si-Si bond are calculated, and the average number of bonds per atom is determined. Thermally induced strains tend to change the distribution of the excess potential energy among the concentric layers in the nanoparticles. It is shown that, energetically, the most preferential layer is the middle spherical layer of the “warm” nanoparticle. The temperature behavior of the radial and tangential components of the atomic mobility coefficient in the concentric layers is considered. It is established that there is a liquid layer at the nanoparticle surface in the vicinity of the transition to melting. The vitrified Sin nanoparticles are kinetically more stable than the similar-sized amorphous particles. [ABSTRACT FROM AUTHOR]

Electrical properties of thin SmS polycrystalline films with various values of the lattice constant at T = 300–580 K are studied. Specific features of the temperature dependences of electrical conductivity at T > 450 K are revealed. The effect of generation of the electromotive force with magnitude as large as 1.3 V at T = 440–470 K is observed when the films were subjected to the pressure of a spherical indenter. It is shown that it is possible to transform SmS films into a high-resistivity state (with the difference in the resistivity by three orders of magnitude) by applying an electric field with the strength higher than 100 V/cm. All the results obtained are accounted for using a model of the phenomenon of the electromotive-force generation in SmS under uniform heating of the sample and can also be attributed to the variable valence of samarium ions with respect to the lattice defects. [ABSTRACT FROM AUTHOR]

The grain microstructure of polycrystalline structures formed in thin amorphous Ge–Te, Tl–Se, and Cd–Te condensates has been studied using transmission electron microscopy. Pronounced internal lattice bending (up to 200 deg/μm) is detected in fine-grain structure crystallites using the bend extinction contour method. The effect of the initial film thickness and composition on the internal bending of the lattice grain is investigated. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The effects of melt temperature Ti and quenching rate Vi on the structure and optical properties of As2S3 glasses is studied. It is found that the glass band gap increases with Ti and Vi , whereas a decrease is observed in the glass density, refractive index (from 2.71 to 2.48), and two-photon absorption coefficient (from 0.37 to 0.15 cm/MW), which is accompanied by an increase in the optical-breakdown damage threshold. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The optical and electrical properties of thin arsenic chalcogenide As–Se and As–S films modified by rare-earth complexes with various organic ligands (europium trisdipivaloylmethanate Eu(thd)3 and lanthanide diethyldithiocarbamate Ln(ddtc)3 (Ln = Pr, Eu)) have been studied. It is shown that the use of mixed rare-earth complexes possessing saturated vapor pressures close to chalcogenide vapor pressures allows thermal evaporation growth of films that are promising for producing planar optical waveguides. It is found that the introduction of Eu(thd)3 complexes that incorporate oxygen into arsenic selenide decreases the absorptivity in the Urbach edge region and significantly decreases the conductivity activation energy, which is not characteristic of materials of this type. These results are attributed to the effect of oxygen on the medium-range order of the structure matrix. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Photoexcitation and photoluminescence (1–7 eV) spectra of amorphous carbon films grown by laser ablation of a graphite target have been measured. The experimental data obtained are analyzed using the sum rule, and the energy dependence of the effective electron density of states is determined. Characteristic threshold energies in the effective density of states are revealed at ∼1.4 and ∼4 eV, and the conclusion is made that the energy distribution of the density of states is nonuniform, which is attributed to different contributions from the σ and π states of electrons. The temperature of the electron system excited by light is estimated to exceed the lattice temperature by a factor of ∼40. This circumstance is attributed to heating of electrons by light. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has been employed to study spectra of the vibrational frequencies of carbon in the range 1000-1800 cm[sup -1] in amorphous carbon films modified with iron. The content of iron in a film has been set technologically by varying between the samples the area ratio of the graphite and iron parts of the target and monitored by Rutherford backscattering. Amorphous carbon layers containing 3, 26, 38, and 54 at. % iron have been obtained. The Raman spectra have the form of a broad band with features that are characteristic of amorphous carbon and lie at 1332 cm[sup -1] (D-band) and 1552 cm[sup -1] (G-band). At iron content of 38 and 54 at. %, the spectrum breaks up into a number of bands, which points to fragmentation of the matrix of amorphous carbon with increasing iron content. It is shown that the integral amplitude of scattering decreases nonlinearly with increasing iron content in a sample. The effect is analyzed in terms of a model that accounts for the linear dependence of the rate at which the number of atoms contributing to the scattering changes with the atomic fraction of carbon relative to the total number of carbon atoms in the film. [ABSTRACT FROM AUTHOR]

The formation of β-FeSi[SUB2] precipitates was observed for the first time in microcrystalline Si films. The Fe-doped amorphous Si films (a-Si:Fe) were obtained using magnetron sputtering. Subsequent short-time thermal treatment led to the transition of amorphous Si to microcrystalline Si and to the formation of β-FeSi[SUB2] precipitates. The samples synthesized emitted at the wavelength λ ≈ 1.54 μm at 100 K. [ABSTRACT FROM AUTHOR]

A comparative analysis of λ = 1.54 μm electroluminescent structures based on amorphous hydrogenated silicon is made. The possibility of obtaining room-temperature electroluminescence from forward-biased conventional p-i-n structures based on this material is demonstrated for the first time, which is of interest for the development of effective emitting structures with current pumping. [ABSTRACT FROM AUTHOR]

The conductivity of intrinsic amorphous hydrogenated silicon (a-Si:H) becomes higher upon gamma irradiation. This effect is due to an increase in the number of metastable D[sup +] states in the mobility gap. At the same time, the conductivity of extrinsic (undoped) irradiated a-Si:H decreases. Most likely, gamma irradiation creates hydrogen-containing complexes in this material. The results obtained are discussed in comparison with the known data for B- or P-doped a-Si:H. [ABSTRACT FROM AUTHOR]

It was found that the atomic-hydrogen treatment of n-GaAs epitaxial samples having initially highquality surfaces both with a SiO[sub 2] protective film on the n-layer surface and without it can lead to the amorphization of these surfaces and a thin (≈ 7 nm) surface layer, which is accompanied by the formation of a hydride phase. The lack of a hydrogen sublattice in the near-surface layer can imply that the main driving forces in the amorphization of epitaxial n-GaAs are short-range chemical interactions between hydrogen atoms and also between hydrogen atoms and atoms of the basic matrix of the crystal. [ABSTRACT FROM AUTHOR]

The effect of thermal treatment in a vacuum on the structure and properties of amorphous hydrogenated silicon (a-Si:H) films obtained by cyclic deposition with intermediate annealing in hydrogen plasma was studied, a-Si:H films deposited under optimal conditions are characterized by the nonuniform distribution of o the nanocrystalline phase (<1 vol %) across the film thickness and have the optical gap E[sub g] = 1.85 eV, the activation energy of conductivity E[sub a] = 0.91 eV, and a high photosensitivity (σ[sub ph]/σ[sub d] ≈ 10 under illumination of 100 mW/cm² in the visible spectral range). Transmission electron microscopy studies demonstrated that thermal treatment in a vacuum leads to blurring of the initial layered structure of a-Si:H films and to a somewhat higher amount of nanocrystalline inclusions in the amorphous phase matrix. Thermal treatment above 350°C causes a dramatic increase in the dark conductivity, as well as the resulting decrease in the photosensitivity, of a-Si:H films. [ABSTRACT FROM AUTHOR]

The effect of annealing on the electron density of states in amorphous carbon a-C and amorphous hydrogenated carbon a-C:H has been studied, a-C and a-C:H layers were grown by magnetron sputtering of a graphite target in, respectively, argon and argon-hydrogen plasmas. Optical transmission spectra were studied experimentally in the range 1.5-5.6 eV, and ellipsometric parameters were measured at the He-Ne laser wavelength. The spectral dependence of the imaginary part of the dielectric function was reconstructed. A model describing the optical response of amorphous carbon was developed on the basis of the hypothesis that there are fluctuations of the sp² fragment sizes in the allotropic composition of amorphous carbon. The optical gap E[sub g] in both types of material is accounted for by the presence of fragments of critical size. Experimental data were used to reconstruct, with the use of model parameters, the energy dependence of the density of states in the ground and excited bands, and the plasma frequencies for electrons involved in optical transitions are found. It is shown that the bands of both the ground and excited states are inhomogeneously broadened sets of levels, which are symmetrical about the Fermi level. The behavior of the model parameters E[sub g] and E[sub G] (energy corresponding to the peak of the Gaussian distribution) and the plasma frequency with annealing temperature shows, for materials of both types, a substantial rise in the size and number of critical fluctuations with increasing temperature. [ABSTRACT FROM AUTHOR]

Correlations were determined between the medium-range-order characteristic in an a-Si:H structure and the density of defects, their charge state, the optical band gap, and its spatial fluctuations. It was shown that the modification of the structure at the medium-range-order level, owing to the formation of nanoinclusions, can lead to a radical increase in photoconductivity and to ordering of the structure of the amorphous matrix. [ABSTRACT FROM AUTHOR]

X-ray and ultrasoft X-ray spectroscopy have both been applied to study SiK[sub β] and SiL[sub 23] emission spectra of crystalline silicon (c-Si), amorphous hydrogenated silicon (a-Si:H), and silicyne (a new allotropic linear-chain form of silicon). SiL[sub 23] spectra of silicyne show three peaks instead of two observed in crystalline and amorphous silicon. The third peak lies in the high-energy range at 95.7 eV, its intensity constituting ∼75% of that of the main peak. An additional peak is also observed in the short-wavelength part of the SiK[sub β] spectrum. Such a significant difference in shape between the X-ray spectra of amorphous silicon and silicyne is attributed to the existence of a pronounced π component in the chemical bonds between silicon atoms in silicyne. [ABSTRACT FROM AUTHOR]

The method for the structural modification of noncrystalline semiconductors consists in controlling the properties of these materials by changing their structure at a fixed chemical composition. It is shown that there exist at least four levels of structural modification distinguished by changes in the material structure: the levels of short- and medium-range order, morphology, and the defect subsystem. Each level of structural modification affects a certain group of properties. The possibility and efficiency of changing the structure at different levels of the above classification is analyzed for covalent semiconducting compounds of elements belonging to Groups IV-VI of the periodic table and some systems on their basis. Based on this analysis, the applicability limits of various levels of structural modification are determined. [ABSTRACT FROM AUTHOR]

The electrical and photoelectric properties of layered a-Si:H films obtained by cyclic plasmochemical deposition and the effect of thermal annealing on these properties have been studied. Unannealed films demonstrate high photosensitivity, with a photoconductivity to dark conductivity ratio of K = 3.4 × 10[sup 6]. Increasing the annealing temperature causes the film photosensitivity to fall because of a considerable decrease in the photoconductivity and increase in the dark conductivity. For films annealed at temperatures above 500°C, the conductivity is the sum of the band conductivity and the hopping conductivity via states at the Fermi level. [ABSTRACT FROM AUTHOR]

The thermal stability of amorphous carbon (a-C and a-C:H) has been studied by ellipsometry and spectrophotometry in the visible and near-UV range (1.5-5.6 eV). The dielectric function of amorphous carbon has been derived and analyzed using the Kramers-Kronig technique. The conventional analytical approach is shown to be insufficient for the analysis of thermally treated samples. The fundamental absorption edge is analyzed with respect to collective effects in nanoscale fragments of the graphite-like component of the amorphous carbon structure. Two types of graphite-like clusters contributing to the spectral dependence of the fundamental absorption edge and modified by thermal treatment are revealed. [ABSTRACT FROM AUTHOR]

Activation in IR absorption of quasi-Raman vibration modes of graphene planes was studied in a-C:H modified with copper; these modes are forbidden in the absence of copper. Parameters of the quasiRaman bands G and D in optical absorption in the region of carbon-carbon mode vibrational frequencies and the parameters of true Raman bands are compared in the Raman spectra of pure a-C:H and in that modified with copper. It is stated that the close coincidence of the frequencies of the true Raman bands in a-C:H and quasiRaman bands in a-C:H(Cu) indicates that the interaction of copper atoms with the carbon matrix leaves the graphene rings practically intact and can be regarded as intercalation. To identify the observed quasi-Raman and the satellite bands, correlations between their parameters are considered. The sizes of graphite-like clusters and their dependence on the copper content in the film were evaluated from the ratios between the integrated intensities of D and G bands. [ABSTRACT FROM AUTHOR]

The photosensitivity of heterojunctions formed by depositing thin amorphous films on silicon crystalline substrates is investigated. It is found that heterojunctions exhibit polarization photosensitivity, which is observed at an oblique incidence of the linearly polarized radiation on their receiving plane. The induced photopleochroism of heterojunctions increases quadratically with an increase in the angle of incidence θ and reaches 60% for θ = 80°. It is concluded that the heterojunctions obtained can be used as the broadband photodetectors of the linearly polarized radiation. [ABSTRACT FROM AUTHOR]

Thermal evaporation of tris(2,2,6,6-tetramethyl-2,5-heptadionato) Er(III) inside the plasma gap was used to introduce erbium into amorphous hydrogenated silicon (a-Si:H) obtained by radio-frequency silane decomposition. The samples obtained had a pronounced layered structure due to exhaustion of the erbium source. The layer nearest to the substrate was enriched with erbium, oxygen, and carbon; gave rise to luminescence with a wavelength of 1.535 μm characteristic of [sup 4]I[sub 13/2] → [sup 4]I[sub 15/2] intra-atomic transitions of erbium; and contained a large number of defects. The top layer contained much fewer defects, was close to undoped a-Si:H in the photoelectric characteristics, and was responsible for photoconductivity in the samples obtained. The experimental data are analyzed in the context of the models for doping of a-Si:H with Er with the resulting emergence of n-type conduction and formation of heterojunction as the film grows. [ABSTRACT FROM AUTHOR]

In this work we investigated the stability of a-Si:H films under illumination and following recovery in darkness at different temperatures. The a-Si:H films were fabricated with 55 kHz PECVD and with conventional rf 13.56 MHz PECVD. We measured the steady-state photocurrent and the dark-current after switching off the light source as a function of time. We observed photocurrent degradation and the following recovery of the dark current. The kinetics of the photocurrent degradation as well as the dark-current recovery demonstrated stretched-exponential behavior. The results of these straightforward measurements in combination with computer simulation were used to determine the effect of light-induced degradation and thermal recovery on the density of states distribution in the band gap of a-Si:H. We have found that the photocurrent degradation and the corresponding increase in the total defect concentration have different kinetics. The different kinetics were also determined for the dark-current recovery and the corresponding decrease in the total defect concentration. The results point out that slow and fast types of defects in a-Si:H films control the kinetics of light-induced changes of the defect distribution in the band gap. A model is proposed that relates the origin of the fast and slow metastable defects with the distribution of Si-Si bond lengths. [ABSTRACT FROM AUTHOR]

The photosensitive a-Si:H/p-CuInSe[sub 2] heterostructures were obtained for the first time by the deposition of hydrogenated amorphous silicon on polycrystalline p-CuInSe[sub 2] substrates. The photoelectric properties of the new system were studied. The conclusion was drawn on the prospects of the application of this system for solar and linearly polarized radiation photoconvertors. [ABSTRACT FROM AUTHOR]

Temperature dependences of the photoconductivity of boron doped a-Si:H films both prior to and after prolonged illumination were studied. It was found that the photoconductivity of films under study in the temperature range 200-300 K (intermediate temperatures) is independent of the doping level and the concentration of deep recombination centers (dangling bonds). A model of recombination is used to explain the experimental results; according to this model, the occupancy function of neutral dangling bonds in p-type a-Si:H (and, consequently, also the photoconductivity) is determined by the parameters of the states of the valence band tail and is independent of the doping level and of the total concentration of dangling bonds. [ABSTRACT FROM AUTHOR]

Photosensitivity of amorphous hydrogenated silicon films containing inclusions of Si nanocrystals, along with spectral characteristics of photoconductivity, were studied. A correlation between photosensitivity and features of the Raman spectra was established. The highest photosensitivity is observed in films with medium-range order formed to the maximum extent. [ABSTRACT FROM AUTHOR]

Current-voltage characteristics of electroluminescent structures composed of metal, erbium-doped amorphous silicon, and crystalline silicon and prepared by magnetron sputtering were measured and analyzed. It is shown that the carrier transport in a high-resistivity (a-Si:H):Er film (resistivity ∼10[sup 9] Ω cm) proceeds by the mechanism of unipolar-injection space-charge-limited currents controlled by two types of traps. Trap parameters, namely, the densities and ionization energies of acceptor and donor centers (∼10[sup 19] cm[sup -3] for both types of traps; 0.85-0.95 eV and 0.4 eV, respectively) are estimated by analyzing the current-voltage characteristics. In the light of the results obtained, the published excitation mechanism of erbium-related electroluminescence in such a material is discussed. [ABSTRACT FROM AUTHOR]

A new method for determining the spectral dependence of the optical-absorption coefficient in amorphous hydrogenated silicon is suggested. The method is based on the analysis of spectral and temperature dependences of transient photoconductivity in this material. Energy distribution of localized states involved in recombination of nonequilibrium holes was calculated. [ABSTRACT FROM AUTHOR]

The influence of implantation of Si[sup +] ions with energies of 30, 60, and 120 keV was studied on the dark conductivity, photoconductivity, hydrogen concentration, microstructure parameter, and special features of the ultrasoft X-ray emission spectra of a-Si:H films that were deposited at T[sub s] = 300°C by the dc-MASD and rf-PECVD methods and that differed in initial structural characteristics. [ABSTRACT FROM AUTHOR]

Growth behavior of a-C:H and a-C:H〈Cu〉 films produced by the magnetron sputtering of a composite target consisting of graphite and copper plates in an argon-hydrogen atmosphere was studied by infrared spectroscopy, scanning electron microscopy, and ellipsometry. The introduction of copper into amorphous hydrogenated carbon films was shown to cause no marked changes in the carbon-hydrogen bonds in the matrix. In the a-C:H〈Cu〉 films ∼2 µm thick, a thin uniform layer (∼1000 Å) was found to adjoin the substrate; closer to the free surface, the layer acquires a columnar texture with columns oriented from the substrate to the surface. The results of ellipsometry measurements were analyzed in terms of a two-layer film model. [ABSTRACT FROM AUTHOR]

The short-range-order structure and electron paramagnetic resonance of amorphous silicon prepared by vacuum sublimation and by ion implantation are investigated. It is found that amorphous silicon with atoms in the sp² hybrid state is formed in the annealing of evaporated silicon at 500 °C or in the irradiation of a silicon single crystal with neon at a dose greater than or of the order of 10[sup 17] cm[sup -2]. In the latter case the amorphous material is depthwise inhomogeneous and contains a layered structure consisting of silicon atoms with a period of 5.16 Å. In each case an ESR signal with a g factor g ... 2.0048, which corresponds to a dangling bond of a silicon atom in the sp² state, is observed. [ABSTRACT FROM AUTHOR]

The deposition of an amorphous ZnTe seed layer of thickness 10 nm and its subsequent solidphase crystallization are implemented prior to the start of molecular-beam epitaxy of ZnTe layers on GaAs(100) substrates. RHEED patterns from the growth surface of the samples during epitaxy confirm that the formation of three-dimensional nucleation centers is successfully eliminated by this technique, and two-dimensional growth in the early stage of epitaxy is achieved. Cathodoluminescence and x-ray structural analyses indicate a higher quality on the part of ZnTe layers grown with the application of an amorphous ZnTe layer. Quantum-well ZnCdTe/ZnTe structures that emit efficiently in the green region of the spectrum can be grown by optimizing the epitaxy regimes. [ABSTRACT FROM AUTHOR]

The redistribution of Er during its implantation in silicon at doses close to the amorphization threshold and its subsequent solid-phase epitaxial (SPE) crystallization is investigated. The formation of a buried amorphous (a) layer is discovered at Er doses equal to 5 x 10[sup 13] and 1 x 10[sup 14] cm[sup -2] using Rutherford backscattering. The segregation of Er in this case takes place inwardly from the two directions corresponding to the upper and lower boundaries of the buried αlayer and leads to the formation of a concentration peak at the meeting place of the two crystallization fronts. A method for calculating the coordinate dependence of the segregation coefficient k from the distribution profiles of the erbium impurity before and after annealing is proposed. The k(x) curve exhibits a drop, whose width increases with decreasing Er implantation dose. Its appearance is attributed to the nonequilibrium nature of the segregation process at the beginning of SPE crystallization. [ABSTRACT FROM AUTHOR]

a-C:H layers were grown by dc magnetron reactive sputtering of a graphite target in Ar + H[sub 2] plasma. Ellipsometric measurements were carried out and analyzed at a wavelength of 6328 Å for three sets of a-C:H layers with different thicknesses (different sputtering times) on silicon, fused quartz, and glass-ceramic substrates. It was shown that the substrate material had a substantial effect upon a-C:H growth: a-C:H layers on Si substrates were uniform up to ∼7000 Å thickness; for thin layers (<1000 Å) the growth rate was greater on quartz than on Si; the refractive index values of a-C:H were slightly different on quartz and Si substrates (1.60-1.65 and 1.65-1.72, respectively); a-C:H layers on glass-ceramic substrates were not uniform and had variable refractive index. [ABSTRACT FROM AUTHOR]

Investigations of transient photoconductivity in a-Si : H lead to the conclusion that tunnel recombination of localized excess carriers may predominate in the temperature range from liquidhelium temperatures up to temperatures at which the material was synthesized. [ABSTRACT FROM AUTHOR]

The near-gap electron spectrum and the effective charge distribution in graphite-like carbon nanoclusters of simple geometry in a-C : H containing a single Cu atom are calculated in the tightbinding approximation. Only the coupling between π electrons of the constituent C atoms and one valence s electron of the Cu atom is taken into account. The binding energy of the Cu atom in the clusters and the static dipole moment of the clusters are calculated. The results are invoked to interpret the experimentally observed activation of the Raman G band in the IR spectrum of a-C : H : Cu as a consequence of a lowering of the symmetry of the graphite-like clusters due to copper intercalation. Experimental data on the time dependence of the G band intensity during isothermal annealing of a-C : H : Cu are presented. The data suggest the possibility of reversible transfer of Cu atoms between the impurity states in the coppercarbon clusters and the impurity states in the purely copper clusters. The average activation energies of direct and reverse transfer are estimated from the experiment. [ABSTRACT FROM AUTHOR]

A variety of photostructural changes observed in tetrahedral and chalcogenide amorphous semiconductors are reviewed from physical and chemical points of view. In particular, observations of the photodarkening and related phenomena in chalcogenide glasses are summarized, and structural models which have been proposed so far are criticized. [ABSTRACT FROM AUTHOR]

A model of photoinduced optical anisotropy in amorphous semiconductors is studied theoretically. The change in the optical characteristics of a sample is associated with the photogeneration of geminate electron-hole pairs. If the pairs are generated by linearly polarized light, then the dipole moments of the geminate pairs lie mainly in the polarization plane, making the sample optically anisotropic. The model associates the optical anisotropy of the sample with the mean-square projection 〈P⊃[sub z]) of the dipole moment per unit volume on the polarization axis of the radiation. The evolution of 〈P²[sub z]〉 is determined by the kinetics of the drift and recombination of carriers in geminate pairs. The kinetics of the photoinduced anisotropy under continuous irradiation of the sample and its relaxation as a result of irradiation with pulsed polarized light is calculated. [ABSTRACT FROM AUTHOR]

The effect of radiation defects on the field and temperature dependences of the magnetic susceptibility of single-crystal Si was studied. A nonlinear magnetic-field-dependence of the magnetic susceptibility of irradiated Si was observed. This behavior can be explained by magnetic ordering of A centers. It was concluded that clusters of these centers with a local density of the order of 10[sup 21] cm[sup -3] exist. An explanation of the "diffusion paradox" in the formation of oxygen-containing thermal donors was proposed on the basis of micrononuniformities of the spatial distribution of thermal donors and interstitial oxygen in Si. [ABSTRACT FROM AUTHOR]