Morphology and interfacial properties of microrelief metal–semiconductor interface

The effect of the morphology of Au/GaAs interface microrelief, prepared by chemical anisotropic etching, on current flow mechanism, electronic and recombination properties of interface has been investigated. Simulation of I–V curves and optical transmittance of light into semiconductor was made on the basis of the developed theories taking into account the barrier height distribution and the effect of scattering of light by low microrelief.     

Morphology of the Si-ZnO interface

For Si-ZnO heterostructures, prepared by magnetron sputtering, the interface morphology is studied by XPS and UPS. ZnO films on Si(1 1 1) surfaces (H-termination and 7 × 7) were prepared by magnetron sputtering and metal organic molecular beam epitaxy (MOMBE) and are investigated in well defined deposition steps and the interface properties were studied in situ. All samples were handled in situ under ultra high vacuum (UHV) conditions. Up to five different interface phases were detected depending on ZnO preparation. Beside a SiO_x film induced by the sputter process, ZnO and Zn₂SiO₄ phases are resolved. In addition hydrogen, appearing as ZnOH_x, is found in considerable concentrations in the films.     

Electronic properties and atomic arrangement of the Ag/Si(111) interface

Variations of the work function and photoelectric yield spectra of a Ag/Si(111) system were investigated as a function of Ag film thickness and substrate temperatures. It was clarified that monolayer deposition of Ag onto Si at room temperature cause a decrease in the work function, while the deposition at 500°C did an increase. The results could be closely correlated with the atomic arrangement derived from low-energy ion scattering spectroscopy and low-energy electron diffraction.     

The influence of atomic steps on the photoelectric properties of clean cleaved silicon as derived from the surface photovoltage

The correlation of structural and electrical properties of clean silicon surfaces cleaved in UHV was investigated quantitatively by the surface photovoltage, using light with an energy larger than the band gap of silicon. The surface photovoltage, which is a function of band bending and recombination probability, depends strongly on the appearance of atomic steps. The additional surface states vary with density and crystallographic orientation of the steps as well as with adsorption of oxygen. The experimental facts can be explained by accepting a shift of the Fermi level at the surface towards the valence band due to edge atoms. By measuring the change of sign of the surface photovoltage of crystals with various dopings an exponential temperature dependence of the ratio of the recombination probabilities r_v/r_c for transitions from and into the Surface states has been derived.     

Geometries,spectra and photoelectric properties of trifluorenylamine-based photoactive layer

The ground-state geometries, electronic structures, spectra and photoelectric properties of two dyes (JA1 and JA2) used for dye-sensitised solar cells (DSSCs) have been investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT). For simulation of the realistic environment, we calculated the energy levels of molecular orbitals and absorption spectra in solvent, and the different electric fields have been considered. For interpreting the difference of photoelectric properties, we assessed the energy levels and energy gaps of frontier molecular orbitals, electron density, absorption, the total static first hyperpolarisability and driving force of electron injection. The relationship between structure and performance should be established. Furthermore, 24 dyes were designed on the basis of JA1 and JA2 to improve optical response and electron injection. The results of molecular modelling would provide the optional approach for improving performance of photoelectric materials.     

Breakdown of the high-energy atomic approximation of the photoelectric cross-section in graphite

The densities of the occupied and empty states of graphite have been studied by XPS and BIS. The spectra of the π states in the σ gap are completely asymmetric on each side of E_F, in glaring contradiction with the predictions of all band-calculations. It is shown that this observation must be attributed to interference effects in the matrix elements due to the presence of more than one atom in the primitive cell.     

A model for vibrational properties of the atomic interface in A/B fcc metals

The motivation of this theoretical work is to introduce a model calculation for the elastic waves scattering and coherent phonon transport at an atomic nanojunction between face-centered cubic (fcc) leads. The model system A/B consists of two perfect semi-infinite fcc leads A and B, oriented in the same direction and joined by an atomic interface. It is applied to the system Cu/Ni and its inverse Ni/Cu. A theoretical approach based on the matching method is used to study the dynamics of the system A/B.     

Some photoelectric properties of p-GaSe monocrystals

The thermostimulated conductivity, static characteristics, and kinetics of photoconductivity in undoped GaSe monocrystals with p-type conductivity are studied over the temperature range 80–350K. Photocurrent as a function of intensity and wavelength of exciting light, and relaxation curves are analyzed. Insignificant temperature and infrared photocurrent extinction was observed. The major parameters of photosensitive centers are determined. It is demonstrated that the experimentally observed principles of photoconductivity in gallium selenide can be explained within the framework of the two-center recombination model, as realized for many wide-zone photoconductors [1–3].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–70, January, 1976.     

The chemical composition of a metal/ceramic interface on an atomic scale: The Cu/MgO {111} interface

The chemical composition profile across a Cu/MgO {111}-type heterophase interface, produced by the internal oxidation of a Cu(Mg) single-phase alloy at 1173 K, is measured via atom-probe field-ion microscopy with a spatial resolution of 0.121 nm; this resolution is equal to the interplanar spacing of the {222} MgO planes. In particular, we demonstrate directly that the bonding across a Cu/MgO {111}-type heterophase interface, along a <111> direction common to both the Cu matrix and an MgO precipitate, has the sequence Cu|O|Mg... and not Cu|Mg|O...; this result is achieved without any deconvolution of the experimental data. Before determining this chemical sequence, it was established, via high-resolution electron microscopy, that the morphology of an MgO precipitate in a Cu matrix is an octahedron faceted on {111} planes with a cube-on-cube relationship between a precipitate and the matrix; that is, {111}_Cu//{222}_MgO and <110>_Cu // <110>_MgO.     

Optical,photoelectric and electric properties of single-crystalline Sb2Se3

Measurements of absorption coefficient in the region of the absorption edge, of spectral distribution of photoconductivity and dependence of electrical conductivity upon temperature on Sb₂Se₃ single crystals are given. The absorption of light was proved to correspond to indirect forbidden transitions. The value of optical gapE _g ^opt =(1·11±0·02) eV forE a andE c was determined. From photoconductivity and conductivity measurements the values of the gaps areE _g ^opt =1·11 eV andE _g ^el =1·04 eV. The anisotropy of the electrical conductivity parallel and perpendicular to the cleavage plane is 2·2.     

Formation of the Co/Si(110) interface: Phase composition and magnetic properties

The formation of the Co/Si(110)16 × 2 interface and its magnetic properties are studied by high-energy-resolution photoelectron spectroscopy using synchrotron radiation and magnetic linear dichroism in the photoemission of core electrons. It is shown that a cobalt coating less than 7 Å thick deposited on the silicon surface at room temperature results in the formation of an ultrathin (1.7 Å) interfacial cobalt silicide layer and a layer of silicon-cobalt solid solution. The ferromagnetic ordering of the interface is observed at an evaporation dose corresponding to 6–7 Å in which case a cobalt metal film begins to grow on the solid solution layer. During 300°C-annealing of the sample covered by a nanometer-thick cobalt layer, the metal film gradually disappears and four silicide phases arise: metastable ferromagnetic silicide Co₃Si and three stable nonmagnetic silicides (Co₂Si, CoSi, and CoSi₂).     

Optical and photoelectric properties of helical quantum wires

The appearance of a steady current in a helical quantum wire under circularly polarized light is predicted. The effect is associated with the appearance of a travelling electromagnetic wave in the coordinate system related to the wire, the wavelength being determined by the period of the helix. The gyrotropy of a medium consisting of parallel quantum wires is considered.     

Preparation and photoelectric properties of antimony selenium iodide

The dependence of the photoelectric current on the wave-length was measured on SbSeI crystals in the temperature range of 83–293°K. The maximum of the internal photoeffect was found in the region of 720–740 nm for various crystals at room temperature. The temperature dependence of the forbidden band width of SbSeI crystals was deduced from the shift of the photoeffect maximum. The results were compared with the properties of homological compounds SbSI and BiSI.     

Morphology,conductivity, and mechanical properties of polypyrrole-containing composites

An electrical-conducting polypropylene/polypyrrole (PP/PPy) composite was prepared by the chemically oxidative modification reaction of pyrrole on the surface of PP particles in suspension. Another type of PP/PPy composite was prepared by mixing the coated PP particles with noncoated PP particles at room temperature. The composites were processed by compression molding or by injection molding. The injection-molded composites exhibited better mechanical properties compared to compression-molded samples, while these composites showed better antistatic behavior and electrical conductivity. The differences in the behavior of the two types of composites were caused by the different structure of the PPy phase, which was studied by hot-stage optical microscopy and X-ray photoelectron spectroscopy (XPS).     

Electrical, optical, and photoelectric properties of electron-irradiated indium-doped cadmium sulfide single crystals

The effect of irradiation by 1.2-MeV electrons to a dose Φ=2×10¹⁷ cm^?2 on the electrical, optical, and photoelectric properties of In-doped CdS single crystals was studied. The experimental data obtained permit one to conclude that irradiation initiates decomposition of the supersaturated In solution in CdS, with the indium atoms at the sites of the cation sublattice being expelled by cadmium interstitial atoms. New slow-recombination centers were observed to exist in the irradiated CdS: In samples, with the maxima of optical quenching of the photoconductivity lying in the region of $\lambda _{M_1 } = 0.75\mu m$ and $\lambda _{M_2 } = 1.03\mu m$ . It is suggested that the new recombination centers are related to complexes containing cadmium vacancies and indium atoms.     

Radiative and photoelectric properties of CuInS2 single crystals

The photoluminescence and photocurrent spectra of CuInS₂ single crystals grown by the Bridgman method are studied at temperatures of 80 and 300 K. The photosensitivity spectrum is observed in the shortwave photoluminescence band. From the watt-ampere characteristics of photoconductivity, a linear mechanism of recombination of minority charge carriers is established for an illumination level of up to 100 mW/cm² in the temperature range of 80–300K.     

Some photoelectric and electrical properties of copper-doped gallium arsenide

A study has been made of the conditions for the formation of impurity centers having an ionization energy E _v + 0.1 eV in copper-doped gallium arsenide. Photoconductivity is demonstrated at 10.6 . The results of the photoconductivity study are used to calculate the absorption coefficient and cross section for photon capture by these impurity centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 40–44, September, 1970.The authors thank V. N. Detinko, A. S. Petrov, and A. P. Vyatkin for constant interest in this study.     

Some electric and photoelectric properties of p-type Si-CdSe heterojunctions

Russian Physics Journal -