R. G. Valeev

Structure and Properties of ZnSe Nanocomposite Thin Films

The structure and electrophysical and optical properties of semiconductor ZnSe nanocomposite thin films are studied. These films are obtained by discrete thermal evaporation in an ultrahigh vacuum. ZnSe films are synthesized in various structural states in the condensation temperature range 2–200°C. The optical spectra of these films are studied in the visible region.

EXAFS SPECTROSCOPY STUDY OF THE ATOMIC STRUCTURE OF ZnS NANOCOMPOSITE THIN FILMS

The atomic structure of zinc sulfide films obtained by thermal evaporation in ultrahigh vacuum at condensation temperatures of −100°C, −50°C, and 0°C was investigated. Structural states were assessed by means of X-ray diffraction and atomic force microscopy. Fourier transform was used to study the local atomic environment and acquire the structural information (interatomic distances and coordination numbers) by zinc K edge EXAFS spectroscopy.

EXAS Study of the Promising Semiconductor Material Ga 2 Se 3

Ga2Se3, a promising material for absorbing layers of high-efficient solar cells, is studied by EXAFS spectroscopy. Structural data (e.g., interatomic distances and coordination numbers) are obtained for the local environment of gallium and selenium, and are compared to modeling calculations performed using FEFF-8 software.

Study of the ZnS x Se 1– x @Al 2 O 3 nanostructures by X-ray diffraction and EXAFS spectroscopy

Nanocomposite systems based on ternary ZnSxSe1–x semiconductor compounds with different compositions (x = 0, 0.3, 0.5, 0.7, 1) in dielectric matrices of nanoporous anodic aluminium oxide (AAO) are synthesized by high vacuum thermal evaporation of a zinc sulfide and selenide powder mixture. The effect of the atomic concentration of solid solutions and the structural parameters of the AAO template matrix on the crystal structure of the synthesized nanocomposites and the local atomic environment of Zn and Se atoms is investigated.

Structural studies of ZnS:Cu (5 at %) nanocomposites in porous Al2O3 of different thicknesses

We present EXAFS, XANES, and X-ray diffraction data on nanoscale ZnS:Cu (5 at %) structures fabricated by the thermal deposition of a ZnS and Cu powder mixture in porous anodic alumina matrices with a pore diameter of 80 nm and thicknesses of 1, 3, and 5 μm. The results obtained are compared with data on ZnS:Cu films deposited onto a polycor surface. According to X-ray diffraction data, the samples contain copper and zinc compounds with sulfur (Cu2S and ZnS, respectively); the ZnS compound is in the cubic (sphalerite) and hexagonal (wurtzite) modifications. EXAFS and XANES studies at the K absorption edges of zinc and copper showed that, in samples deposited onto polycor and alumina with thicknesses of 3 and 5 μm, most copper atoms form the Cu2S compound, while, in the sample deposited onto a 1-μm-thick alumina layer, copper atoms form metallic particles on the sample surface. Copper crystals affect the Zn–S interatomic distance in the sample with a 1-μm-thick porous Al2O3 layer; this distance is smaller than in the other samples.

X-ray absorption fine structure and X-ray photoelectron spectroscopy studies of nanocomposite systems based on ZnS:Cu deposited into porous anodic Al 2 O 3 matrices

The results obtained via extended X-ray absorption fine structure and X-ray photoelectron spectroscopy studies of nanocomposite systems based on ZnS:Cu (5 at %) deposited into porous anodic alumina (AA) matrices, a promising material for electroluminescent light sources, are presented. The given results are compared with those corresponding to ZnS:Cu films on a smooth SiO2 surface. To implement the deposition process, we have pioneered the use of s method based on the thermal sputtering of ZnS and Cu powders mixed in a specified mass ratio. For the first time, ZnS:Cu single-crystal nanostructures are demonstrated to be formed in AA matrix pores. In this case, their size is assigned by the pore diameter and they possess better composition stoichiometry and better local ordering of atoms in the immediate environment of zinc.

Structural study of light-emitting nanocomposites based on ZnS:Cu deposited by explosive evaporation method on porous anodic Al2O3 matrices

In the work the results of structural studies of nanocomposite systems based on ZnS:Cu (5 at.% and 10 at.%) deposited by explosive evaporation on porous anodic aluminum oxide matrices fulfilled by EXAFS and X-ray phase analysis techniques have been presented. The composites under study are promising for applications in electroluminescent light sources. The results of the studies of emission intensity of light sources depending on frequency and amplitude of exciting field have also been presented.

EXAFS and XPS studies of germanium and gallium arsenide nanostructures in porous aluminum oxide matrices

The local atomic structure and chemical bonds of germanium and gallium arsenide, specimens of an isoelectronic series, are studied. Both materials are obtained via thermal evaporation of the materials’ powders onto porous matrices of anodic aluminum oxide and polycorr substrates. The mechanism responsible for the formation of local atomic structure is shown to be almost identical for Ge and GaAs. When compared to the films on polycorr surfaces, changes in local atomic structure are observed in the material obtained in porous matrices due to the difference between the mechanisms of condensation on rough and smooth surfaces.

Local atomic structure and chemical bonds of zinc sulfide and selenide nanostructures in porous aluminum oxide matrices

The local atomic structure and chemical bonds of ZnSe and ZnS nanocomposites are studied. Both materials are obtained via thermal evaporation of the materials’ powder onto porous matrices of anodic aluminum oxide and polycorr substrates. The mechanism responsible for the formation of the local atomic structure and the chemical bonds of zinc sulfide and selenide is studied. Relative to the films on polycorr surfaces, changes in the local atomic structure are observed in the materials obtained in porous matrices because of the difference between the mechanisms of condensation.

Characterizing ZnS x Se (1 − x ) films of various compositions via EXAFS spectroscopy

ZnSxSe(1 − x) (x = 0.36, 0.68, and 0.73) films of various compositions are prepared by the thermal deposition of a mixture of zinc sulfide and zinc selenide powders in ultrahigh vacuum. It is shown that the produced films and the source materials are close in chemical composition. The crystal structure of the films is studied via X-ray diffraction. The local atomic environment of selenium and zinc atoms is studied by means of EXAFS spectroscopy.