S. N. Galkin

Dynamic chemical polishing of undoped and doped ZnSe crystals with H2O2-HBr-H2O solutions

We have studied the chemical interaction of the surface of undoped and doped ZnSe crystals with H2O2-HBr-H2O bromine-releasing solutions. The dissolution rate of the semiconductor materials has been measured as a function of etchant composition, stirring rate, temperature, and doping. The composition region of polishing solutions has been mapped out, and the surface condition after chemical etching has been examined by microstructural analysis. We have proposed and optimized polishing etchant compositions and conditions for chemical polishing of the semiconductors.

Professional and household dosimeters for UV biologically active ranges of solar radiation on the basis of ZnSe semiconductor-metal nanostructures

Development is reported of a small-sized ultraviolet (UV) radiometer designed for measurements of energy characteristics of UV radiation - energy illuminance and energy exposure. Main characteristics are considered of nZnSe(O, Te)/Ni Schottky structures created for the developed UV radiometer and used as UV sensors. Characteristics are presented of optical glass filters and interference light filters designed for separation of different biologically relevant UV spectral regions.

Effect of doping and heat treatment on the mechanical parameters of ZnSe(1 − x)Tex crystals grown from the melt

The mechanical properties of crystals of ZnSe(1 − x)Tex (0 < x < 1.3 wt %) solid solutions are investigated using the indentation method. The breaking points of doped and undoped crystals are measured by the uniaxial compression method. It is revealed that the microhardness anisotropy coefficient for crystals with a tellurium dopant content of ∼0.3 wt % is equal to unity. A change in the tellurium content in the solid solutions from 0.2 to 1.3 wt % leads to a linear increase in the microhardness by 23%. The brittle strength of the ZnSe and ZnSe(1 − x)Tex crystals varies in a similar manner. It is demonstrated that heat treatment and the presence of interblock boundaries affect the ultimate strength and the cracking resistance of the ZnSe(1 − x)Tex crystals. This is an important factor which should be taken into account in mechanical treatment of the materials under investigation.

Effect of Tellurium Doping on the Structural Perfection of ZnSe

Isovalent doping with Te is shown to have an advantageous effect on the structural perfection of ZnSe crystals, causing the wurtzite–sphalerite phase transition to reach completion. The optimum Te content of ZnSe crystals is 0.3–0.6 wt %. According to x-ray diffraction results, ZnSe1 – xTex crystals doped with less than 0.3 wt % Te contain twins and stacking faults. Doping with ≥0.6 wt % Te leads to tetragonal distortions of the ZnSe lattice.

ZnSe(Te)-based crystals and detectors for nondestructive testing and cargo inspection

Due to disadvantages of scintillator ZnSe(Te) - poor transparence to own emission (10-1 cm-1), long decay time, low density and Zeff-this material had no practical applications in the ranges of X-ray energies about 120-140 keV. After the development of dual energy X-ray inspection scanners, CT and digital radiography situation changed on the contrary at whole. Both theory and experiments show that now it is the best material for low energy array detectors. The pilot-industrial production of ZnSe(Te) crystals is organized, their usage in CT and inspection X-rays scanners being already started. It has become possible to get tomography imaging simultaneously with automatic recognition of dangerous objects and substances, which is due to the unique parameters of ZnSe(Te). Presently several leading western companies look for possibilities to use ZnSe(Te) for medical X-ray CT. Our aim was to unveil the nature of luminescence centers and the emission mechanism in crystals of ZnSe(Te) compounds with isovalent dopants from the results of our studies of optical, spectroscopic and kinetic characteriestics of these crystals. Basing on the obtained understanding of the emission centers, we aimed at creation of a reproducible production technology of scintillators for application in inspection and medical equipment. The research described in this publication was made possible in part by INTAS Project Ref. Nr. 05-104-7519.

Hot-pressed ceramic Cr/sup 2+/:ZnSe gain-switched laser

Technology of hot-pressed Cr/sup 2+/:ZnSe ceramic is reported. Comparative gain-switched lasing of hot-pressed ceramic and CVD grown Cr/sup 2+/:ZnSe with slope efficiencies up to 10 % and output energies up to 2 mJ was demonstrated.

Studies of interaction between components in system ZnSe-ZnTe-Se-H2-C

A thermodynamic analysis has been carried out for interaction of the components in the ZnSe-ZnTe-Se-H2-C system. Studies of thermodesorption, thermodynamics and kinetics of interaction reactions in the ZnSe-ZnTe-Se-H2-C system indicate high probability of formation of fine-dispersed fullerene-like particles of hydrated carbon black in this system at the stage of ZnSe(Te) charge synthesis. It has been established that carbon black particles preserve their stability at the stage of ZnSe(Te) crystal growth and can substantially affect crystallophysical, optical and physico-chemical properties of these crystals.

Thermodynamics of Chemical Interactions in the CdTe–ZnTe–O2–C System during Melt Growth of Cd1 – xZn x Te Crystals

Thermodynamic analysis is used to identify the possible chemical reactions of CdTe and ZnTe with the container material and gaseous atmosphere during Bridgman growth. Thermodynamic parameters of carbide and oxycarbide formation in the growth system are evaluated. The calculation results are consistent with the well-known fact that oxygen-containing impurities can be removed from the growth charge by calcination in hydrogen. Moreover, as shown in experiment, the removal of oxygen from the charge ensures a substantial decrease in the carbon content of the crystals.