Formation of step density shock waves on vicinal NaCl(100) growth surfaces

The morphology of the growth surface near NaCl(100), formed during the pore motion in a crystal due to the temperature gradient, has been studied by the electron microscopic method of vacuum decoration. It is shown that at T = 950 K and Δμ/kΤ = 4·10⁻³, the profile of the vicinal surface in the direction is represented by monoatomic steps, while in the direction, as the surface curvature increases, there is a grouping of steps with the formation of macrosteps – bunches of elementary steps separated by areas of atomically smooth terraces. The sawtooth dependence of the step density on the longitudinal coordinate is described by a particular solution of the Burgers equation for a shock wave. Data on the parameters of three shock waves and the time of their formation are obtained.Електронно-мікроскопічним методом вакуумного декорування досліджена морфологія поверхні росту поблизу NaCl(100), що сформувалася під час руху пори в кристалі під дією градієнта температури. Показано, що при T = 950 K and Δμ/kΤ = 4·10⁻³ профіль віцинальної поверхні в напрямку представлений моноатомними сходинками, тоді як у напрямку , зі збільшенням кривизни поверхні, спостерігається групування сходинок з утворенням макросходин – згустків елементарних сходинок, розділених ділянками атомно-гладких терас. Пилкоподібна залежність густини сходин від поздовжньої координати описана частинним розв’язком рівняння Бюргерса для ударної хвилі. Отримано дані про параметри трьох ударних хвиль і час їх формування.Электронно-микроскопическим методом вакуумного декорирования исследована морфология поверхности роста вблизи NaCl(100), сформировавшейся при движении поры в кристалле под действием градиента температуры. Показано, что при T = 950 K and Δμ/kΤ = 4·10⁻³ профиль вицинальной поверхности в направлении представлен моноатомными ступенями, тогда как в направлении , по мере увеличения кривизны поверхности, наблюдается группирование ступеней с образованием макроступеней – сгустков элементарных ступеней, разделенных участками атомно-гладких террас. Пилообразная зависимость плотности ступеней от продольной координаты описана частным решением уравнения Бюргерса для ударной волны. Получены данные о параметрах трех ударных волн и времени их формирования

Optical parameters of the film naturally formed on the surface of cadmium telluride single crystals

Ellipsometric study of different surfaces of CdTe single crystals was carried out at a light wavelength of 632.8 nm. CdTe(110) crystals with cleaved surfaces after long time storage under ambient air conditions, Cd- and Te-terminated faces of (111) oriented CdTe crystals aged at room temperature in air during different times and samples chemically etched in a Br–HBr solution were investigated. The refraction and absorption indexes, and thickness of the films formed on the surface of different samples were obtained and the nature of these films was discussed. The ellipsometric measurement data have been well described by the two-layer model of a reflective system which includes (1) internal presumably pure Te layer with thickness of a few monoatomic layers and (2) external layer, probably Cd or Te oxide film of thickness from 5 to 10 nm depending on the time of storage in air

Modification of photoelectric and electrical properties of III-V semiconductors by pulsed laser irradiation

The effect of nanosecond ruby laser pulses on the photoelectric and electrical properties of GaAs and InSb single crystals with different pre-treated surfaces was studied. The photoconductivity, surface recombination rate and electrical resistivity of the samples have been analysed before and after irradiation with laser pulses characterized by a wide range of energy densites. An increase in the photoconductivity and decrease in the surface recombination rate of the investigated crystals was attributed to cleaning of the crystal surface and to the laser-stimulated desorption and segregation of electrically active defects at sinks. A considerable reduction in the resistivity of GaAs and a shift of the maximum and of the red edge of the photoconductivity specrtrum of InSb crystals toward shorter wavelengths were observed after irradiation with laser pulses of energy density above the melting threshold. The reasons for the found phenomena have been determined and the mechanism of the action of laser-induced stress and shock waves on the structure and properties of the crystals has been discussed