Materials of Electronics Engineering (E-Journal) / Известия высших учебных заведений. Материалы электронной техники
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ВЛИЯНИЕ СОСТОЯНИЯ ПРИМЕСНЫХ ЦЕНТРОВ НА ЛАЗЕРНУЮ СТОЙКОСТЬ ЩЕЛОЧНО–ГАЛОИДНЫХ КРИСТАЛЛОВ
Get PDFThis paper reports results on the effect of Sr impurity on damage of crystalline potassium chloride under exposure to laser irradiation. The experimental data are accounted for using the photochemical model of laser damaging. We assume that the light scattering impurity centers are in the form of large aggregates of impurity/vacancy dipoles. The state of the impurity was monitored using light scattering. Under laser irradiation, photochemical reactions occur in the impurity centers, and the accumulating products of these reactions damage the crystals. We have found a correlation between the concentration of the impurity in the equilibrium impurity aggregates and the concentration of the damage initiating centers. We show that laser irradiation produces anion vacancies in impurity agglomeration areas and causes accumulation of F centers followed by the formation of colloidal quasimetallic particles on which specimen breakdown occurs. EPR spectroscopy revealed colloidal particles having quasimetallic properties
ИЗМЕНЕНИЕ СТРУКТУРЫ ПРИКОНТАКТНОЙ ОБЛАСТИ ТЕРМОЭЛЕКТРИЧЕСКИХ МАТЕРИАЛОВ НА ОСНОВЕ ТЕЛЛУРИДА ВИСМУТА ПРИ ПОВЫШЕННЫХ ТЕМПЕРАТУРАХ
Get PDFDestruction of the thermoelectric material on the basis of bismuth telluride under high temperatures, which prevents the use of these materials for a direct conversion of thermal energy into electrical energy, are revealed. Mechanisms of the occurring process are proposed. It is shown that the industrial technology of spark cutting leads to appearance of the damaged layer, which facilitates the penetration of solder into the volume of the thermoelectric material in subsequent soldering of thermoelements.Выявлены разрушения термоэлектрического материала на основе теллурида висмута под воздействием высоких температур, что препятствует при-менению этих материалов для прямого преобразования тепловой энергии в электрическую. Предложены механизмы про-текающих процессов. Показано, что промышленная технология электроискровой резки материа-ла приводит к возникновению нарушенного слоя, который при последующей пайке термоэлементов способствует проникновению припоя в объем термоэлектрического материала
О НАКОПЛЕНИИ ПРИМЕСИ В АДСОРБЦИОННОМ СЛОЕ В ПРОЦЕССЕ ЛЕГИРОВАНИЯ ПРИ МОЛЕКУЛЯРНО–ЛУЧЕВОЙ ЭПИТАКСИИ
Get PDFA kinetic model of the doping processes in molecular beam epitaxy is developed. The dopant incorporation into the growing crystal is assumed to occur via both blocking dopant atoms at the kink positions by the host atoms and atomic exchange between dopant adatoms and atoms of the topmost crystalline layer. The dopant surface segregation is treated as accumulation of dopant atoms in energetically favorable adsorption positions on the surface. Two segregation pathways are considered: climbing of dopant adatoms over moving steps and jumping of the dopants out of the topmost crystalline layer. It is shown that increasing supersaturation in the adlayer, e.g. with decreasing temperature or increasing growth rate, leads to more efficient blocking of the dopant atoms and, as a consequence, to the decreasing surface segregation. The supersaturation is partially reduced with appearance of 2D islands on the terraces and creation of kinks at the 2D island edges. This results in weaker growth rate and temperature dependences of the surface segregation ratio. Very strong (superexponential) dependence of the surface segregation ratio on the growth temperature is possible under the condition of the intensive jumping of the dopants out of the topmost crystalline layer. The reason is that the probability of «immurement» of the dopant atoms by the moving step depends exponentially on the jumping-out rate constant. The model reproduces experimentally observed segregation behavior of Sb on Si(100)
МЕССБАУЭРОВСКИЕ ИССЛЕДОВАНИЯ МАГНИТНЫХ ПОЛИМЕРНЫХ НАНОКОМПОЗИТОВ НА ОСНОВЕ МАГНЕТИТА И ПОЛИВИНИЛОВОГО СПИРТА
Get PDFОСОБЕННОСТИ ДЕФЕКТООБРАЗОВАНИЯ В ПРОЦЕССЕ ТЕРМООБРАБОТКИ БИЗДИСЛОКАЦИОННЫХ МОНОКРИСТАЛЛИЧЕСКИХ ПЛАСТИН КРЕМНИЯ БОЛЬШОГО ДИАМЕТРА С ЗАДАННЫМ РАСПРЕДЕЛЕНИЕМ В ОБЪЕМЕ КИСЛОРОДСОДЕРЖАЩИХ ГЕТТЕРИРУЮЩИХ ЦЕНТРОВ
Get PDFFor this purpose the opportunities of perfect layer formation during RTA have been analyzed in dislocation−free silicon wafers. The RTA application is based on an opportunity of effective influence on a distribution of oxygen precipitate density on wafer thickness by means of control of vacancies and interstitial atoms distributions. However the decision of this important task is connected with an oc-currence of large local wafer stresses concentrated near fastening supports and a significant bend of large diameter Si wafers. Therefore in this project the mathematical modeling of three−dimension strain state and defect formation in large diameter Si wafer were investigated: the various ways of wafer fastening were analyzed and the opportunities of stresses reduction in Si wafers were determined. For the description of RTA defect formation the mathematical model taking into account of diffusion−recombination processes of vacancies and interstitial Si atoms, and also formation of vacancy clusters have been applied. On the basis of this model the time thermal RTA parameters were determinated: heating mode, hold time at the maximal temperature and cooling rate of wafer. They provide a formation of required perfect layer near wafer surface contained the corresponding vacancy concentration and cluster density on wafer thickness. The calculated results have been verified by authors of this project on test samples investigated by Light Microscopy (LM) and Transmission Electron Microscopy (TEM). Detailed LM and TEM researches of microdefect distributions and morphology have been carried out for the experimental Si wafers subjected to various RTA modes and multistage heat treatment in Belarusian plant «Integral».
ДИАГНОСТИКА ТЕХНОЛОГИЧЕСКИХ ХАРАКТЕРИСТИК МОЩНЫХ ТРАНЗИСТОРОВ С ПОМОЩЬЮ РЕЛАКСАЦИОННОГО ИМПЕДАНС–СПЕКТРОМЕТРА ТЕПЛОВЫХ ПРОЦЕССОВ
Get PDFThe efficient method of determining thermal parameters in high-power field-effect transistors has been developed and tested based on a study of transient processes during self heating by direct current. With the developed relaxation spectrometer of thermal processes differential distribution profiles of thermal resistance of KP723G transistors have been investigated which were selected in accordance with the regimes of setting of their crystals. Thermal resistance spectra have been obtained from the analysis of time−dependent dynamic thermal impedance using a new non−destructive method of differential spectroscopy using higher order derivatives (order 3). We present both continuous (integral) and discrete spectra of the distribution of internal thermal resistance in the transistors and the value of the junction/case thermal resistance. Thermal characteristics of the KP723G transistors and their imported counterparts IRLZ44 and IRLB3036 have been determined. The method of determining the active area of devices has been developed and its decrease during heating has been shown. The proposed methodology is useful in solving technological problems of forming the setting layers of crystals and intermediate layers between a crystal and a heat sink and also for the development of thermal models in SPICE modeling of powerful MOSFETs and diode emitters
ИССЛЕДОВАНИЕ СТРУКТУРЫ КРУПНОГАБАРИТНЫХ МОНОКРИСТАЛЛОВ АНТИМОНИДА ГАЛЛИЯ, ВЫРАЩЕННЫХ МЕТОДОМ ЧОХРАЛЬСКОГО В КРИСТАЛЛОГРАФИЧЕСКОМ НАПРАВЛЕНИИ [100]
Get PDFThe properties of Chochralski grown [100] undoped GaSb crystals with diameters > 60 mm have been studied. We found that the dislocation density reduction in large undoped crystals can be achieved both by the well known technological approaches and by isovalent impurity (indium) doping. We show that the introduction of two additional annealing stages, one being close to the moment the crystal reaches the target diameter (the length of this stage is 1 hour, the temperature being close to the melting point) and the other being 3 h long post−growth annealing at 650 °C, reduces the dislocation density in ~60 mm diameter crystals to (3—5) · 103 cm−2. We found that dislocations in large GaSb crystals form in two distinct temperature ranges as evidenced by the difference in the morphology of the dislocation traces. The dislocation critical stresses were identified in the 420—690 °C temperature range. It is demonstrated that isovalent doping (In, concentration in the range (2—4) · 1018 cm−3 leads to a significant incr ase in dislocation critical stresses and, accordingly, to a drastic decrease in the average dislocation density to (4—5) · 102 cm−2. This opens new prospects for obtaining large low dislocation density GaSb crystals
ФОРМИРОВАНИЕ НАНОКОМПОЗИТОВ Ni/C НА ОСНОВЕ ПОЛИАКРИЛОНИТРИЛА ПОД ДЕЙСТВИЕМ ИК–ИЗЛУЧЕНИЯ
Get PDFThe work is dedicated to obtaining nickel metal-carbon nanocomposites, based on IR-pyrolyzed polyacrylonitrile and nickel chloride hexahydrate, and the study of the structural characteristics of the synthesized material. Nanocomposites prepared under IR-based precursor pyrolysis of polyacrylonitrile (PAN) and nickel chloride hexahydrate (NiCl2 • 6H2O). Pyrolysis was carried out in the temperature range 150—700 °C. The grown nanocomposites are two-phase system of the carbon matrix formed during carbonization of PAN, and distributed in the nanoparticles of nickel (nickel oxide). The average size of the nanoparticles in the nanocomposite was 15—25 nm. The effect of temperature pyrolysis process IR precursor in the size of nickel nanoparticles obtained. It was determined that the distribution of nickel nanoparticles in size is defined by the temperature of the synthesis of the nanocomposite. So while the temperature increases prevailing average particle size of the metal increases and the distribution is blured and shifts toward larger sizes. By a calculation of the total Gibbs energy of possible reduction reactions of nickel chloride and oxide pyrolysis products PAN the possibility of formation of nanocomposites comprising nickel oxide nanoparticles, which are at a higher temperature infrared heating (more than 5000 °C) can be reducted up to zero-valent state at more higher temperature IR heatig
ИССЛЕДОВАНИЕ МОРФОЛОГИИ И СТРУКТУРЫ ТОНКИХ ПЛЕНОК 3C–SiC НА КРЕМНИИ МЕТОДАМИ ЭЛЕКТРОННОЙ МИКРОСКОПИИ И РЕНТГЕНОВСКОЙ ДИФРАКТОМЕТРИИ
Get PDFSilicon carbide thin epilayers were grown on Si substrates by pulsed laser ablation of ceramic target. The influence of wafer temperature on morphological and structural properties of SiC layers was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffractometry.Методом вакуумного лазерного испарения керамической мишени получены субмикронные эпитаксиальные пленки карбида кремния на кремнии. Исследовано влияние температуры подложки на структурные свойства и морфологию поверхности экспериментальных образцов
О НЕКОТОРЫХ МЕТОДАХ ИНДУЦИРОВАНИЯ ВЫСОКОКОЭРЦИТИВНОГО СОСТОЯНИЯ В ЭПИТАКСИАЛЬНЫХ ПЛЕНКАХ МАГНИТНЫХ ГРАНАТОВ ДЛЯ ТЕРМОМАГНИТНОЙ ЗАПИСИ ИНФОРМАЦИИ
Get PDFResults of studying coercive force, optical absorption and lattice mismatch in single−crystal epitaxial magnetic garnet films are presented. It is shown that the reason of high values of both coercivity and optical absorption are the oxygen vacancies compensating Ca2+ ions and lattice mismatch stress. Methods of inducing high−coercivity state in Bi−containing garnet films through doping by bivalent impurity ions, through mismatch stress or through treatment in negative corona discharge are proposed. Merits and demerits of these methods are discussed and their comparison is carried out.Представлены результаты исследования коэрцитивной силы, оптического поглощения и рассогласования параметров кристаллических решеток в монокристаллических эпитаксиальных пленках ферритов−гранатов. Показано, что причиной высоких значений коэрцитивной силы и оптического поглощения являются напряжения несоответствия решеток и кислородные вакансии, компенсирующие катионыCa2+. Предложены методы индуцирования высококоэрцитивного состояния в Bi−содержащихгранатовых пленках путем легирования ионами двухвалентной примеси, за счет напряжений несоответствия и с помощью обработки в отрицательном коронном разряде. Проведено сравнение предложенных методов и анализ их достоинств и недостатков