“The Thermal Wave” in Technology of Crystal Growth from the Melt

It was found that the temperature fluctuations at the interface crystal-melt are the main reason for the formation of single crystals inhomogeneity grown by the Czochralski method. To reduce the heterogeneity of the layered method is proposed to reduce temperature fluctuations in the melt through the creation of artificial heat wave formed by the modulation of the heater temperature setting of growing single crystals. This paper describes the experimental technique to measure the temperature directly in the field of crystal growth of gallium arsenide from the melt. We investigated the possibility of special control actions for decreasing the temperature fluctuations at the crystallization front. These actions relate to the modification of the thermal and kinetic control parameters normally used in the Czochralski method of crystal growth, such as heater temperature, as well as crystal and crucible rotation rates. Unsteady low energetic thermal control actions (thermal waves, induced by periodic changes of the heater temperature) are able to eliminate temperature fluctuations near the crystal / melt interface and may be a potential tool for the growth of striation-free gallium arsenide single crystals. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3364

Crystal Growth Mechanism in" Synthesis-solute-diffusion" Method in Ultrasonic Field

Features crystal growth method “synthesis-solute-diffusion”when applied ultrasonic field are consid-ered. Dependence of the crystal optical transmission heterogeneity frequency ultrasonic vibrations deter-mined. System Tests showed that the optimal vibration frequency that provided a homogeneous crystals and permitting the maintenance of the solidification front in a predetermined position with an accuracy of ±5% frequency is 4 MHz±5. Comparison of the optimum frequency ultrasonic vibrations to increase uni-formity in the mode of crystals convective transport under the Czochralski method and conditions of diffu-sive transfer method indicates a significant difference between these frequencies, i.e. character determines the transfer conditions of optimization process. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3632

Morphological Features of Gallium Arsenide Crystals Grown at Low-frequency Influences to the Crystallization Front

It was found experimentally that on the initial part of crystal the fluctuations with amplitude more than 1 mm leads to break of the capillary column melt and close of growth. The physical significance of this functional relationship for this probably lies in the different orientation of surface tension forces. Regar d-less of the direction of stretching and an amplitude -frequency characteristics of development process of the power of the octahedral facets increased with increasing growth rate. Accidents on existing ideas are the result of periodic growth, due, for example, the rotation of the crystal in an asymmetric thermal field. When carrying out the method of crystal growth with perturbations at the interface it to a solid phase, the lateral surface is also composed of corrugations distinguishable to the naked eye.In general, the study of structural defects in the crystals obtained in exacting heat conditions, showed that in this case, low-frequency disturbance of the melt at the interface reduces the average density of dislocations due to the periodic melting of crystallization and partially “heal" the defective portions of the crystals. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3633

Gallium Arsenide Czokhralski Crystal Growth with High Oscillatory Influences

The influence of ultrasound introduced into the melt during the growth of single crystals of gallium ar-senide. Ultrasonic vibrations had a frequency of 820 kHz and amplitude of 0.1-0.2 micrometer. Found an increase in the homogeneity of impurity distribution of the bands growth without change of the dislocation structure of single crystals. In the simulation result of the ultrasonic wave interaction with the melt in the crucible on the basis of the theory of formation of phases is established that nucleation rate associated with the frequency and amplitude of the ultrasonic vibration acting on the melt. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3632

The Synthesis of Metalcarbon Nanocomposite Ni / C on the Basis of Polyacrylonitrile

Metalcarbon nanocomposites based on polyacrylonitrile and nickel chloride are synthesized under the influence of infrared heat. The resulting materials represent a system of carbon matrix formed during the carbonization of PAN, and distributed in it nickel nanoparticles. The average size of the nanoparticles in the nanocomposite was 15-25 nm. It was found that the distribution of nickel nanoparticles sizes is determined by temperature synthesis nanocomposite. Thus with increasing temperature, the predominant average particle size of the metal increases, and the distribution is spread and shifted toward larger sizes. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360

Influence of the Ratio of Metal Composed Nanocomposites Fe-Co / C on Phase Composition

Metalcarbon nanocomposites based on polyacrylonitrile and nickel chloride are synthesized under the influence of infrared heat. The resulting materials represent a system of carbon matrix formed during the carbonization of PAN, and distributed in it nickel nanoparticles. The average size of the nanoparticles in the nanocomposite was 15-25 nm. It was found that the distribution of nickel nanoparticles sizes is determined by temperature synthesis nanocomposite. Thus with increasing temperature, the predominant average particle size of the metal increases, and the distribution is spread and shifted toward larger sizes. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360

Model of Band Diagram LED White Light in the System of GaN/InGaN

The results of the research of semiconductor multilayer nanostructures suitable for making white light LEDs in the GaN/InGaN with red, green and blue emission spectra formed in a single chip. The methodology and the calculation of the energy levels, the wave functions of the carriers, the electric fields caused by the spontaneous polarization and the piezoelectric effect, the spontaneous emission spectrum and chromaticity coordinates of the total radiation