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Sapphire Substrates for Micro- and OptoelectronicsDetails
Czochralski method is one of the most popular and widely used industrial methods for growing single crystals of semiconductor and dielectric materials, as well as synthetic crystals of gems. Technological features of the process are determined by the requirements to the geometrical parameters, structure, morphology and physico-chemical properties of single crystals.
There are systems of all-around automation of the crystal growth process based on Czochralski method. The main element of modern automated systems - the weight sensor with a high sensitivity, precision and reliability. This allows monitoring continuously the weight of the growing crystal, its dimensions and technological parameters of crystallization process in the process of growing.
Czochralski method has several advantages in comparison with other methods of crystallization:
• a high level of automation in the process of crystallization allows to conduct the crystallization process with minimal participation of the operator;
• the possibility of obtaining the single crystals of a given crystallographic orientation, with small deviations of the growth axis from this direction;
• availability of high temperature gradients in the melt at the crystallization front, providing conditions for the stability of a smooth crystallization front;
• sufficient simplicity of obtaining single crystals with a diameter to 50 mm with high optical and structural quality, which allows to use them for the manufacture of active laser elements;
• utilization of gas environments of crystallization with different redox chemical potential allows to grow single crystals of various chemical and stoichiometric composition;
• growth of the crystal from the melt occurs without contact with the walls of the crucible that allows to change the geometric parameters of the growing crystal and visually control its growth easily;
• method allows to set the geometric shape of the growing crystal by varying of the melt temperature and pulling rate;
• thermal units of Czochralski method is simple, reliable, low cost and efficiency in the operation.
The Institute of Single Crystals of NAS of Ukraine developed the method for growing high-temperature single crystals by Czochralski in ultrasonic acoustic field, which allows to have an influence upon the hydrodynamics and gas saturation of the melt actively. Specialists of the Institute grow scintillation crystals of heavy oxides CdWO4, PbWO4, PbMO4 by Czochralski.