CZT CRYSTAL GROWTH BY THM IN MICROGRAVITY - PREPARATION OF EXPERIMENTS FOR FOTON-M4 MISSION

摘要

Spaceflight conditions provide unique opportunities for growing high-quality crystals. The majority of defects in the crystal are caused by the gravitational convection (macro- and micro-heterogeneity of properties, inclusions of second phase, etc.). Furthermore, the effect of the hydrostatic pressure leads to a close contact of the melt with the crucible walls, causing thermal stresses and formation of dislocations during solidification. Microgravity conditions are attractive especially for growing ternary and quaternary crystals with homogeneous properties, in particular, Cd_(1-x)Zn_xTe crystals (CZT) with the content of ZnTe (x) of 8-15%. Large high-quality crystals of CZT are required for the production of a new generation of sensors for detectors of ionizing radiation. To study the effect of microgravity on the quality of the CZT crystals, two growth experiments are scheduled during the flight of the Russian automatic Foton-M4 spacecraft. This spacecraft was launched in 2014 for two months. Such long flight duration allows to carry out experiments that require long time, for instance, crystal growth from solution in the melt. Both CZT crystals would be grown by Travelling Heater Method (THM). The paper presents a description of the experiments, the results of mathematical simulation of crystal growth under terrestrial and space conditions. As a result of on-ground preparation, the technological parameters of space experiments (process temperature, growth rate, etc.) were determined.