Control Of The Polytypes And Line Defects In Radiation Detector Materials

Experiments were performed with pure and doped lead halides to investigate growth conditions for large crystals. Direct observations during the growth of 25 mm diameter crystal growing at high velocities showed that torodial type instability is formed at the solid/liquid interface during the growth. These instabilities translate into point defects and line defects. We report the results of extensive experiments on Lead bromide doped with silver bromide to study double diffusive transport. Control of instability at the interface provides a great improvement in the quality of crystal more specifically point defects and line defects. The controlled doping controls the defects and polytypism, and hence reduces the cracking and production of very large diameter good quality crystal is possible by Bridgman method. Results on the quality as the function of convection and growth parameters are reported in this paper.