PHYSICAL VAPOR TRANSPORT AND CRYSTAL GROWTH OF TELLURIUM: A NOVEL ACOUSTO-OPTIC MATERIAL

THE PROPOSED RESEARCH IS AIMED AT IMPROVING THE UNDERSTANDING OF THE EFFECT OF MICROGRAVITY ON VAPOR TRANSPORT AND CRYSTAL GROWTH. TO ACHIEVE THIS GOAL IT IS VERY IMPORTANT TO DESIGN AND OPTIMIZE SYSTEMATICALLY GROUND BASED EXPERIMENTS WHICH IS THE FOCUS OF THIS RESEARCH. THE PAST EXPERIMENTAL WORK ON THE SUBJECT HAS BEEN CARRIED OUT ON COMPOUNDS (I.E. HGI(2), GESE-GEI(4), GESE-XE). THE CHEMICAL COMPLEXITIES (BOTH IN VAPOR AND SOLID PHASE) INVOLLED IN THESE EXPERIMENTS MAKE IDENTIFICATION AND INTERPRETATION OF MICROGRAVITY EFFECTS OF TRANSPORT AND CRYSTAL GROWTH DIFFICULT. IN ORDER TO UNDERSTAND THE EFFECTOF NORMAL MICROGRAVITY AS VAPOR TRANSPORT AND CRYSTAL GROWTH, BRIMROSE PROPOSES A SIMPLER AND SCIENTIFICALLY STRONG EXPERIMENTAL SYSTEM. IN THIS SYSTEM TELLURIUM IS SUGGESTED AS A MODEL MATERIAL TO CARRY OUT RESEARCH ON PHYSICAL VAPOR TRANSPORT AND CRYSTAL GROWTH. TELLURIUM IS AN ELEMENT BELONGING TO GROUP VI OF THE PERIODIC CHART, HENCE IT IS CHEMICALLY SIMPLE AND DOES NOT INVOLVE COMPLEX VAPOR PHASE REACTIONS. MOREOVER, IT HAS A RELATIVELY LOW MELTING POINT (450 DEGREES CENTIGRADE) AND VAPOR PRESSURE SUFFICIENTLY HIGH TO CARRY OUT TRANSPORT AND GROWTH BY SUBLIMATION. ANOTHER INCENTIVE IS THE ATTRACTIVE APPLICATION OF HIGH QUALITY TELLURIUM CRYSTALS FOR ACOUSTO-OPTIC 10.6 UM LASER (CO(2)) BEAM MOULATORS AND STEERERS. THE RESEARCH INCLUDES A STUDY ON EFFECTS OF AMPOULE SIZE AND GEOMETRY, ORIENTATION WITH RESPECT TO GRAVITY AND TEMPERATURE GRADIENT IN HORIZONTAL AS WELL AS VERTICAL DIRECTION ON VAPOR TRANSPORT RATES ON CRYSTAL GROWTH. EXPERIMENTALLY TRANSPORT RATES WILL BE COMPARED WITH EXISTING THEORETICAL MODELS. THE VAPOR GROWTH CRYSTAL WILL BE CHARACTERIZED WITH RESPECT TO STRUCTURAL AND ELECTRICAL PROPERTIES.