GROWTH-KINETICS AND MORPHOLOGY OF MERCURIC IODIDE-CRYSTALS GROWN BY PHYSICAL VAPOR TRANSPORT

The growth kinetics of mercuric iodide single crystals grown by physic al vapor transport from synthesized material were measured using an in strumented growth ampule, and in situ crystal size resolution to +/- 0 .2 mu m was achieved. The kinetic coefficients are 2 x 10(-4) mm/s and 1.3 x 10(-4) mm/s for (001) and (110), respectively, as found from ex trapolating the measured (apparent) kinetic coefficients to zero cryst al size. The kinetic coefficients are nearly independent of growth rat e in the practical range, approximate to 1-5 mm/day, indicating linear growth kinetics, and have substantial temperature coefficients of 0.3 x 10(-6) mm/(s degrees C) and 0.4 x 10(-6) mm/(s degrees C), respecti vely. The results indicate that the growth process is kinetically cont rolled at small crystal sizes and undergoes a transition to transport control at approximate to 30-40 mm crystal size, depending on the part icular face. The results are consistent with a layer spreading process of growth in which adsorbed molecules surface-diffuse with activation energies congruent to 4 kcal/mol and congruent to 8 kcal/mol for (001 ) and (110), respectively.