On the adhesion of In 0.2 Ga 0.8 Sb to quartz ampoule during synthesis

In0.2Ga0.8Sb has been synthesized and polycrystals have been grown by the vertical Bridgman technique. Sticking of ingot to the quartz ampoule and ampoule cracking have been found to be major problems. The presence of native oxides on the surface of the starting material impedes the formation of homogeneous compounds due to which the structural quality of the ingots is poor. Worst sticking is observed with improper homogeneization and when excess of pure indium is present on the surface of the crystal. Several procedures have been adopted to avoid sticking and cracking. The most efficient way of solving this problem is to employ a high-temperature baking in dynamic vacuum prior to synthesis by placing the ampoule in a region of the furnace with a temperature gradient. The post-baking cooling rate is also extremely critical to avoid cracking. The polycrystalline alloy thus formed by adopting the pre-synthesis baking cycle shows better homogeneity and structural quality.