抄録
A method is devised for growing ZnS crystals by sublimation. Large single crystals, about 1g_??_10g in weight, are synthesized by the following procedures. Polycrystals of easy grain growth are first prepared from a charge of ZnS powder by sublimation and recrystalization in a steep temperature gradient zone of a furnace. These polycrystals are piles of needle-like or rod-like grains with growth surfaces of the same orientation. The grains grow larger by heat treatment in saturated vapor of ZnS and single crystals are cleaved from the polycrystals.
Chemical components of the single crystals are not always in stoichiometric relation; hence impurity levels arise. The weight percentage of Zn in ZnS increases as the growth temperature of the crystals becomes higher.
Grain growth is discussed. When the vapor is cooled and recrystalized to be polycrystals in a zone with steep temperature gradient, the grains grow faster in the direction of temperature gradient. The grain boundaries in such a case are presumably very unstable and grains grow with ease by heat treatment. It is the reason why steep temperature gradient is needed in the recrystalization zone. Grains grow parallel to (1120) plane with the planes belonging to (1120) zone as the surfaces of growth. The grains with c-axes directing to temperature gradient are eaten away easily by the others as grain growth proceeds.
