HOMOEPITAXIAL GROWTH OF ZNS SINGLE-CRYSTAL THIN-FILMS BY MOLECULAR-BEAM EPITAXY

Homoepitaxial ZnS single crystal films have been grown on ZnS(100) substrates at a low temperature of 260°C by molecular beam epitaxy using a high-temperature S beam heated up at 800°C. Crystallinity, surface morphology and growth rate of the films grown under various beam conditions (Zn beam pressure PZn=(0.1-1.8)x10-6 Torr, S beam pressure PS=(1.6-3.7)x10-6 Torr and beam pressure ratio PS/PZn=1-32) were investigated. Under the above beam conditions, the growth rate was independent of PZn, proportional to the square of PS, and was higher on (100)4°-5° off substrates than on (100) substrates. From these results, the growth kinetics were presumed to be governed by a pairwise interaction of S molecules with a Zn atom at a step site on the growth surface. ZnS single crystal films with good crystallinity and flat surfaces were successfully grown at high beam pressure ratios (PS/PZn > 4). On the other hand, crystallinity and surface morphology of the grown films became worse on decreasing the beam pressure ratio (PS/PZn<4) due to the excess Zn beam. © 1990.