ADSORPTION, THERMAL-REACTION, AND DESORPTION OF DISILANE ON GE(111)-C(2X8)

Room-temperature adsorption of disilane (Si2H6) on Ge(111)-c(2 X 8) an d subsequent thermal reactions and desorption at elevated temperatures were studied using scanning tunneling microscopy and core-level photo emission. The initial adsorption results in the formation of various s urface radicals, and the reacted areas on the surface grow laterally f or increasing exposures. The sticking coefficient is rather low, and a n exposure greater than about 30 000 langmuirs is needed to saturate t he surface. The net amount of Si deposited for the saturated surface i s about one-half of an atomic layer. Thermal annealing causes the hydr ogen atoms to desorb and the Si atoms to move below the surface. For a nnealing temperatures beyond about 630 K, the desorption of hydrogen b ecomes complete, all of the Si atoms move below the surface, and the r esulting surface resembles the starting clean Ge(111)-c(2 X 8) surface except that the c(2 X 8) long-range order is partially destroyed. Ste p flow and island coarsening, similar to growth by molecular-beam epit axy, are observed.