ADSORPTION OF BROMOCHLOROETHANE ON GAAS(100)

The adsorption of 1-bromo-2-chloroethane (BCE) on the Ga-rich GaAs(100 )-(4 x 1) surface has been studied using temperature-programmed desorp tion (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). At room-temperature, BCE was found to adsorb disso ciatively and TPD experiments suggest that the major species are ethen e (di-sigma- and pi-bonded configurations), chlorine and bromine. Adso rption at 170 K shows the multilayer physisorbed state, a weakly chemi sorbed molecular state, and a broad recombination peak spanning from 3 20 to 570 K, which was not detected for ECE adsorption at room tempera ture, Upon heating, the halogens are removed from the surface predomin antly as GaCl and GaBr for low BCE exposures, but at high exposures, A sCI desorption also occurs. As-2 desorption occurs for temperatures > 600 K when the surface becomes As-rich. The surface chemistry of the a dsorbed ethene is complex, with desorption of ethene, ethane and a cou pling product butane, being observed on heating.