SITE-SPECIFIC CHEMISTRY OF CARBON-TETRACHLORIDE DECOMPOSITION ON GAAS(001)

The site-specific chemistry of carbon tetrachloride decomposition on G aAs(001) (2 x 4) and (4 x 2) surfaces was studied by scanning tunnelin g microscopy and multiple internal reflection infrared spectroscopy of adsorbed hydrogen. By monitoring the changes in the vibrational spect ra of the As and Ga hydrides upon the coadsorption of CCl4, it was dis covered that this molecule dissociatively adsorbs onto Ga dimers and s econd-layer Ga atoms at 473 K. Upon heating to 673 K, the chlorine des orbs from these sites as GaCl, thereby reducing the Ga coverage. Scann ing tunneling micrographs reveal that GaCl desorption produces a highl y disordered (2 x 4) surface, and transforms the (4 x 2) into a new (3 x 2) reconstruction. The (3 x 2) surface appears to be stabilized by carbon incorporation.