Interaction of oxygen with a potassium-covered GaSb(110) surface at 500 K

The interaction of oxygen with a GaSb(110) surface precovered with 0.9 monolayers of potassium at 500 K has been studied by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and change of work function measurements. It is found that potassium can diffuse into the substrate and react with antimony atoms in the GaSb surface. At low exposures oxygen penetrates below the topmost layer, inducing a disruption of the K-Sb bonds and reacting with potassium, antimony and/or gallium to form their corresponding oxides (O2-). At th, same time, potassium atoms are gradually drown back to the surface with oxygen exposure. At higher exposure, potassium peroxide (O-2(2-)) on the surface is observed follow the formation of the monoxide K2O. The elevated temperature promotes oxygen diffusion into the substrate and delays the appearance of potassium peroxide, resulting in an increase of the saturated adsorption of oxygen, and this is beneficial for further oxidation of the GaSb surface. (C) 1999 Elsevier Science B.V. All rights reserved.