ADSORPTION AND ELECTRIC MEASUREMENTS ON GERMANIUM(111) SURFACES COVERED WITH POTASSIUM AND CESIUM

Potassium and cesium adsorption on a Ge(111) surface and its effect on the surface conductivity, Δσ, surface recombination velocity, S, and work function changes, Δφ{symbol}, has been studied. The K and Cs Thermal desorption spectra consist of multiple peaks. To each peak corresponds a straight line segment of the Δφ{symbol} versus coverage curves. The surface conductivity versus coverage curves successively pass through a minimum and a maximum. The decreasing parts of these curves are attributed to the appearance of alkali-metal-induced extrinsic surface states, whereas the increasing one are ascribed to the disappearance of the intrinsic states of the clean Ge(111) surface. The surface recombination velocity has been found to be multi-valued function of the surface potential. At a K overlayer coverage close to one monolayer new high-temperature peaks appear in the TD spectra due to irreversible surface reconstruction. © 1979.