Electronic and vibrational properties of the K/GaAs system

Abstract

The adsorption of K atoms onto cleaved GaAs(110) surfaces has been investigated in the monolayer coverage range by AES, EELS and HREELS. Before the completion of the first K-monolayer several distinct steps have been observed in the adsorption kinetics. Each step has been characterized by a careful analysis of the Auger lineshape and loss structures of both overlayer and substrate atoms. There is a strong evidence of a ionic-to-metal transition in the state of K adatoms in the first exposure range, and of the formation of a reacted interface at higher exposures with As out-segregation. A HREELS investigation has also been performed, with particular interest in the modifications induced by the presence of the K overlayer at different coverages, in the quasi-elastic peak width and in the surface phonons and free carrier plasmons, with respect to the clean surface. Measurements have been carried out at different primary beam energies, to exploit the different probing depth.