Variation of the electronic and adsorption properties of GaAs(100) in the transition from an As-to Ga-rich surface

This paper reports on a threshold photoemission study of the variation of electronic properties occurring as Cs is adsorbed on GaAs(100) and the surface transfers gradually from the As-to Ga-rich state. The ionization energy and integrated photoemission current are studied as functions of the Cs coverage. The minimum of ionization energy and the corresponding Cs dose are established to differ substantially for the As-and Ga-rich GaAs(100) surfaces. The first observation is reported of anomalous curves with two ionization-energy minima, which are characteristics of surfaces in an intermediate state, with Ga and As dimers present. The sticking coefficient of Cs to the surface enriched in As is found to be several times smaller than that for the Ga-rich surface.