SE GAAS(110) - ENERGETICS AND STRUCTURE

We present ab initio calculations based on density-functional theory o f the Se-deposited GaAs(110) surface for different coverages, theta = 1/4, 1/2, 1, and 3/2 and various structural models. In the submonolaye r case the highest adsorption energy is found for Se atoms bound in an interchain bridging position. For higher coverages we discuss a varie ty of adsorption models and compare these with exchange reactions in t erms of the thermodynamic stability. We observe a tendency for an exch ange of As and Se atoms in the uppermost layers and subsequent segrega tion of As at the surface. For the energetically most favoured structu res we compare the calculated band structures with data from soft X-ra y photoemission spectroscopy,