The structure of Na adsorbed on Ge(1 0 0) and its influence on substrate morphology

We investigated the adsorption of sodium on the (1 0 0) surface of germanium with LEED, STM and electron spectroscopy (XPS). Upon adsorption at room temperature a metastable p(4 × 1) and a p(2 × 1) superstructure have been found. Annealing of these structures, accompanied by thermal desorption, results in the formation of a commensurate p(3 × 2) phase after an incommensurate state has been passed. The formation of structures observed after annealing requires the rearrangement of substrate atoms. In addition strong evidence was found that all ordered phases discussed in this paper contain one adsorbate atom per unit mesh.