Surface Reactions of Silicon (111) with Aluminum and Indium

Abstract

The chemisorption of indium on a clean silicon (111) surface has been investigated with display‐type low‐energy electron diffraction (LEED) equipment. Eight two‐dimensional phases have been observed. They vary with respect to composition (from one‐third to one monolayer) and with respect to dependence on thermal history. Transitions observed in the range between room temperature and several hundred °C occur with change in adsorbate concentration and reconstruction of adsorbate atom configuration, but transitions at much higher temperatures are probably accompanied by reconstruction of the adsorbing silicon atom configuration. It is noted that LEED provides specific means for determining composition. Combination of this information with the observed translational symmetry of a surface structure, the principle of bond saturation, and a choice of adsorbate sites of maximum symmetry makes the number of likely structures small for the simpler phases. Diffraction intensity data have been, for the most part, neglected as a means for structure analysis. Three cases of second‐order order‐disorder transitions were observed. It appears that interactions with the substrate cannot be neglected in order‐disorder models for at least one of these transitions. A curious phase with pseudotwelvefold rotational symmetry is described. A remarkable reconstruction of a silicon (100) surface into etch pits with (111) surfaces is illustrated with characteristic diffraction patterns.