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Abstract

The geometric structure of the -Ga(010)-(1x1) room temperature structure and its (2rootx2root2)R45° reconstruction below 232 K have been determined using low-energy electron diffraction structure analysis. The room temperature structure conforms to the cut-dimer model, forming a two-dimensional metallic structure with only minimal lateral displacements of the atoms. The topmost interlayer distance is 1.53 Å, corresponding to a spacing expansion of 2% from the bulk. In the low-temperature structure, the surface atoms shift to dimerize within the top two layers, resulting in a network of mostly covalent bonds, which form both parallel and perpendicular to the surface plane. The bond lengths of some of these dimers are about 10% shorter than the bond length found in the -Ga bulk and are thus shorter than any GaGa bonds reported so far.