Chemisorption of group-III metals on the (111) surface of group-IV semiconductors: In/Ge(111)

We have studied the surface reconstructions of the In/Ge(111) system by means of scanning tunneling microscopy, low-energy electron diffraction, and Auger electron spectroscopy. In atoms at the interface substitute the top-layer Ge atoms at all coverages and tend to relax downward, thus causing a compressive surface stress. To release the stress, some of the top-layer Ge atoms may be missing and some new lateral bonds may form between the second-layer Ge atoms. Depending on the concrete way of stress relief, which may vary with the In coverage, different surface reconstructions may form. Detailed atomic structural models for the striped and hexagonal structures of the system have been proposed for further studies. Comparing the information gathered from previous papers concerning the systems of group-III metals adsorbed on (111) surfaces of group-IV semiconductors, we suggest that the above mechanism might also be responsible for formation of the reconstructions of the III/IV(111) systems in general, at least when the coverage is around 0.5 ML.