Double-Layer In Structural Model for the In/Si(111)-√7 x √3 Surface

We demonstrate by using density functional calculations that the In/Si(111)-root 7 x root 3 surface consists of an In double layer, contrary to the prevailing idea that the In overlayer on this surface is just one atom thick and thus can be used to represent the ultimate 2D limit of metal overlayer properties. The double-layer In structure is sound energetically and microscopically and, above all, well reproduces the measured photoemission band structure that could not be fairly compared with any single-layer In model. The present double-layer model urges a reconsideration on the recent experimental claims that the In overlayer properties were pushed to a single-layer limit in this surface.