New Reconstructions on Silicon (111) Surfaces

We report the first observation of a class of new reconstructions on clean silicon (111) surfaces. The surfaces are prepared by a combination of laser and thermal annealing and the new structures are studied with a tunneling microscope. $c-(4\mathrm{}\times 2)\mathrm{and}(2\mathrm{}\times 2)$ regions populate the ordered parts of the surface directly after laser annealing. Subsequent partial thermal anneals result in a surface containing (5×5), (7×7), (9×9), and other intermediate structures. These observations' bearing on the connection between germanium and silicon reconstructions is discussed.