Instability and (2×1) Reconstruction of Silicon Surfaces

Abstract

Publisher Summary Surfaces of diamond-like semiconductors, in particular silicon, are of prime interest for reconstruction. In general, the current approach has been the surface reconstruction of crystals exhibiting a certain component of covalent bonding, which have Shockley surface states (SS) around the Fermi energy E F . The importance of the electron–phonon interaction between SS and lattice deformations is assumed, and as the basic ingredient the electron (CDW or SDW) and lattice instability theory is used. The (2×1) instability is discussed by using the pairing theorem valid throughout the whole (2×1) surface Brillouin zone (SBZ) of surface and bulk electronic states of Si (111), (110), and (100) surfaces. As in the pseudo JT (Jahn-Teller) theory, main tool of the analysis is the (Umklapp) electron–phonon matrix element w kU = that operates as a symmetry based selection rule. In the chapter, |k> is the Bloch function and W is the electron–phonon (deformation) potential exhibiting same symmetry as the deformation mode η. For simplicity reasons, the case of a single SS band, appearing on the Si( 111) t × t surface is presented. Reconstruction of ideal Si(110) and (100) surfaces, where two SS bands occur in the gap is also treated easily, however, mainly results are mentioned.