Surface reconstruction of ultrathin silicon nanosheets

Abstract: Si nanosheets are a promising candidate material for nanoscale devices but a thorough understanding of their surface properties is still lacking. Here we find, using first-principles molecular-dynamics calculations, a new surface structure specific to a double-layer Si nanosheet. The new surface structure, which can be labeled as Si(111)-2×2 in the same fashion as the bulk Si surface, is formed during surface reconstruction at finite temperature. The reconstructed nanosheet surface consists of highly distorted tetrahedra as on the Si(111)-2×1 surface, but its electronic band structure is markedly different from that of Si(111)-2×1. The vibrational properties of the reconstructed Si nanosheet are also found to reflect the distortion in the tetrahedral order. [Copyright &y& Elsevier]