Structural models of the oxide layer on the Si(111) surface

Abstract

Two hand-built continuous random network structural models of the transition region between an Si(111) surface and an amorphous SiO₂ overlayer have been constructed. The models contain 354 and 329 atoms, respectively and differ in the degree of disorder. The transition region contains at least three atomic layers of SiO_x (0<x<2), and is characterized by a gradual change of the chemical composition from pure Si to SiO₂ and a relatively high deformation energy. The SiO₂ overlayer is probably fully disordered. The models were relaxed with respect to Keating and Coulomb forces; the latter led, however, only to minor changes of the structure. The bond angles at oxygen atoms have an average value of 144′ with an r.m.s. deviation of about 10°. The statistics of the Si(Si_4-nO_n) tetrahedra corresponds to the random-bonding model.