COMPARATIVE AB-INITIO PSEUDOPOTENTIAL STUDIES OF (2X1) GROUP-V OVERLAYERS ON SI(001)

We present a comparative theoretical study of a single-monolayer cover age of the group V elements P, As, Sb and Bi on the Si(001) surface. T he generic (2 x 1) surface reconstruction, due to formation of symmetr ic overlayer dimers, is considered and a first-principles pseudopotent ial method is used. In addition to presenting well-relaxed structural data, we identify chemical trends in geometry, bonding and electronic structure in moving down the group V column of the periodic table. Ove rlayer-induced distortion of the substrate is found to decrease with i ncreasing overlayer atomic number. In general, P and As overlayer syst ems share many similarities, while Sb and Bi form another such natural pair. G novel feature of group V overlayers is that the bonding and o ccupied antibonding states formed by the dangling bonds lie very close in energy.