Stability, local structure and electronic properties of borane radicals on the Si(1 0 0)

Abstract

Deposition of a thin B layer via decomposition of B2H6 on Si (PureB process) produces B-Si junctions which exhibit unique electronic and optical properties. Here we present the results of our systematic first-principles study of BHn (n = 0–3) radicals on Si(1 0 0)2 × 1:H surfaces, the initial stage of the PureB process. The calculations reveal an unexpectedly high stability of BH2 and BH3 radicals on the surface and a plausible atomic exchange mechanism of surface Si atoms with B atoms from absorbed BHn radicals. The calculations show strong local structural relaxation and reconstructions, as well as strong chemical bonding between the surface Si and the BHn radicals. Electronic structure calculations show various defect states in the energy gap of Si due to the BHn absorption. These results shed light on the initial stages of the complicated PureB process and also rationalize the unusual electronic, optical and electrical properties of the deposited Si surfaces.