Growth of Te on As-exposed Si(211) : Electronic structure calculations

Electronic structure calculations are performed to obtain energetically favorable As-exposed Si(211) and Te adsorbed As-exposed Si(211) surfaces. Arsenic-exposed Si(211) may be obtained by adsorbing As on Si(211) or by replacing surface Si atoms by As. First, we carry out systematic investigations to obtain stable As-exposed Si(211) due to As adsorption at various coverages. We find that at $1∕2$ monolayer (ML) coverage of As, the highly terraced Si(211) surface becomes flat decorated with parallel As chains extending along the $[01\overline{1}]$ direction. At 1 ML coverage the Si surface essentially retains its ideal structure with an added layer of As. Motivated by the adsorption sequence in the HgCdTe (MCT) growth on Si, Te adsorption on such an As-exposed Si(211) is studied and $1∕2$ ML of Te coverage is found to be energetically feasible. Next, we explore a stable As-exposed Si(211) upon replacement of surface Si atoms by As. An energetic comparison reveals that the As-exposed Si(211) obtained by replacing surface Si atoms with As is more favorable compared to that obtained by adsorbing As on Si(211). In line with the adsorption sequence in the MCT growth on Si, Te is then adsorbed on the most favorable As-exposed Si(211) and in contrast to the earlier situation, Te coverage here is found to be $1∕4$ of ML which agrees with the experiment.