Interaction of Se and GaSe with Si(111)

Abstract

Deposition of Se and GaSe on $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surfaces was studied with low-energy electron diffraction, x-ray photoelectron spectroscopy, and x-ray photoelectron diffraction to probe initial nucleation and interface structure for $\mathrm{GaSe}/\mathrm{Si}(111)$ heteroepitaxy. Room-temperature deposition of Se on $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ results in an amorphous film. Subsequent annealing leads to Se evaporation without ordering or interdiffusion. Se deposition at $450\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ saturates at submonolayer coverage with no diffusion of Se into the substrate. There is no clear evidence of ordered sites for the Se. Growth of GaSe on $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ above $500\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ results in a pseudomorphic bilayer, with Si-Ga-Se bonding. Additional GaSe does not stick to the bilayer above $525\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The resulting Se lone pair at the surface leads to an ideally passivated surface similar to $\mathrm{As}/\mathrm{Si}(111).$ This stable surface is similar to the layer termination in bulk GaSe. The single domain bilayer is oriented with the Ga-Se bond parallel to the substrate Si-Si bond.