Interaction of Se and GaSe with Si(111)

Deposition of Se and GaSe on Si(111)7×7 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 GaSe/Si(111) heteroepitaxy. Room-temperature deposition of Se on Si(111)7×7 results in an amorphous film. Subsequent annealing leads to Se evaporation without ordering or interdiffusion. Se deposition at 450^∘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 Si(111)7×7 above 500^∘C results in a pseudomorphic bilayer, with Si-Ga-Se bonding. Additional GaSe does not stick to the bilayer above 525^∘C. The resulting Se lone pair at the surface leads to an ideally passivated surface similar to As/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.