The adsorption and desorption of CdI2on InSb(001): observation of an epitaxial orientational relationship

Abstract

A LEED, AES and ARUPS study has been made of CdI₂ adsorbed on the clean In-rich InSb(001) c(8*2) reconstructed surface at room temperature. A chemisorbed p(2*1) structure formed which consisted of a double layer of iodine atoms with cadmium atoms between them. It is suggested that this surface consists of linear I-Cd-I molecules aligned perpendicularly to the surface. Continued adsorption caused growth of an orientational relationship epitaxial layer of CdI₂. The epitaxial layer had the basal plane of the layered CdI₂ material parallel to the InSb(001) surface, with the hexagonal mesh of the CdI₂ at an angle of approximately=7 degrees to the square net of the substrate. On heating to approximately=400 K the epitaxial layer desorbed leaving a p(2*1) structure identical to that formed during adsorption. The p(2*1) was stable to 433 K beyond which further loss of Cd and I caused a change to a (1*1) structure. This structure is thought to consist of a (1*1) monolayer of iodine with Cd below the iodine layer, possibly incorporated into the substrate. Heating to 500 K caused complete loss of iodine and cadmium from the surface and the formation of a clean, Sb-rich surface.