Influence of surface reconstruction on Pb[sbnd]ZnSe interface formation

Abstract

This study addresses the growth and interface properties of the intimate PbZnSe contact using soft X-ray photoelectron spectroscopy. Metal films were deposited on two different ZnSe (001) reconstructed surfaces at room temperature, and the affect of subsequent in-situ annealing was monitored. The results suggest the absence of extensive PbZnSe reaction and interdiffusion, although the appearance of extra components in overlayer and substrate emission peaks suggest the formation of PbSe bonds at the interface for both reconstructed ZnSe surfaces. However, the thickness of this PbSe interface layer is strongly dependent on the surface stoichiometry, and this determines the subsequent metal growth mode. On the Zn-rich c(2 × 2) surface, a highly clustered Pb film was formed, while for the Pb layer grown on the Se-rich (2 × 1) ZnSe (001) surface, the PbSe interlayer is more prominent and the Pb growth mode is less clustered. On annealing, the desorption temperature of the Pb layer is similar, although a stable PbSe terminated surface was only observed for the initially Se-rich (2 × 1) ZnSe surface. This PbSe phase is fully desorbed at 480°C, leaving a disordered Zn-rich surface. The interface potential barrier was determined in each case from the substrate core level positions, and a small difference was consistently found between the two ZnSe surfaces. The barrier height for Pb is however significantly lower than for other inert metals on n-ZnSe.