Influence of surface reconstruction on Pb-ZnSe interface formation

This study addresses the growth and interface properties of the intimate Pb-ZnSe 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 Pb-ZnSe reaction and interdiffusion, although the appearance of extra components in overlayer and substrate emission peaks suggest the formation of Pb-Se bonds at the interface for both reconstructed ZnSe surfaces. However, the thickness of this Pb-Se 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 Pb-Se 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 Pb-Se terminated surface was only observed for the initially Se-rich (2 × 1) ZnSe surface. This Pb-Se 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.