Photoemission has been used to examine the formation of metal overlayers on sputter-annealed ZnSe(100)-c(2×2) surfaces for transition metals (Ti,Co), noble and near-noble metals (Cu,Ag,Au,Pd), a lanthanide (Ce), and a simple metal (Al). Analysis of Zn 3d core-level emission reflects metal-substrate interaction as well as substrate band bending as a function of metal coverage. Large differences in chemical behavior have been found. In particular, Ag and Au adatoms induce negligible Zn 3d core-level broadening, which is consistent with no substrate disruption. For the other metals, a second Zn 3d component reflects substrate disruption, and two reaction-induced components develop for Ti and Ce. The development of the Schottky barrier is compared with work-function variations. Very different Schottky-barrier heights have been found, ranging from 0.5 eV for Ce to 1.5 eV for Au and Pd. Neither the defect model nor the metal-induced gap-states model is able to describe all the experimental Schottky-barrier data. We do find a general correlation between the barrier height and the metal work function.

• Received 8 September 1988

DOI:https://doi.org/10.1103/PhysRevB.39.10744