THE INTERACTION OF GROUP-IB METALS WITH VAN DER WAALS FACES OF SEMICONDUCTING METAL DICHALCOGENIDES

The interaction of UHV cleaved van der Waals surfaces of the layered semiconductors SnS2, SnSe2, ZrS2, MoS2 and WS2 with deposited Cu, Ag and Au has been studied with XPS and LEED. It was observed for Cu on SnS2 and for Cu and Ag on SnSe2 that a bulk reaction occurs leading to the formation of a new phase containing reduced Sn and oxidized Cu or Ag. Even at high coverages a metallic overlayer was not formed. An interfacial reaction at low coverages and subsequently a metallic layer was obtained for Cu on ZrS2, Ag on SnS2 and Au on SnSe2. Cu, Ag and Au on MoS2 or WS2 form a metallic overlayer with an atomically abrupt semiconductor/metal interface. Epitaxial growth of a Au(111) layer was observed on WS2(0001). The differences in reactivity are related to differences in electrochemical standard potentials of the involved redox processes, structural features and to kinetic factors, e.g. ion transport.