Sulfide anion interaction with Cu(100) and Cu modified Au(100): An electrochemical STM study

We describe the formation of thin copper sulfide semiconductor films under electrochemical conditions. In a:first step we investigated the fundamental interaction of the Cu(100) surface with a sulfide ani ons containing electrolyte. Beside the classical p(2 x 2)-S and c(2 x 6)-S adlayer phases we found the formation of a closer packed pseudo-c(2 x 2)-S phase accompanied by an expansion of the topmost copper layer. For a further investigation of this pseudo-c(2 x 2)-S phase, we switched from the bulk Cu(100) electrode to a copper monolayer on a Au(100) elelctrode which can be easily prepard using copper underpotential deposition. Since such a copper monolayer is pseudomorphic to the Au(100) surface and therefore expanded by 12.5% with respect to the bulk Cu(100)-plane, exclusively a commensurate c(2 x 2)-S structure is instantaneously formed and remains stable over a wide potential range. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim