SXPS ANALYSIS OF PASSIVATION AND COMPLEXATION ON THE CDS (10(1)OVER-BAR-0) SURFACE

CdS(10 (1) over bar 0) surfaces were chemically modified by oxidation in air or UV/ozone, sulfurization after treatment with a Br-2-methanol solution and reaction with the multidendate organic reactant 2-mercap tobenzothiazole (MBT). Surface sensitive photoelectron spectra from tu ned excitation using synchrotron radiation (SXPS) show that initial ox idation by air gives monolayer coverages of sulfate (with minor contri butions of sulfite) and chemisorbed polysulfur species passivating the surface. In contrast to this behavior the oxidation by UV/ozone proce eds very fast, giving thick sulfate layers. Thick layers of elemental sulfur are created during Br2-methanol treatment. SXPS results show th at a monolayer of chemisorbed polysulfide between the sulfur coverage and the sulfide is only removed by annealing the substrate up to 500 K . The reaction of MBT with the CdS surface is photochemically activate d giving a submonolayer of MET/adsorbate complex covered by bis(2-benz othiazolyl)disulfide (BBTD). A scheme of the photoinduced oxidation me chanism creating the disulfide is proposed.