AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS3-ThM

Paper SS3-ThM10
In-situ STM-studies of Solid/Liquid Interfaces:Growth of Ultrathin Compound Films

Thursday, November 18, 2004, 11:20 am, Room 213B

Session: Halogen and Oxygen Surface Reactions and Etching
Presenter: K. Wandelt, University of Bonn, Germany
Authors: A. Spaenig, University of Bonn, Germany
S. Huemann, University of Bonn, Germany
J. Hommrich, University of Bonn, Germany
P. Broekmann, University of Bonn, Germany
K. Wandelt, University of Bonn, Germany
Correspondent: Click to Email
Electrochemical Atomic Layer Epitaxy (ECALE) is quite an interesting alternative route for the synthesis of ultrathin layers, instead of vacuum based chemical vapour deposition techniques. This technique is based on alternating reductive and oxidative underpotential deposition (UPD) processes, e.g. of metal cations and halide or chalcogenide anions. In this contribution the growth of ultrathin semiconducting cadmium sulfide and insulating cadmium chloride films on Cu(111) and Cu(100) single crystal electrodes has been studied in-situ using an ElectroChemical Scanning Tunnelling Microscope (ECSTM). Atomically resolved ECSTM images are presented and discussed for the binary systems of either sulfide or chloride on Cu(111) and Cu(100) as well as for the ternary systems of cadmium sulfide and cadmium chloride on both surfaces. Chloride forms a (@sr@3 x @sr@3)R30° and c(2x2) adsorbate structures on Cu(111) and Cu(100), respectively, and has only a restructuring influence on the morphology of surface steps. In turn, sulfide forms several structures of low and high commensurability on both Cu surfaces, namely a c(2x6) on Cu(100) and a (@sr@7 x @sr@7)R19.1° and (2@sr@7 x 2@sr@7)R19.1° on Cu(111). Moreover at very positive electrode potentials sulfide induces severe reconstructions of both Cu surfaces with a checker-board like superstructure on Cu(100) and a hexagonal Moire like superstructure on Cu(111). Post-deposition of cadmium onto the chloride or sulfide pre-covered Cu surfaces leads to the formation of cadmium chloride or cadmium sulfide compound layers with interest periodic nanoscale superstructures whose physical properties are further characterized by ex-situ electron and ion spectroscopies.