Accession Number : ADA294315

Title :   The Role of Redox Chemistry in Scanning Tunneling Microscopy Imaging of Electroactive Films.

Descriptive Note : Interim rept. Jun-Dec 94,

Corporate Author : UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY

Personal Author(s) : Snyder, Shelly R. ; White, Henry S.

PDF Url : ADA294315

Report Date : 31 MAR 1995

Pagination or Media Count : 28

Abstract : The dependence of tunneling current (i) on bias voltage (V(sub b)) in scanning tunneling microscopy (STM) measurements of multilayer electroactive films is interpreted in terms of a redox mechanism involving electron-transfer reactions at the STM tip/film and electrode/film interfaces. Analysis suggests that a symmetrical i-V(sub b) response is anticipated when the molecular film is sufficiently thick (approx.2- 3 monolayers) that the electron-transfer steps at the STM tip and electrode can be considered as discrete steps in the current- carrying processes. A macroscopic, two electrode, thin-layer electrochemical cell is used to mimic the response of an electrode/redox film/STM tip junction. Steady-state, symmetrical i-V responses are obtained for the thin-layer cell, even when the solution initially contains only one-half of an electroactive redox couple. Tunneling spectroscopic measurements, using a STM, of dry films of protoporphyrin(IX)Fe(Ill)Cl deposited on highly oriented pyrolytic graphite electrodes are interpreted in terms of the proposed redox mechanism. jg

Descriptors :   *SCANNING, *TUNNELING(ELECTRONICS), *THIN FILMS, *ELECTRON MICROSCOPY, *OXIDATION REDUCTION REACTIONS, METALS, MEASUREMENT, SPECTROSCOPY, INTERFACES, LAYERS, MOLECULES, CELLS, ELECTRONIC SCANNERS, FILMS, ELECTROCHEMISTRY, VOLTAGE, SURFACES, ELECTRODES, ELECTRON TRANSFER, BIAS, OPTICAL SCANNING, PYROLYTIC GRAPHITE.

Subject Categories : Solid State Physics
      Inorganic Chemistry
      Physical Chemistry
      Electricity and Magnetism
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE