The Role of Redox Chemistry in Scanning Tunneling Microscopy Imaging of Electroactive Films.
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
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 31, 1995
- Accession Number
- ADA294315
Entities
People
- Henry S. White
- Shelly R. Snyder
Organizations
- University of Utah