Correlation of electron-transfer rates with the surface density of states of native and anodically grown oxide films on titanium

• Published in: Journal of physical chemistry (1952) Vol. 95; no. 18; pp. 7002 - 7007
• Main Authors: Casillas, Norberto, Snyder, Shelly R, Smyrl, William H, White, Henry S
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 05-09-1991
• Subjects: 360202 - Ceramics, Cermets, & Refractories- Structure & Phase Studies; 400400 - Electrochemistry; Applied sciences; CHALCOGENIDES; Chemical and electrochemical properties; CHEMICAL REACTIONS; CHEMISTRY; COMPLEXES; CRYSTALS; DATA; DIENES; ELECTROCHEMISTRY; ELECTRON TRANSFER; ELECTRONIC STRUCTURE; ELEMENTS; ENERGY GAP; Exact sciences and technology; EXPERIMENTAL DATA; FERROCENE; HYDROCARBONS; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON COMPLEXES; KINETICS; MATERIALS; MATERIALS SCIENCE; MATHEMATICAL MODELS; METALS; Metals. Metallurgy; MILLER INDICES; MINERALS; MONOCRYSTALS; NUMERICAL DATA; ORGANIC COMPOUNDS; OXIDATION; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; POLYENES; RADIOACTIVE MATERIALS; RADIOACTIVE MINERALS; REDOX POTENTIAL; RUTILE; THEORETICAL DATA; THIN FILMS; TITANIUM; TITANIUM COMPOUNDS; TITANIUM OXIDES; TRANSITION ELEMENT COMPLEXES; TRANSITION ELEMENT COMPOUNDS; TRANSITION ELEMENTS; Crystal growth; Density of states; Electrochemical properties; Electron transfer; Anodic oxide; Physical properties; Tunneling spectrometry; Native state; Titanium Oxides
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100171a051

Tunneling spectroscopy (TS) and surface density of states (SDOS) plots (dI/dV)/(I/V) vs. V) are reported for native and anodically grown titanium dioxide (TiO sub 2 ) films on polycrystalline Ti. The results are compared to data obtained by using single-crystal TiO sub 2 (001) and (110) surface orientations). SDOS plots for anodically grown TiO sub 2 films (160 A thick) and single-crystal TiO sub 2 show a large bandgap region ( approx 2 eV) with a low state density separating the conduction and valence band edges. The similarity in the distribution of SDOS for anodically grown TiO sub 2 films and single-crystal TiO sub 2 indicates that the anodically grown film has a well-ordered rutile structure. In contrast, SDOS plots obtained on native TiO sub 2 films show a nearly constant density of states over a 5 eV range and a approx 20-50 fold increase in state density at energies corresponding to the bandgap region of anodically grown films and single-crystal TiO sub 2 . Electron-transfer rates for the oxidation of ferrocene in acetonitrile at native and anodically grown TiO sub 2 films are reported and correlated with the measured SDOS of these materials. Graphs. 32 ref.--AA