| AVS 54th International Symposium | |
| Surface Science | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | P. Nachimuthu, Pacific Northwest National Laboratory |
| Authors: | P. Nachimuthu, Pacific Northwest National Laboratory S. Andrews, Pacific Northwest National Laboratory V. Shutthanandan, Pacific Northwest National Laboratory M.H. Engelhard, Pacific Northwest National Laboratory T. Tyliszczak, Lawrence Berkeley National Laboratory D.K. Shuh, Lawrence Berkeley National Laboratory S. Thevuthasan, Pacific Northwest National Laboratory M.A. Henderson, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
In semiconductor photochemistry, the redox potential of a photocatalyst is strongly modified by its band gap, which in turn dictates the energy separation of the electron-hole (e-/h+) pairs. The position of the bands relative to the band gap with respect to the electron donor and acceptor orbitals in the reactants determines the degree of overlap between adsorbate molecular orbitals and the electronic states associated with the e-/h+ pairs. TiO2 is one of a few candidate materials with promising photocatalytic properties although the optical absorption spectrum of pure TiO2 has poor overlap with the solar spectrum and high e-/h+ pair recombination rates. However, anion doping of TiO2 is known to red-shift its optical absorption spectrum into the visible region and as a result, visible light phtotoactivity has been observed for N-doped TiO2. Recently, we have investigated C-doped TiO2(110) rutile using ion beam implantation as a function of temperature and dopant concentrations. Subsequent high temperature annealing was carried out on selected samples to heal the implantation damage as well as to understand the location and mobility of the dopants in the rutile lattice. Following implantation and annealing, the samples were characterized using several surface and bulk sensitive techniques such as x-ray photoelectron spectroscopy (XPS), near-edge x-ray absorption fine structure (NEXAFS), Rutherford backscattering spectrometry (RBS) (both random and channeling), and nuclear reaction analysis (NRA). NRA measurements along the channeling and random geometries clearly indicate the substitution of carbon for oxygen in the TiO2 lattice under certain conditions. XPS data on sputter cleaned samples show the presence of carbon in two different environments with binding energies of 282.4 eV (carbide; Ti-C interaction) and 284 eV (C-C and/or C-O interactions). However, sputter cleaning followed by annealing in oxygen, eliminates the higher binding energy features suggesting that sputtering effects play a role in modifying the carbon environment in the rutile lattice. Carbon K-edge NEXAFS data are consistent with the XPS findings. Both XPS and NEXAFS show that non-carbidic interactions were significantly developed following annealing at high temperatures, although no evidence of carbon release was found from these C-doped samples.