| AVS 56th International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS2-MoM |
| Session: | TiO2 Surfaces and Interfaces |
| Presenter: | N. Athavan, Portland State University |
| Authors: | N. Athavan, Portland State University V. Shutthanandan, Pacific Northwest National Laboratory P. Nachimuthu, Pacific Northwest National Laboratory S. Thevuthasan, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
TiO2 is one of the most heavily studied materials for photocatalytic water splitting even though it has a poor overlap of its optical absorption spectrum with the solar spectrum and high e-/h+ pair recombination rate. Band gap reduction is one approach to enhance visible light absorption in TiO2. Anion (N, C and S) doping causes a red shift of the absorption edge into the visible region and visible-light-induced photochemistry has been observed on these materials. Recently, we have investigated S doped TiO2(110) rutile by ion implantation as a function of substrate temperatures and dopant concentrations. Subsequently 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), Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA) and proton induced x-ray emission (PIXE) in both random and channeling directions. Depth profile of S implanted TiO2 was obtained using XPS. PIXE was used to locate the lattice sites of S while NRA and RBS were used to measure the lattice sites of oxygen and titanium atoms, respectively. PIXE measurements along the channeling and random geometries clearly demonstrate the substitution of sulfur for oxygen in TiO2 lattice under certain implantation conditions. Angular scans obtained around <110> were used to investigate the lattice site locations of sulfur at different annealing conditions. When the implanted sample is further annealed at 700oC for 1 hour at 100 Torr of oxygen, the sulfur atoms moved from the substitutional sites to interstitial sites. Subsequent annealing in vacuum (1 x10-5 Torr) at 800oC for 1 hour showed that the displaced sulfur atoms reoccupied the substitutional sites. Additional vacuum annealing at 900oC is not only retained the S atoms at the oxygen lattice sites but also improved the overall crystalline quality of the implanted region.
This work is supported by grants from DOE BES Division of Chemical Sciences and Office of Biological and Environmental Research