CREATION OF VARIABLE CONCENTRATIONS OF DEFECTS ON TIO2,(110) USING LOW-DENSITY ELECTRON-BEAMS

Low density (similar to mu A/cm(2)) 0.48 and 1.0 keV electron beams ha ve been used to create surface defects on a TiO2(110) surface. These e lectron-beam induced defects were examined primarily by X-ray photoele ctron spectroscopy (XPS) with supporting ultraviolet photoemission spe ctroscopy (WS). Glancing and normal emission XPS spectra of nearly def ect-free surfaces revealed that Ti atoms on the surface were similar t o the bulk Ti, while some surface oxygen atoms were different from the bulk oxygen. XPS of Ti 2p(3/2) was used to quantify the defect concen tration and to examine the defect electronic structure. Based on our c alculation of defect concentrations and the comparison of our results with results and models from the literature, we conclude that oxygen v acancies induced by election beams in the current study are mostly fro m the bridging oxygen sites, in agreement with the previous work. A ra nge of defect concentrations with similar electronic structure, mainly composed of Ti3+, have been induced by low-density electron beams. Be am energy and exposure were the experimental variables. The rates of d efect formation at low beam exposure were beam-energy dependent, with a faster growth rate at 0.48 keV than at 1.0 keV. These defects were s imilar to those by thermal annealing in vacuum, but a higher concentra tion of defects could be obtained with longer beam exposure. However, the e-beam induced defects were different from those produced by Ar+ i on bombardment since both this and previous studies have found defects produced by Ar+ ion bombardment to be complex, with a variety of diff erent local environments where oxygen and titanium surface atoms coexi st.