title: EUV-induced oxidation of carbon on TiO2.
abstract: Previously we reported estimates of the maximum etch rates of C on TiO2by oxidizers including NO, O3and H2O2when irradiated by a spatially-non-uniform beam of extreme ultraviolet (EUV) radiation at 13.5 nm (Faradzhev et al., 2013). Here we extend that work by presenting temporally and spatially resolved measurements of the C etching by these oxidizers as a function of EUV intensity in the range (0.3 to 3) mW/mm2[(0.2 to 2) × 1016photons s-1cm-2]. We find that the rates for NO scale linearly with intensity and are smaller than those for O3, which exhibit a weak, sub-linear intensity dependence in this range. We demonstrate that these behaviors are consistent with adsorption of the oxidizing precursor on the C surface followed by a photon-stimulated reaction resulting in volatile C-containing products. The kinetics of photon-induced C etching by hydrogen peroxide, however, appear to be more complex. The spatially resolved measurements reveal that C removal by H2O2begins at the edges of the C spot, where the light intensity is the lowest, and proceeds toward the center of the spot. This localization of the reaction may occur because hydroxyl radicals are produced efficiently on the catalytically active TiO2surface.
authors.affiliation: National Institute of Standards and Technology Gaithersburg, MD 20899, USA.
authors.forename: Nadir S
authors.initials: NS
authors.lastname: Faradzhev
authors.affiliation: National Institute of Standards and Technology Gaithersburg, MD 20899, USA.
authors.forename: Shannon B
authors.initials: SB
authors.lastname: Hill
keywords: Carbon etching; Extreme ultraviolet; Hydrogen peroxide; Photo-oxidation; Strong oxidizer; TiO2