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Nitrogen adsorption on a W(100) surface studied by an analysis of electron energy-loss fine structure

Authors
Journal
Journal of Electron Spectroscopy and Related Phenomena
0368-2048
Publisher
Elsevier
Publication Date
Identifiers
DOI: 10.1016/s0368-2048(97)00213-2
Keywords
  • Eelfs
  • Local Surface Structure
  • Thermal Desorption Spectroscopy
  • Electron Bombardment
  • Nitrogen
  • Tungsten (100) Surface

Abstract

Abstract The influences of annealing and electron bombardment on the adsorption states of nitrogen on a W(100) surface have been investigated by an analysis of electron energy-loss fine structure (EELPS). The nitrogen K-edge EELFS were measured, and converted into radial distribution functions using the Fourier transform to obtain the atomic distance between nitrogen and tungsten. Nitrogen adsorption on a tungsten surface at 400 K induces the formation of a stableβ 2 state, and less stableβ 1 state above 0.5 ML. The nearest-neighbor inter-atomic distance drastically increases from 0.167 nm to 0.187 nm, which corresponds to distance betweenβ 2-nitrogen and tungsten in the second layer, when the surface is exposed at 0.5 ML and annealed at temperatures between 920 K and 1020 K where theβ 1-nitrogen desorbs. The temperature-dependent increase in the atomic distance means that annealing induces a lateral reconstruction of tungsten atoms in the top layer, which is reasonably interpreted with the contracted-domain structure. Bombardment of 2 keV electrons at the dose of 10 A s/cm 2 on the surface annealed at 770 K after exposing above 0.5 ML at 400 K converts some of theβ 2 state into theβ 1 state, which may result in the decrease in atomic distance between nitrogen and tungsten.

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