Desorption and Surface Diffusion: Nitrogen on Tungsten (110).
ILLINOIS UNIV AT URBANA-CHAMPAIGN COORDINATED SCIENCE LAB
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Scanning Auger spectroscopy has been used to monitor the migration of nitrogen atoms down a concentration gradient, on the 110 plane of tungsten. This concentration gradient is formed by the electron stimulated dissociation of molecular nitrogen, initially adsorbed at 95 K. These deposits are found to be thermally stable to several hundred K and uneffected by further electron irradiation. The adsorbed atoms form two different surface structures, depending upon the surface concentration. The desorption kinetics of both molecular and atomically bound nitrogen have been studied by a combination of Auger spectroscopy and flash desorption. The desorption of atomically bound nitrogen occurs as a second order process with an activation energy more than 7 times the activation energy of diffusion. Despite the large binding energy of the atomic nitrogen to the 110 surface, 153 kcalmole, there is virtually no change in the work function upon adsorption. In addition the saturation coverage of the irradiated atomic nitrogen is found to be more than twice that of the nitrogen adsorbed at room temperature. Both are found to be in identical binding states. Author
- Atomic and Molecular Physics and Spectroscopy