Oxygen adsorption on the tungsten (110) plane. Electron impact and thermal desorption at high temperatures |
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Authors: | Ch. Steinbrüchel R. Gomer |
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Affiliation: | (1) The James Franck Institute and Department of Chemistry, The University of Chicago, 60637 Chicago, IL, USA;(2) Present address: Chemistry Division, Argonne National Laboratory, 60439 Argonne, Illinois, USA |
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Abstract: | When a layer of oxygen on the (110) plane of tungsten at coverages O/W≦0.5 is heated from 100 K, O+ evolution under electron impact becomes almost negligible at 600 K. On further heating, however, a slow, temperature-dependent evolution of O+ current is observed atT≳1500 K. For O/W>0.3 there is also desorption under massive bombardment. Once an equilibrium value of O+ current has been established, there is rapid adjustment to the appropriate equilibrium value when the temperature changes in the range 1500–1700 K. On cooling toT<1000 K, O+ decreases rapidly; on reheating toT>1500 K, O+ increases slowly again. Above 1700 K there is thermal desorption which is also reflected in the O+ signal. These facts indicate that there is a slow activated evolution of an electron sensitive state above 1500 K, from a reconstructed state formed by heating the low temperature layer toT≧1000 K. The latter state seems to be reformed on cooling below 1500 K. |
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Keywords: | 82.65 |
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