Jpn. J. Appl. Phys. 18 (1979) pp. 1223-1229  |Next Article|  |Table of Contents|
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Coadsorption of Thorium and Hydrogen on a Tungsten Surface

Hyun Woo Kim and Kimio Okuno

(Received January 10, 1979)

The coadsorption of thorium and hydrogen on a tungsten surface has been investigated with a field emission microscope (FEM). When the coverage of thorium (θ_Th)is less than half a monolayer, the work function of the surface decreases with θ_Th owing to the formation of surface complexes such as WH^-Th⁺ by the adsorption of hydrogen on the Th-covered tungsten surface. The maximum decrease in work function is found to be 0.23 eV at θ_Th=θ_H=0.5, when the number of the surface complex, WH^-Th⁺, is largest. When θ_Th is larger than half a monolayer, the change in the work function (Δφ) decreases; it becomes zero at θ_Th=0.64. Thus, when θ_H=0.5, the curve for Δφ vs. θ_Th is symmetrical about the point θ_Th=0.5. When the coverage of hydrogen is larger than 0.5, Δφ also decreases owing to the increase in the number of the surface complex, Th⁺H^-, on the coadsorption surface. The sticking probability of hydrogen on a tungsten surface covered with Th is found to be 0.025 to 0.05, half that on a clean tungsten surface. When the coadsorbed surface is heated to 900∼1000 K, only the hydrogen is desorbed, with an activation energy of 2.36 eV, comparable to that on a clean tungsten surface.

URL: http://jjap.jsap.jp/link?JJAP/18/1223/
DOI: 10.1143/JJAP.18.1223

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