A Field Emission Microscopic Study of Hydrogen Adsorption on a Stepped Tungsten Plane: W(310)

Abstract

Using a newly developed Derivative Field Emission Current (DFEC) methods, the heat of desorption and the work-function-change of W(310) plane induced by hydrogen adsorption are measured. The average work function of the W(310) plane increases initially as the hydrogen dose increases for the low coverage region, decreases for the dose higher than about 0.7 Languimir, and saturates at about 4 Languimir. We find the eight hydrogen adsorption sites on the W(310) plane. Three of these sites are on the terrace (100) plane and the hydrogen adsorption on these sites lower the work function. The other three sites are on the step-wall (110) plane raising the work function. Last two sites are probably on the step-edge. The heats of desorption for these sites ranges from 16.6±2.0 kcal/mol for the γ2 state to 32.0±1.0 kcal/mol for the β6 state. An indirect comparison and analysis show that our findings are quite reasonable.