The initial stages of interaction of hydrogen with the [formula omitted] surface

Abstract

The initial stages of interaction of hydrogen with a Zr(10 10) surface at 100, 293 and 370 K have been studied by nuclear reaction analysis (NRA), Auger electron spectroscopy (AES), work function measurements and static secondary ion mass spectroscopy (SSIMS). The initial sticking coefficients of hydrogen on Zr(10 10) at 100, 293 and 370 K are 1, 0.71 and 0.51 respectively. The surface concentration of hydrogen first increases rapidly with exposure and then saturates at well defined levels depending on the sample temperature. AES results indicate that the bond between hydrogen and zirconium on the surface is similar to that in zirconium hydride. SSIMS measurements have shown that there is a surface energy barrier of height 42.3 kJ/mol which prevents hydrogen diffusion from the surface into the bulk. No desorption of atomic or molecular hydrogen was detected when the H 2-exposed samples were heated in vacuum. Work function measurements indicate the presence of two types of adsorption site at the surface, one above the surface, the other being in the subsurface region, but very close to the surface. The depth of the subsurface potential well is larger than that for hydrogen adsorbed above the surface. A model is proposed to describe the processes involved in the initial stages of interaction of hydrogen with the Zr(10 10) surface.