High-resolution electron-energy-loss spectroscopy of hydrogen chemisorption at Nb(100) surfaces: Evidence for subsurface absorption sites

The interaction of hydrogen with Nb(100) surfaces has been studied by use of high-resolution electron-energy-loss spectroscopy, low-energy electron diffraction, and work-function measurements. Experimental results indicate that hydrogen absorbs on Nb(100) at tetrahedral sites below the surface. Hydrogen in these subsurface sites exhibits reversible temperature-dependent effects compatible with the self-trapped subsurface sites proposed to account for the novel kinetics of hydrogen uptake by Nb.