Adsorption of hydrogen on the polar O–ZnO surface: a molecular beam study

Abstract

The interaction of atomic and molecular hydrogen with the polar oxygen-terminated ZnO(000-1) surface has been studied by He atom scattering, LEED, and He atom reflectivity measurements. Whereas the sticking coefficient S0 for molecular hydrogen is so low that only an upper limit can be given (S0 < 3 × 10−7), adsorption of atomic hydrogen leads to the formation of a H(1 × 1) adlayer. Prolonged exposure to H atoms induces a disordering of the surface. The desorption temperature of the adsorbed H atoms was determined by monitoring the reflectivity of the surface for the He atoms. Assuming that the activation energy for desorption is equal to the H atom binding energy and using a pre exponential factor of 1021 cm2/(mol s) we yield a value of 163 kJ/mol for the H atom binding energy.