ADSORPTION AND DESORPTION-KINETICS FOR HYDROGEN ON MODIFIED ALUMINUM (110) SURFACES

Aluminum exhibits a large barrier of perhaps 1 eV to hydrogen dissocia tion. We have investigated the possibility of changing this barrier by various modifications of the aluminum surface. Pre-adsorbed oxygen do es not alter the barrier significantly, potassium increases the barrie r to some extent, whereas the evaporation of molybdenum atoms onto the aluminum surface generates sites with negligible barrier height to di ssociation. In addition, we have observed changes in the sticking coef ficient for atomic hydrogen on the modified aluminum surfaces: pre-ads orbed oxygen, for example, significantly reduces sticking.