Atomic layer epitaxy of copper: an ab initio investigation of the CuClrH process 2 III. Reaction barriers

An ab initio investigation of the energy barriers for hydrogen reduction of CuCl on copper 111.surfaces, as well as in the gas phase, has been performed in the present investigation. It is concluded that the elimination of chlorine from CuCl by the addition of H2 proceeds via surface reactions between hydrogen and CuCl both adsorbed on Cu 111.. The activation energy for the reaction between CuCl adsorbed on a threefold site.and H adsorbed on an adjacent on-top site. is only 53 kJ moly1, i.e., almost identical to the reaction energy for this surface process. However, the CuClqH surface reaction should presumably start with both species adsorbed in their preferred threefold sites. By assuming that H diffusion from threefold to top is not hindered by any barrier, the barrier energy for the most possible surface reaction is estimated to become 83 kJ moly1. This value is in close correspondence to the experimental value of 85 kJ moly1 that has been previously reported. q2000 Elsevier Science B.V. All rights reserved