Atomic layer epitaxy of copper: an ab initio investigation of the CuCl/H2 process: I. Adsorption of CuCl on Cu(111)

An ab initio investigation of the adsorption and disproportionation of copper(I)chloride on copper(111), two crucial processes in CuCl/H2 copper Atomic Layer Epitaxy is presented. Adsorption of CuCl is energetically most favourable on the two different three-fold adsorption sites with adsorption energies of 152 kJ mol−1. Adsorption on the two-fold bridge site is only 10 kJ mol−1 lower in adsorption energy than on the three-fold sites, whereas adsorption on the on-top site is endothermic by as much as 88 kJ mol−1. As previously noticed in an experimental study, adsorption is not limited by any energy barrier. The disproportionation was investigated for three different arrangements with the composition (CuCl)2. It was confirmed that the formation of (CuCl)2 in the gas phase is favourable, but contrary to earlier experimental findings, no indications of a disproportionation of CuCl could be found. Adsorption of the (CuCl)2 dimers was found to be energetically unfavourable implying that a dissociation to free CuCl molecules is required prior to adsorption.