ATOMIC LAYER EPITAXY OF COPPER - AN AB-INITIO INVESTIGATION OF THE CUCL H-2 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/H-2 c opper Atomic Layer Epitaxy is presented. Adsorption of CuCl is energet ically most favourable on the two different three-fold adsorption site s with adsorption energies of 152 kJ mol(-1). Adsorption on the two-fo ld bridge site is only 10 kJ mol(-1) lower in adsorption energy than o n the three-fold sites, whereas adsorption on the on-top site is endot hermic by as much as 88 kJ mol(-1). As previously noticed in an experi mental study, adsorption is not limited by any energy barrier. The dis proportionation was investigated for three different arrangements with the composition (CuCl)(2). It was confirmed that the formation of (Cu Cl)(2) in the gas phase is favourable, but contrary to earlier experim ental findings, no indications of a disproportionation of CuCl could b e found. Adsorption of the (CuCl)(2) dimers was found to be energetica lly unfavourable implying that a dissociation to free CuCl molecules i s required prior to adsorption. (C) 1998 Elsevier Science B.V. All rig hts reserved.