Aluminum UPD and Alloy Formation on (111)-Textured Au in AlCl{sub}3-EMImCl Ionic Liquid

摘要

The kinetics of Al-Au surface alloy formation was examined during Al underpotential deposition (upd) onto (111)-textured Au from Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl{sub}3-EMImCl) using linear sweep stripping voltammetry following potentiostatic deposition. The upd of Al on Au is a two-step process; the first step may be the reductive decomposition of AlCl{sub}4 that is known to be adsorbed on the Au surface. Following completion of the Al monolayer, two alloys are formed. The first is only present at short times and is restricted to the near surface while the second is the more stable of the two and extends into the Au substrate. The upd of Al causes a negative (compressive) change in the surface stress; however the stress change becomes tensile in the region of alloy formation. The magnitude of the tensile stress change observed experimentally is close to that calculated from the elastic strain associated with the change in molar volume and from the reaction kinetics obtained from stripping voltammetry.