Development of stepped surface regions on polycrystalline gold. Low energy electron diffraction and auger studies

An initially polycrystalline gold surface, which by LEED showed no evidence of atomic order, developed diffraction patterns on argon ion-bombardment and thermal treatment at 600 K. These patterns were initially complex but became simpler. The only impurity present (AES), was calcium at a concentration of ∼20% of a monolayer, which had segregated to the surface during thermal treatment. We interpret the LEED patterns as stepped (111) surfaces possibly stabilised by calcium and put forward arguments rejecting an overlayer model. The possible potential of LEED in studying real catalysts is illustrated.