Statistical analysis of adsorbates

Abstract Now that it is possible to observe individual atoms and molecules adsorbed on a surface, a method is required to evaluate the correlation between the occupancy of neighbouring sites. To meet this need, a rigorous theoretical analysis of the distribution of adsorbates on surface sites has been developed, first for uncorrelated adsorption, and then for cases where the occupation of a site affects the probability of occupation of a neighbouring site. Statistical parameters can be measured from experimental images and related directly to the theoretical model, with allowance being made for defects and edge effects. By analysing scanning tunnelling microscope images in this way, it is found that trimethylgallium on GaAs(001)-(2 × 4) exhibits enhanced nearest neighbour occupation, whereas ethylene on Si(001)-(2 × 1) shows nearest neighbour repulsion.