Atomic-scale structure and stability of the square root(31) x square root(31)R9 degrees surface of Al2O3(0001).

Through the interplay of noncontact atomic force microscopy studies and density functional theory calculations, an atomistic model for the Al2O3(0001)-square root(31) x square root(31)R9 degrees surface reconstruction is revealed. The surface is found to consist of an Al adlayer on the Al2O3 substrate, and the driving force for the formation of the reconstruction is related to a detailed balance between strain in the adlayer and the preference for Al atoms to be located on distinct substrate sites.