ATOMICALLY FLAT GOLD-FILMS GROWN ON HOT GLASS

The results of a scanning tunneling microscope (STM) study of the morphology of Au films thermally evaporated onto heated glass substrates are presented. Au films of thickness 20-80 nm were evaporated onto Coming glass cover slips at temperatures of 20-465-degrees-C. Before the evaporation, the glass substrates were prebaked at 300-400-degrees-C for 12 h to remove surface contamination. Grain size and surface roughness of the films have been measured, and the best results were obtained with Au films 80 nm thick evaporated onto 300-degrees-C substrates. These films have 250-nm-diam grains with large, atomically flat tops exhibiting step-free terraces as large as 200 X 200 nm2. These results are comparable to the best reported results for Au grown on heated mica and show that epitaxial growth is not required for the production of films with large atomically flat regions. This study of Au on glass was motivated by failed attempts to produce flat films of gold on mica using recipes in the literature. Possible reasons for the poor results with mica are discussed.