Investigation of the surface morphology of thermally evaporated thin gold films on mica, glass, silicon and calcium fluoride substrates by scanning tunneling microscopy

The surface morphologies of thin gold films thermally evaporated on glass, mica, CaF2 and Si substrates were investigated by scanning tunneling micros copy (STM) and compared to each other. The surface roughness of the gold fi lms and average area of the grains observed was investigated as a function of the temperature and length of time of prebake of the substrates. The dep endence of the gold surface roughness on substrate temperature is discussed . For substrates held at room temperature the ionic interaction between gol d particles and substrate surface determines the size of the grains. Large flat areas of dimensions of the order of 200 X 200 nm(2) are obtained for 8 0 nm thick films grown on glass heated at 300 degrees C for 6 h and areas f lat over a macroscopic distance greater than 500 nm are obtained on mica he ated at 400 degrees C for the same period of time. For CaF2 gold epitaxial growth starts to occur above 200 degrees C. Epitaxial growth of fee metals on alkaline halides is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.