2. GROWTH OF GOLD FILMS ON ROCKSALT IN HIGH VACUUM-GROWTH MODEL

The observed behaviour of the sticking coefficient of Au on uncontaminated (thermally etched) NaCl1) is approximated in terms of a stepped surface model which, when fitted to the experimental results, gives a step spacing of 734 Å in fair agreement with the spacings observed on electron micrographs of very thin (∼20 Å) Au films grown on such NaCl surfaces. The model was found to predict the variation of the initial sticking coefficient with temperature very closely. Electron micrographs of Au films grown on contaminated NaCl revealed no steps but randomly distributed nuclei and it is appreciated that an island model would be more suitable to explain the general behaviour but would lead to both experimental and theoretical complications. In a special case for which the latter model was investigated it predicts an average island separation of 400 Å in fair agreement with the observed value and it further predicts that in cases of contaminated NaCl, where the average separation of nuclei was observed to be of the order of 160 Å, unity sticking should result, as was observed. Possible influences of contaminants on the substrates are discussed. © 1968.