On the growth of gold films on KCl in high vacuum

Abstract

Previously described experimental techniques 1,2) were employed to measure the sticking coefficient of gold on KCl single crystals under various experimental conditions. The topography of the KCl substrates and the characteristics of the gold films were investigated by transmission electron diffraction and electron microscopy. The results are compared with those previously reported for the gold-rocksalt system 1,2). At 300 °C the initial sticking coefficient is about two-thirds on uncontaminated (thermally etched) KCl and the resultant gold films were polycrystalline. The gold films were however considerably better single crystals than gold films grown on uncontaminated NaCl substrates for which a sticking coefficient of only one-third was observed 1,2). On air-contaminated KCl the sticking coefficient is unity as for air-contaminated NaCl and the resultant gold films are perfectly epitaxial. Thin gold deposits grown separately on etched and unetched KCl substrates revealed a considerable difference in their numbers of nuclei per unit area in correspondence with the difference observed between etched and unetched NaCl substrates. The results indicate that a relatively high sticking coefficient generally accompanies epitaxial growth although the reverse is not true in general. Relatively small quantities of desorbed gases could be detected from an air-contaminated sample of KCl powder employing the same technique which yielded considerable gas evolution from an NaCl powder sample.