The growth of gold films on rocksalt in high vacuum

Abstract

A vacuum microbalance with a sensitivity of greater than 10 −7 g and a capacity of 500 mg was used to measure the sticking coefficient of gold on NaCl single crystals under various experimental conditions. At 300°C the initial coefficient is about one-third on clean NaCl and unity on air-contamined NaCl. The NaCl crystals were cleaned by thermal etching in high vacuum. The effect of substrate temperature on the sticking coefficient on clean NaCl was investigated. The coefficient approaches unity at about room temperature and becomes very small at temperatures above 400°C. The NaCl substrates and the Au films were investigated by optical microscopy, X-ray diffraction and electron microscopy. Clean substrates yielded polycrystalline Au films while contaminated substrates yielded single crystal Au films. An Omegatron residual gas analyzer was used for monitoring the gases desorbed from contaminated NaCl powder and these were mainly of mass numbers 18 (H 2O), 28 (CO, N 2) and 44 (CO 2).