Continuous Observation of Initial Growth and Coalescence of Bismuth Deposits by In Situ Electron Microscopy

Abstract

The vacuum deposition of bismuth on a thin substrate of molybdenum disulfide was carried out inside an electron microscope. Time sequences of the formation process of a thin film were recorded using a ciné camera. Initial growth of deposits was studied as a function of substrate temperature. It is found that the linear dimension of particles increases nearly proportionally to the square root of deposition time in the range of substrate temperatures observed. At the temperature of about 150 °C, particles having a dimension less than 150 Å, are liquid, and transformation from liquid to crystalline particles, as they grow larger, is also observed. The coalescence process of particles was recorded on ciné films at relatively higher speeds. It is found that coalesced particles have, in general, a small projected area compared to the sum of areas of initial two particles. The mechanism of this process is discussed in connection with the theory of sintering as proposed by Pashley et al. [Phil. Mag. 10, 127 (1964)].