Field emission study of the growth of close-packed and stepped surfaces of a tungsten single crystal

A field electron emission microscope was used for studying the vacuum deposition of tungsten. The single crystal tungsten tips, 0.8 to 1.5 μm radius, used as a substrate had perfect {110}, {112} and {100} faces, surrounded with stepped regions. Elementary processes of crystallization and atomic mobility at low substrate temperatures (140 to 750 K) were investigated. With increasing substrate temperatures the mean free path of the atoms on terraces and near steps increased, and so did the probability of overcoming the reflecting barriers first at the edges of small islands and, ultimately, also at the edges of terraces and faces. The successive appearance of each of the transfer mechanisms mentioned resulted in new types of roughness that were clearly distinguished in the experiment.