Formation of atomically smooth terraces during cleavage of bismuth crystals; dynamics of the terrace boundaries

Scanning tunneling microscopy has been used to study a basal-plane surface of Bi formed by in situ cleavage in a vacuum of 10(-9) torr. The cleavage face has atomically smooth terraces ranging in size from a few nanometers to a few hundred nanometers. In most cases the terrace boundaries are blurred over two or three interatomic distances, even at room temperature. This blurring increases to tens of angstroms upon heating to 520-530 K. The activation energy for the motion of the boundaries can thus be estimated to be about 700 K. However, the straight boundaries oriented along atomic rows are atomically smooth at room temperature.