Formation of small straight steps among large rough steps on the {1 1 0} face of cadmium mercury thiocyanate crystal

Abstract

Rough steps generated by dislocation sources are very often observed on the {1 1 0} faces of cadmium mercury thiocyanate crystal, which is believed to result from the complex solution structures and the various growth units incorporated into the crystal lattice. Among these large rough steps, some small straight steps perpendicular to the [1 1 3 ̄ ] direction are formed. The heights of the straight steps vary from 1.6 up to 8.1 nm, most of which are multiples of the elementary step height (0.81 nm). Below each small step, there exists a hole where some impurities are adsorbed. The striking feature of these small straight steps is that they are formed by bunching of part of the rough steps, which is quite different from the usual step bunches. The occurrence of these straight steps is closely related to the slopes of growth hillocks, which is explained by the BCF theory.