Interfacial Step Structure at a (0001) Basal Twin in Bi2Te3

At present, little is known concerning the atomic-scale structure of grain boundaries in Bi2Te3 and related thermoelectric materials. As twins are perhaps the simplest possible type of grain boundary, they provide a good starting point for studies of interface structure in this class of materials. Here, we present an electron microscopic study of an interfacial step observed at a (0001) basal twin boundary in Bi2Te3. We discuss the crystallography of defects at twins in Bi2Te3 by considering the geometric implications for differently terminated step arrangements and comparing the defect configurations anticipated for deformation and annealing/growth twins. Finally, we consider the observed defect in this framework and discuss its relationship to analogous features in face-centered-cubic metals, namely the {112}-type interfaces that are commonly observed terminating {111} growth and annealing twins in these materials. This analysis provides insight concerning the relationships of dislocations to twin formation and morphology in Bi2Te3.