  Epitaxial films of bismuth telluride topological insulators have received
increasing attention due to potential applications in spintronic and quantum
computation. One of the most important properties of epitaxial films is the
presence of interface defects due to lateral lattice mismatch since
electrically active defects can drastically compromise device performance. By
describing hybrid reflections in hexagonal bismuth telluride films on cubic
substrates, in-plane lattice mismatches were characterized with accuracy at
least 20 times better than using other X-ray diffraction methods, providing
clear evidence of 0.007\% lateral lattice mismatch, consistent with stress
relaxation associated with van der Waals gaps in the film structure.
