Epitaxial Growth and Structural Characterization of PbTe Thin Films on CdTe(211)B: Evidence of a 180° Twisted Interface

We report on the epitaxial growth of PbTe thin films on CdTe(211)-B substrates by molecular beam epitaxy and identify a unique interfacial relationship characterized by a 180° rotational offset about the [111] axis. High-resolution X-ray diffraction shows that PbTe films grown on CdTe(211)B do not exhibit coherent film peaks along the surface normal. Instead, pole figure analysis reveals emergent diffraction peaks aligned with the [111] axis but rotated 180° relative to the substrate. Complementary 2θ-ω scans confirm that these peaks are independent of the substrate, establishing that the PbTe films are single crystalline and that the rotational offset originates at the interface rather than from twinning. Scanning electron microscopy indicates island-like nucleation with faceted depressions consistent with (111) planes in the thinnest films and improved coverage with thickness, while atomic force microscopy shows a thickness-dependent decrease in RMS roughness and facet angles consistent with growth along the [111] direction. These findings demonstrate the presence of a twisted interface in PbTe/CdTe(211)B heterostructures, broadening the understanding of PbTe on single-crystal CdTe heteroepitaxy beyond the more commonly studied (001) and (111) orientations. The identification of this rotationally offset growth mode provides a foundation for exploring orientation-driven electronic and phonon phenomena with potential applications in thermoelectrics and CdTe-based optoelectronics.