On the nature of planar defects in transition metal diboride line compounds

Abstract

Planar defect structures appearing in transition metal diboride (TMB2) thin films, grown by different magnetron sputtering-deposition approaches over a wide compositional and elemental range, were systematically investigated. Atomically resolved scanning transmission electron microscopy (STEM) imaging, electron energy loss spectroscopy (EELS) elemental mapping, and first principles calculations have been applied to elucidate the atomic structures of the observed defects. Two distinct types of antiphase boundary (APB) defects reside on the {11¯00} planes. These defects are without (named APB-1) or with (APB-2) local deviation from stoichiometry. APB-2 defects, in turn, appear in different variants. It is found that APB-2 defects are governed by the film's composition, while APB-1 defects are endemic. The characteristic structures, interconnections, and circumstances leading to the formation of these APB-defects, together with their formation energies, are presented.