Probing the local environment of two-dimensional ordered vacancy structures in Ga_2SeTe_2 via aberration-corrected electron microscopy

摘要

There has been considerable interest in chalcogenide alloys with high concentrations of native vacancies that lead to properties desirable for thermoelectric and phase-change materials. Recently, vacancy ordering has been identified as the mechanism for metal-insulator transitions observed in GeSb_2Te_4 and an unexpectedly low thermal conductivity in Ga_2Te_3. Here, we report the direct observation of vacancy ordering in Ga_2SeTe_2 utilizing aberration-corrected electron microscopy. Images reveal a cation-anion dumbbell inversion associated with the accommodation of vacancy ordering across the entire crystal. The result is a striking example of the interplay between native defects and local structure.