Atomic-Scale Investigation of Layered Cu₇Te₄ Nanostructures Featuring Two and Three Tellurium Layers

Copper-based chalcogenide materials exhibit unique properties that make them promising for various applications. In particular, understanding the structural diversity and transitions in Cu-rich Cu–Te phases is crucial for optimizing their performance. This study explores two distinct Cu 7 Te 4 phases consisting of 2 and 3 Te layers per nanoscale building unit using advanced methods of aberration-corrected scanning transmission electron microscopy. Cu 7 Te 4 structures exhibit distorted hexagonal close-packed Te layers, forming periodic nanoscale Cu–Te building units separated by vacancy layers. A crystal structure model for the triple-layered Cu 7 Te 4 structure is proposed based on atomic-scale images and image simulations. The Cu 7 Te 4 structures exhibit stacking defects, twin boundaries, and dislocations. A detailed structure analysis shows that the triple-layered Cu 7 Te 4 structure can form disordered configurations with Cu vacancies. Moreover, the triple-layered structure can easily be transformed into the double-layer structure through short-range atomic rearrangements of Cu atoms. Overall, these findings provide valuable insights into the atomic-scale structures and formation of the preferred phases of layered Cu–Te, expanding the structural diversity of layered chalcogenides.