In situ insight into thermally-induced reversible transitions of the crystal structure and photoluminescence properties in a Cu2Te nanoplate

Abstract

Fully understanding the temperature-induced crystal structure transition of Cu₂Te is beneficial to the design of high-performance devices based on Cu₂Te. In this study, through in situ high-resolution TEM, the crystal structure transition dynamics and mechanism of a Cu₂Te nanoplate under the action of a thermal field were studied. It is found that the reversible phase transition of Cu₂Te from the α phase to the δ phase occurs in the cycling temperature range of 25 °C–325 °C–25 °C. In a continuous thermal field at a higher temperature of 575 °C, the phase transition of Cu₂Te from the δ phase to the ε phase gradually occurs. It is found that δ-Cu₂Te and ε-Cu₂Te have the orientation relationship of (20)_δ-phase//(02)_ε-phase and [0001]_δ-phase//[111]_ε-phase. In situ Raman spectroscopy of Cu₂Te confirms the reversible phase transition. Furthermore, the photoluminescence properties of Cu₂Te at different temperatures were investigated by in situ photoluminescence experiments, in which the Cu₂Te nanoplate shows bright and reversible green emission during the heating cycle. This study not only provides a fundamental understanding of the phase transition of copper telluride, but also paves the way for the optimization of high-performance devices based on copper telluride.