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

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 alpha phase to the delta phase occurs in the cycling temperature range of 25 degrees C-325 degrees C-25 degrees C. In a continuous thermal field at a higher temperature of 575 degrees C, the phase transition of Cu2Te from the delta phase to the epsilon phase gradually occurs. It is found that delta-Cu2Te and epsilon-Cu2Te have the orientation relationship of (2110)(delta-phase)//(022)(epsilon-phase) and [0001](delta-phase)//[111](epsilon-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.