In Situ Observation of Thermally Induced Structural Transitions in Vacancy-Doped Cuprous Telluride (Cu2-xTe) Nanowires Using Raman Spectroscopy

A fundamental understanding of the thermal stability of vacancy-doped cuprous telluride nanocrystals (Cu2-xTe NCs) will be conductive to their exploitation in plasmon-related applications. However, the thermally induced structural and Raman spectral changes of Cu2-xTe NCs have remained fairly unexplored so far. Here, temperature-induced structural transitions of Cu2-xTe nanowires (NWs) are studied by in situ Raman spectroscopy from -190 to 530 degrees C. Results reveal a dramatic temperature dependence of Raman signatures of Cu2-xTe NWs, serving as a potent indicator for their structures and structural transitions. The hexagonal weissite-to-orthorhombic phase transition takes place in the cooling process from 25 degrees C to -190 degrees C. An intermediate state of high degree of disorder with featureless Raman spectra is observed before its dissociation into the elemental Cu and the high-temperature phase above 480 degrees C. This work provides fundamental insights into the thermally induced structural stability of Cu2-xTe NWs and will further stimulate new exploration of their plasmon-related practical applications.