Mesoporous Metastable CuTe₂ Semiconductor

Binary metastable semiconductor materials offer exciting possibilities in the field of optoelectronics, such as photovoltaics, tunable photosensors, and detectors. However, understanding their properties and translating them into practical applications can sometimes be challenging, owing to their thermodynamic instability. Herein, we report a temperature-controlled crystallization technique involving electrochemical deposition to produce metastable CuTe₂ thin films that can reliably function under ambient conditions. A series of in situ heating/cooling cycle tests from room temperature to 200 °C followed by spectral, morphological, and compound analyses (such as ultraviolet-visible light spectroscopy, X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS)) suggest that the seeding electrodes play a key role in the realization of the metastable phase in CuTe₂ films. In particular, CuTe₂ films deposited on Al electrodes exhibit superior crystallinity and long-term stability compared with those grown on a Au substrate. The XRD data of thermally annealed CuTe₂ thin films deposited on Al show a markedly sharp peak, indicating significantly increased crystal-domain sizes. Our method can be used to achieve the metastable phase of CuTe₂ with a bandgap of 1.67 eV and offers outstanding photoresponsivity under different illumination conditions.