Exposed: investigation of oxidation in selenium-tellurium evaporation materials and its effect on optoelectronic devices.

Selenium-tellurium (Se-Te) alloys have attracted sustained research interest due to their combination of photoconductive, thermoelectric, and phase-change properties, which make them promising candidates for a wide range of optoelectronic and energy-conversion applications. However, the long-term stability of Se-Te alloys, especially in bulk, has received little attention. In this work, degradation of Se-Te evaporation materials and its effects on thin-film and device behavior were investigated. Comparative analyses were conducted between Se-Te evaporation pellets stored under ambient conditions for four years and freshly prepared pellets preserved under inert atmosphere. Scanning electron microscopy (SEM) revealed that prolonged atmospheric exposure led to the formation of surface protrusions and crystalline features. Energy-dispersive X-ray spectroscopy and X-ray diffraction indicated surface crystallization and the formation of oxygen-containing phases, consistent with amorphous oxides and trigonal Se. Accelerated environmental aging of new pellets under elevated humidity and temperature replicated similar surface defects, confirming crystallization and oxidation as the dominant degradation pathway. X-ray photoelectron spectroscopy revealed Supplementary Information: The online version contains supplementary material available at 10.1007/s10854-026-17574-5.