Demystifying the Semiconductor‐to‐Metal Transition in Amorphous Vanadium Pentoxide: The Role of Substrate/Thin Film Interfaces

Abstract The precise mechanism governing the reversible semiconductor‐to‐metal transition (SMT) in V 2 O 5 remains elusive, yet its investigation is of paramount importance due to the remarkable potential of V 2 O 5 as a versatile “smart” material in advancing optoelectronics, plasmonics, and photonics. In this study, distinctive experimental insights into the SMT occurring in amorphous V 2 O 5 through the application of highly sensitive, temperature‐dependent, in situ analyses on a V 2 O 5 thin film deposited on soda‐lime glass are presented. The ellipsometry measurements reveal that the complete SMT occurs at ≈340 °C. Remarkably, the refractive index and extinction coefficients exhibit reversible characteristics across visible and near‐infrared wavelengths, underscoring the switch‐like behavior inherent to V 2 O 5 . The findings obtained from ellipsometry are substantiated by calorimetry and in situ secondary ion mass spectrometry analyses. In situ electron microscopy observations unveil a separation of oxidation states within V 2 O 5 at 320 °C, despite the thin film retaining its amorphous state. The comprehensive experimental investigations effectively demonstrate that alterations in electronic state can trigger the SMT in amorphous V 2 O 5 . It is revealed for the first time that the SMT in V 2 O 5 is solely contingent upon electronic state changes, independent of structural transitions, and importantly, it is a reversible transformation within the amorphous state itself.