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

The precise mechanism governing the reversible semiconductor-to-metal transition (SMT) in V2O5 remains elusive, yet its investigation is of paramount importance due to the remarkable potential of V2O5 as a versatile "smart" material in advancing optoelectronics, plasmonics, and photonics. In this study, distinctive experimental insights into the SMT occurring in amorphous V2O5 through the application of highly sensitive, temperature-dependent, in situ analyses on a V2O5 thin film deposited on soda-lime glass are presented. The ellipsometry measurements reveal that the complete SMT occurs at approximate to 340 degrees C. Remarkably, the refractive index and extinction coefficients exhibit reversible characteristics across visible and near-infrared wavelengths, underscoring the switch-like behavior inherent to V2O5. 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 V2O5 at 320 degrees 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 V2O5. It is revealed for the first time that the SMT in V2O5 is solely contingent upon electronic state changes, independent of structural transitions, and importantly, it is a reversible transformation within the amorphous state itself. Unveiling the Mystery: The reversible semiconductor-to-metal Transition in amorphous V2O5. This study employs advanced, temperature-dependent in situ analyses, providing compelling evidence for the elusive phenomenon. Through meticulous investigation, the specific conditions triggering this transition are identified. The findings demonstrate that changes in the electronic state serve as the driving force behind the semiconductor-to-metal Transition, preserving its amorphous structure of V2O5 without necessitating any structural transformations. image