Interface‐Driven Thermoelectric Switching Performance of VO+‐Diffused Soda‐Lime Glass

Strongly confined NaVO+ segregation and its thermoresponsive functionality at the interface between simple sputter‐deposited amorphous vanadium oxide thin films and soda‐lime glass is substantiated in this work by in situ temperature‐controlled time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS). The obtained ToF‐SIMS depth profiles provide unambiguous evidence for a reversible transformation that causes systematic switching of the NaVO+/Na+ and Na+/VO+ intensities upon cycling the temperature between 25 and 340 °C. Subsequently, NaVO complexes are found to be reversibly formed (at 300 °C) in vanadium oxide‐diffused glass, leading to thermoresponsive electrical behavior of the thin‐film glass system. This new segregation and diffusion‐dependent multifunctionality of NaVO+ point toward applications as an advanced material for thermoelectrical/optical switches, in smart windows or in thermal sensors. The conceptual design of a “thermodynamically confined ionic (NaVO+) interface/segregation layer” is demonstrated. Interface confinement via a solid‐state thermal reaction of vanadium pentoxide with sodium ions is shown. Reversible variation of electrical conductivity as a function of temperature is observed. The conjugation of VO+ with Na+ to form NaVO+ in the glass evidences semiconducting‐to‐metal transition of vanadium oxide via metal−metal interactions.