Electrical Switching in Semiconductor-Metal Self-Assembled VO₂ Disordered Metamaterial Coatings

As a strongly correlated metal oxide, VO₂ inspires several highly technological applications. The challenging reliable wafer-scale synthesis of high quality polycrystalline VO₂ coatings is demonstrated on 4" Si taking advantage of the oxidative sintering of chemically vapor deposited VO₂ films. This approach results in films with a semiconductor-metal transition (SMT) quality approaching that of the epitaxial counterpart. SMT occurs with an abrupt electrical resistivity change exceeding three orders of magnitude with a narrow hysteresis width. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO₂ disordered metamaterial, compresing monoclinic (M1 and M2) and rutile (R) domains, at the transition temperature region. The M2 mediation of the M1-R transition is spatially confined and related to the localized strain-stabilization of the M2 phase. The presence of the M2 phase is supposed to play a role as a minor semiconducting phase far above the SMT temperature. In terms of application, we show that the VO₂ disordered self-assembly of M and R phases is highly stable and can be thermally triggered with high precision using short heating or cooling pulses with adjusted strengths. Such a control enables an accurate and tunable thermal control of the electrical switching.