Influence of Ce–W co-doping on phase transition temperature of VO2 thin films deposited by ultrasonic nebulized spray pyrolysis of aqueous combustion mixture

Abstract

Vanadium dioxide is widely explored as a viable material for switching applications and a robust progress has been achieved on laboratory-scale. To realise its commercialisation, industrially-viable synthetic techniques are highly required. Ultrasonic nebulised spray pyrolysis of aqueous combustion mixture (UNSPACM) is a simple, low-cost and scalable technique which offers high quality films for various energy applications. Herein, we report synthesis, characterization and influence of Ce–W co-doping on phase transition temperature of VO2(M1) thin films deposited on quartz substrates at 350 °C by this technique. The phase was verified by x-ray diffraction and Raman spectroscopic studies. FTIR studies at 2.5 µm to 14 µm IR frequencies showed 63% reversible reflectance change of the films from low reflectivity below 60 °C to high reflectivity above 60 °C. Electrical resistance measurements on the thin films showed a first order transition with resistance change of three orders of magnitude. Ce-doping (2 atomic% of Ce) resulted in increase in reflectance (up to 72%) and transition temperature (up to 75 °C) while retaining strength of the transition. Ce–W co-doping lowered transition temperature (up to 67 °C) and reflectance (up to 45%) while retaining the transition strength. Ce–W co-doping also reduced surface roughness of the films up to rms roughness value of 36 ± 0.7 nm. We believe this technique provides an easy and simple means to synthesize VO2 thin films on large-scale for multiple applications such as smart windows among others.