Fabrication and Optical Characterization of VO₂-Based Thin Films Deposited on Practical Float Glass by Magnetron Sputtering and Professional Annealing

In this paper, VO₂ thin films with good optical properties are fabricated on practical float glass by magnetron sputtering and a professional annealing method. The near-infrared switching efficiency (NIRSE) of the prepared film reaches 39% (@2000 nm), and its near-infrared energy modulation ability (ΔT_ir) reaches 10.9% (780-2500 nm). Further, the highest integral visible transmittance T_lum is 63%. The proposed method exhibits good reproducibility and does not cause any heat damage to the magnetron sputtering machine. The crystalline structure of the VO₂ film is characterized by X-ray diffraction (XRD). The lattice planes (011) and (-211) grow preferentially (JCPDS 65-2358), and a large number of NaV₂O₅ crystals are detected simultaneously. The microstructures are characterized by scanning electron microscopy (SEM), and a large number of long sheet crystals are identified. The phase transition temperature is significantly reduced by an appropriate W doping concentration (T_c = 29 °C), whereas excessive W doping causes distortion of the thermal hysteresis loop and a reduction in the NIRSE. Oxygen vacancies are created by low pressure annealing, due to which the phase transition temperature of VO₂ film decreases by 8 °C. The addition of an intermediate SiO₂ layer can prevent the diffusion of Na⁺ ions and affect the preparation process of the VO₂ thin film.