Abstract: Based on the independent ultrasonic atomised pyrolytic spraying device, an electrostatic field coupling is carried out by applying non-uniform electric field between the upper and lower walls of the reactive deposition chamber. Then, the effect of applied DC voltage on the structure and properties of the sprayed TiO₂ thin film was conducted. Upon the action of the electric field, the droplet particles are polarized and gain momentum perpendicular to the substrate surface. The Coulomb force produced by electric field cancels the influence of the thermophoresis force, and then improves the adhesion efficiency of titanium precursor on the near surface of the substrate. Thus, the crystallization property and film formation uniformity of the film is greatly enhanced. The results show that when the applied voltage is 1.0 kV, the anatase TiO₂ thin film is optimized. Its (101) crystal plane has a full width at half maximum of 0.29°, an average grain size of 94.19 nm, an average visible light transmittance of 85% and a surface roughness of 16.70 nm. By applying electrostatic fields, the momentum of incident particles near the surface of the substrate is regulated and a stable environment more conducive to the growth of TiO₂ thin film is constructed. This work provides a reference for the optimization of TiO₂ thin film preparation process.

Key words: TiO₂ thin film, ultrasonic atomised pyrolytic spraying, thermophoresis force, electrostatic field, crystal growth