Effects of operating conditions on thin film deposition performance in air atomizing spray pyrolysis

Thin films have been finding more and more applications in electronics, optical devices, and energy conversion and storage devices, to name a few. As one of the most promising thin film deposition techniques, air atomizing spray pyrolysis, which uses compressed air to disrupt the liquid stream into droplets, has been favored in scientific and engineering communities. However, the effects of operating conditions such as liquid flow rate, atomizing air pressure, fan air pressure, and air gap on the geometric properties of deposited thin film are still not systematically studied. The objective of this study is to experimentally investigate the effects of air spraying operating conditions on the surface roughness and thickness of deposited zinc oxide (ZnO) thin film. It is found 1) The surface roughness increases with the liquid flow rate, but decreases with the atomizing air pressure, fan air pressure, and air gap; 2) The surface roughness decreases along both the X and Y directions under any given operating condition; 3) The thickness increases with the liquid flow rate and the atomizing air pressure, but decreases with the fan air pressure and the air gap; and 4) The thickness generally changes differently along the X and Y directions. Along the X direction, it decreases monotonically; however, along the Y direction, it increases first then decreases as in a saddle shape. While ZnO film deposition is studied, it is expected that the above conclusions may be applicable in air spraying other materials.