Facile preparation of various ZnO nanostructures via ultrasonic mist vapor deposition: a systematic investigation about the effects of growth parameters

ZnO thin films with various surface morphologies were deposited on glass substrate via a facile and well-controllable method so-called ultrasonic mist vapor deposition (UMVD). The effects of important growth parameters namely substrate temperature (T_s), nozzle-substrate distance (D) and nozzle aperture diameter (d) on optical, electrical and surface properties (both in micro and macro-scale) of synthesized thin films were carefully investigated. In case of d = 10 mm and D = 6 cm, ZnO nanoseeds and nanorods were grown at T_s = 330 and 500 °C, respectively. Interestingly, ZnO nanosheets were grown perpendicular to the substrate when d = 10 mm, D = 9 cm and T_s = 400 °C. More rough surfaces (in macroscopic scale) were grown for small D (6 and 9 cm) and lower substrate temperature (T_s = 330 and 400 °C) while for T_s = 500 °C a smooth and uniform surface can be obtained at any distance. The layer prepared with d = 10 mm, has the lowest roughness (33 nm) which is one order of magnitude lower than other samples. Increment of T_s, d and also D reduced the electrical sheet resistance. The growth mechanisms leading to obtain various morphologies for different samples were also proposed and discussed.