Abstract
Zinc Oxide (ZnO) thin films were deposited on glass substrates via the spray pyrolysis technique. The films were subsequently annealed in ambient air from 300°C to 500°C. The morphology and structural properties of the thin films were studied by field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), and X-ray diffractometry (XRD) techniques. Electrical resistivity of the thin films was measured using a data acquisition unit. The optical properties of the films were characterized by UV-vis spectroscopy and photoluminescence (PL) technique. X-ray diffraction data showed that the films were grown in the (002) direction with a hexagonal wurtzite structure. The average grain size ranged from 15 to 27 nm. Increasing annealing temperatures resulted in larger grain sizes and higher crystallinity, with the surface roughness of annealed films being more than twice if compared to unannealed film. The electrical resistivity of the films decreased with the increasing annealing temperature. The UV and visible band emissions were observed in the photoluminescence spectra, due to exciton and defect-related emissions, respectively. The transmission values of the films were as high as 90% within the visible range (400–700 nm).
Highlights
Zinc Oxide (ZnO) nanomaterials are being applied in electronics, photonics, catalysis, lighting, and chemical sensing
The field emission scanning electron microscope (FESEM) micrograph shows that the unannealed films are not compact and have very small crystallites on Si substrate, which occur due to incomplete intermediate products from the spray pyrolysis technique
ZnO thin films were prepared by spray pyrolysis method, and it was thermally annealed at different temperatures
Summary
ZnO nanomaterials are being applied in electronics, photonics, catalysis, lighting, and chemical sensing. The spray pyrolysis method is one of the best methods to produce large area coatings based on the previous studies [3,4,5,6,7,8,9,10,11] It is simple, has low temperature deposition, is cost-effective, has good adhesion between films and substrate, and demonstrates uniform particle distribution, high purity, and excellent optical properties [12]. The spray pyrolysis method is efficient in producing thin film, multilayer film, thick film, and porous film on an inexpensive substrate [12] Several oxides, such as ZnO [14], CdO [15], TiO2 [16], SnO2 [17], NiO [18], and Bi2O3 [19], have been deposited using a spray pyrolysis method. The effects of annealing on the structural, morphological, electrical, optical, and photoluminescence behavior of ZnO films are investigated
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