Thickness effect of nanostructured ZnO thin films prepared by spray method on structural, morphological and optical properties

• Investigation of spray time effect on surface roughness films.
• Determination growth modes considering the spray time.
• Study the effect of thickness on the optical properties

In this study, nanostructure zinc oxide (ZnO) films with different thicknesses were sprayed on glass substrates by controlling deposition time. Morphology and roughness of the films were investigated with scanning electron and atomic force microscopes as well as X-ray diffractometer. Considering with structure and surface roughness, two different growth modes as a function of spray time were determined: lateral and vertical modes which were illustrated schematically. Optical properties including photoluminescence, transmission, optical band gap and refractive index as a function of film's thickness and structure were studied. It was observed that the average transmittance is more than 80% in the visible region. With increasing deposition time, the optical band gap decreased from 3.22 to 3.19 eV. Photoluminescence spectra at room temperature showed an ultraviolet sharp emission related to band gap and a broad visible emission related to defects.

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