Effect of precursor concentration and sintering on functional properties of ZnO thin films deposited by aerosol-assisted chemical vapour deposition (AACVD)

ZnO thin films were synthesized from precursors of different concentrations via aerosol assisted chemical vapour deposition (AACVD) on glass substrates at 400 °C and were sintered in vacuum at 500°C. The effect of the precursor concentration and vacuum sintering on the film growth and optoelectronic properties was investigated. With the precursor concentration increasing, the films grew preferentially along the (002) plane at 0.1 M precursor and then became fully polycrystalline. From images of scanning electron microscopy (SEM), it can be observed that the grain size became larger but simultaneously the particles were physically separate. The lowest electrical resistivity (6.38 Ωcm) was gained at films of (002) preferred orientation and the optical transparency in the visible light range was as high as 82.5%. After sintering, the resistivity of both 0.05 and 0.1 M thin films decreased to 19.04 and 2.28 Ωcm, respectively whist the transparency almost remained unchanged. The improvement of electrical property could be attributed to the better crystallinity and the enlarged grain size, which significantly reduced the scattering of grain boundaries to free electrons.