Effect of solution molarity on the structural, optical, electrical and photo-response properties of SILAR-deposited ZnO films

Cost effective SILAR method was employed to deposit ZnO thin films on glass substrates for thin film UV photodetector applications. The dependence of the film properties such as structure, morphology, optical and electrical properties on the cationic precursor molarity is investigated in detail. When the solution molarity was increased from 0.1 M to 0.2 M, the crystallite size was found to increase by 270%. It was noted that the films had nearly stoichiometric composition. The SEM images revealed the presence of rod or needle-like structures in the films. The optical energy band gap of the films is slightly modified while the PL spectra showed reduced defect states and enhanced UV emission at higher molarities. The samples responded strongly to wavelengths in the near ultraviolet region. A 1400 times increase was observed in the current upon the UV illumination. The films exhibited persistent photocurrent.