Intermittent spray pyrolytic growth of nanocrystalline and highly oriented transparent conducting ZnO thin films: Effect of solution spray rate

[Display omitted] •ZnO films show enhancement in structural, optical and electrical properties.•Film orientation is altered from [002] to [101] direction for higher Sf>5ml/min.•Eg (eV) is influenced by variation in crystallinity, grain size and film thickness.•Nanocrystalline ZnO films are superior for TCO and optoelectronic applications.•FE-SEM and AFM study reveal growth of an array of vertically aligned ZnO nanorods. Uniformly distributed jet of fine droplets was created with control of spray rate (Sf) to deposit nanocrystalline ZnO thin films by spray pyrolysis technique. X-ray diffraction analysis indicated the polycrystalline film growth with most preferred orientation along c-axis [002] direction for Sf⩽4.5ml/min, above which films favored [101] direction. FE-SEM and AFM analysis revealed the uniform vertical growth of ZnO nano-rods for Sf=2.5ml/min and the film exhibited highest transmittance (95%) with lowest dark resistivity (∼10−2Ω-cm). The deposition rate increased due to rise in Sf. Alteration of crystallinity, grain size and film thickness with variation in Sf lead to variation of band-gap energy from 3.198eV to 3.302eV. ZnO film deposited at optimal Sf=2.5ml/min exhibited maximum electrical conductivity σ=78.8Ω−1-cm−1, minimum sheet resistance Rs=2.04×102Ω/□ and highest figure of merit ΦTC=2.93×10−3Ω−1.