An influence of deposition temperature on structural, optical and electrical properties of sprayed ZnO thin films of identical thickness

• The ZnO films exhibit highest transmittance (95%) and lowest resistivity (0.011 Ω-cm).
• Higher Ts add to grain size (31 -60 nm) which shifts the Eg (3.272 -3.242 eV).
• At higher Ts electrical conductivity rises due to desorption of chemisorbed oxygen.
• The hydrophobicity increases with rise in Ts due to growth of ZnO nanorods.

Nanocrystalline ZnO thin films were deposited at different temperatures (Ts = 325 °C–500 °C) by intermittent spray pyrolysis technique. The thickness (300 ± 10 nm) independent effect of Ts on physical properties was explored. X-Ray diffraction analysis revealed the growth of wurtzite type polycrystalline ZnO films with dominant c-axis orientation along [002] direction. The crystallite size increased (31 nm–60 nm) and optical band-gap energy decreased (3.272 eV–3.242 eV) due to rise in Ts. Scanning electron microscopic analysis of films deposited at 450 °C confirmed uniform growth of vertically aligned ZnO nanorods. The films deposited at higher Ts demonstrated increased hydrophobic behavior. These films exhibited high transmittance (>91%), low dark resistivity (∼10−2 Ω-cm), superior figure of merit (∼10−3 Ω−1) and low sheet resistance (∼102 Ω/□). The charge carrier concentration (η -/cm3) and mobility (μ – cm2V−1s−1) are primarily governed by crystallinity, grain boundary passivation and oxygen desorption effects.

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