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

摘要

Uniformly distributed jet of fine droplets was created with control of spray rate (S_f) 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 S_f ≤ 4.5 ml/min, above which films favored [101] direction. FE-SEM and AFM analysis revealed the uniform vertical growth of ZnO nano-rods for S_f= 2.5 ml/min and the film exhibited highest transmittance (95%) with lowest dark resistivity (~10~(-2) Ω-cm). The deposition rate increased due to rise in S_f. Alteration of crystallinity, grain size and film thickness with variation in S/lead to variation of band-gap energy from 3.198 eV to 3.302 eV. ZnO film deposited at optimal S_f= 2.5 ml/min exhibited maximum electrical conductivity σ = 78.8 Ω~(-1)-cm~(-1), minimum sheet resistance R_s = 2.04 × 10~2 Ω/□ and highest figure of merit Φ_(TC) = 2.93 × 10~(-3) Ω~(-1).