Electrical properties of ZnO thin films prepared by sol-gel technique

Zinc Oxide (ZnO) thin films were deposited on a glass substrate by sol-gel process dip-coating method. Zinc acetate dehydrate Zn(O₂ CCH₃)₂(H₂O)₂ are used as a starting material while 2-methoxyethanol (C₃H₈O₂) and monoethanolamine (MEA) are used as a solvent and stabilizer. The molar ratio of zinc acetate dihydrate to MEA is 1:1. The molarity of the solution and pre-heating temperature were kept constant at 0.4M and 150°C. Annealing temperature was fixed at 550°C but the withdrawal speed was varied from 1 mm/s to 9 mm/s. The effects of withdrawal speed on electrical and surface morphology of the ZnO thin films have been investigated. The electrical and surface morphology properties of the ZnO thin films were characterized by I-V measurement and atomic force microscopy (AFM). The electrical measurement showed that current decrease when the withdrawal speed increases. High conductivity at 5.87×10^-4 S/cm and lowest resistivity about 1.7×10³ Ω/cm have been obtained for 1 mm/s withdrawal speed. AFM micrographs showed average grain size of ZnO thin films increases from 120.862 nm to 138.521 nm with an increasing in withdrawal speed.