Structural, Optical and Electrical Characterization of Nano-Structured ZnO Thin Films Deposited by Solution Growth Technique

Successive ionic layer adsorption and reaction technique (SILAR) and solution growth technique have been applied to deposit thin films on amorphous glass substrates. Various parameters, like concentration of complexing agent, pH of the solution, deposition temperature, time, have been optimized to achieve good quality films. Films grown by SILAR method have been found to be non-uniform as confirmed by SEM, powdery and less adherent. Films grown by solution growth method have been found to be uniform, pinhole free and well adherent. Films deposited have been characterized, i.e., structural properties by X-RD, morphological properties by SEM, optical characterization by photoluminescence (PL) and spectrophotometer, and electrical characterization (I-V characteristic and thermoelectric power) by laboratory set up. Effect of annealing has been studied. N-type conductivity of grown films has been confirmed by TEP measurement. XRD results show that the obtained films have hexagonal wurtzite phase with very good crystallinity. As-deposited ZnO film shows maximum absorption at 366 nm, and annealed sample shows maxima at 374 nm, correspondingly the band gaps are 3.29 eV and 2.9 eV. The absorbance decreases from 1.5004 to 1.0355 after annealing. PL spectra of ZnO thin films shows strong peak at 385 nm which corresponds to UV emission and a weak peak at 471 nm.