Effect of Film Thickness on Structural, Electrical, and Optical Properties of Sol-Gel Deposited Layer-by-layer ZnO Nanoparticles

The structural, electrical, and optical properties of layer-by-layer ZnO nanoparticles deposited using sol-gel spincoating technique were studied and now presented. Thicknesses of the thin films were varied by increasing thenumber of deposited layers. As part of our characterization process, XRD and FE-SEM were used to characterizethe structural properties, current-voltage measurements for the electrical properties, and UV-Vis spectra andphotoluminescence spectra for the optical properties of the ZnO thin films. ZnO thin films with thicknesses rangingfrom 14.2 nm to 62.7 nm were used in this work. Film with thickness of 42.7 nm gave the lowest resistivity among all,1.39×10-2 Ω·cm. Photoluminescence spectra showed two peaks which were in the UV emission centered at 380 nm,and visible emission centered at 590 nm. Optical transmittance spectra of the samples indicated that all films weretransparent (>88%) in the visible-NIR range. The optical band gap energy was estimated to be 3.21~3.26 eV, with bandgap increased with the thin film thickness.