Study of Molarity Concentration Variation Over Optical, Structural and Gas Sensing Response for ZnO Thin Film Based NOx Gas Sensor

Abstract

Zinc oxide (ZnO) thin films as sensing layer with different molarity concentration are obtained by the sol–gel method using spin coating technique. Zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was taken as starting material. For desired molarity weighed Zinc Acetated dihydrate is dissolved in particular amount of Ethanol. The solution is put on hot plate with Magnetic stirrer at a temperature of 60 °C while stirring 400 rpm to 600 rpm procedure continued for 45 min to 60 min. After that the solution was kept at room temperature for 24 h for ageing effect. By using spin coating method the prepared solution was coated on silicon substrate and then annealed for preparing highly crystalline ZnO thin films. The optical surface morphological and structural studies were done for the synthesized ZnO thin films. The important parameter considered for the gas sensing behavior are operating temperature and sensor response The reported study provides a significant development towards ZnO thin film thickness variations with a very high sensitivity, rapid response and recovery times. The UV–Vis transmittance spectra of ZnO thin films has been studied over quartz substrate under similar deposition parameters. The single coated samples were prepared with different molarities of 1 M, 0.7 M, 0.5 M, 0.33 M, 0.1 M, 0.05 M. Energy band gap of each sample is calculated by using Tauc plot and studied for the varying band gap & the gas sensitivity for the samples.