Investigation of gas sensing property of zinc oxide thin films deposited by Sol-Gel method: effects of molarity and annealing temperature

Sol-Gel method has been used to deposit pure zinc oxide on glass substrates in two different conditions. The molarity was selected 0.2, 0.3 and 0.4 molar, and the annealing temperature was chosen 450 degrees C, 500 degrees C and 550 degrees C. The structural and morphological properties of the thin films have been investigated using X-ray diffraction and field emission scanning electron microscopy, and some important structural parameters of the optimized sample were determined. By using an electric circuit, their ethanol sensing features have been studied. Several related sensing parameters such as activation energy, optimal operating temperature, dynamic response, sensitivity and response/recovery times of the samples were determined and compared. An uncommon p-type sensing behavior is observed in all samples during the increase in operating temperature (at a temperature of about 370 degrees C). Considering all the sensing parameters, it seems that the sample Zn4 (0.4 molar zinc oxide with 450 degrees C annealing temperature) is optimized as a sensor.