Investigation on Gas Sensing Characteristics of Textured ZnO Thin Films Grown by Wet Chemical Synthesis

Low cost and highly sensitive hydrogen gas sensors are of great demand in various sectors owing to the flammable and explosive nature of hydrogen gas. In the present work we have synthesized highly textured, nano-crystalline wurtzite ZnO thin films using a cost effective wet chemical synthesis route and systematically investigated the hydrogen sensing characteristics of the synthesized films oriented strongly along (002) crystalline plane. ZnO thin films have been grown by spin coating the precursor sol on quartz substrates. The phase formation behavior and the microstructure evolution of the films are studied using X-ray diffraction pattern and electron microscopy analyses respectively. Using a dynamic flow gas sensing set-up, the hydrogen sensing characteristics (response%, response time, recovery time, activation energy for adsorption/desorption of gas molecules) of the synthesized ZnO thin film based sensing elements are investigated by varying the sensor operating temperature. An attempt has also been made to correlate the sensing characteristics of the grown ZnO films with their crystallographic orientation.