Growth of highly porous ZnO nanostructures for carbon monoxide gas sensing

In the present work, Nanostructured ZnO sensing layers having preferred orientation along (002) plane have been grown by rf sputtering technique in glancing angle deposition (GLAD) configuration. ZnO nanostructures grown at a GLAD angle of 70 degrees exhibit sensing response of about 5.75 x 10(2) at a relatively lower operating temperature of 150 degrees C towards 500 ppm of CO gas. Afterwards the optimized ZnO sensing element has been decorated with the Pd catalyst and an enhanced CO gas sensing response of 1.022 x 10(3) has been obtained with quick response time and recovery time of 17 s and 23 s respectively. The fabricated Pd/ZnO sensing element is found to be highly selective towards detection of target CO gas. The possible sensing mechanism has been explained in detail.