Enhanced relative humidity sensing property of porous Al:ZnO thin films

Abstract High responsive, reliable and low-cost positive type relative humidity (RH) sensors have been fabricated with aluminium (Al) doped zinc oxide (AZO) thin films synthesized by nebulized spray pyrolysis technique. The Al doping concentration in the material is varied from 1 to 5 at.%. The resistive humidity responses of the samples are measured in the range of 22–90% of RH with respect to the base humidity level 10%. Maximum responsivity of 820% is observed for 5 at.% AZO thin film at 90% RH. The sensing mechanism and the positive humidity change are explained on the ground of surface porosity and water adsorption process.