Fabrication and properties of anodic alumina humidity sensor with through-hole structure

Through-hole structural humidity sensor was fabricated by radio-frequency magnetron sputtering deposition of gold electrodes on two sides of anodic aluminum oxide (AAO) membranes which were prepared by two-step anodization procedure at 0-5 degrees C and 40 V in 0.5 mol/L oxalic acid electrolyte. The investigation on the impedance at various humid conditions showed a linear relationship between impedance and relative humidity over the range of 12%-97% RH. Other excellent properties such as rapid response and good reproducibility were also obtained.