Optimization of porous anodic alumina nanostructure for ultra high sensitive humidity sensor

• In this report, we optimize the PAA layer for humidity sensing application using two step anodization method.
• The sensitivity of the sensor reaches up-to 793.02% which is exceptionally high compared to the reported sensitivity of conventional sensor.
• An equivalent electrical circuit is proposed to represent the electrical performance at different humidity level and it is in good agreement with the observed results.

In this report, we are going to present the development and optimization of high-performance porous alumina growth having a large surface to volume ratio for ultra-high sensitive humidity sensing. The control of the structure of pores, such as the diameter of pores, depth of porous layer, etc., has shown crucial implications for the sensitivity of sensor; and there are precisely fine-tuned with the anodization process parameters. The sensitivity of the prepared sensors reaches upto 793.02% while reported sensitivity for conventional capacitive humidity sensors is much less. Besides, the prepared sensor maintains its fair responsivity as well as sensitivity even up to 100 KHz unlike 10 KHz reported by other researchers so far; and it gives an added advantage for its applications where humidity measurement at high frequencies are required The samples are characterized by Field Emission Scanning Electron Microscopy (FESEM, FEI NNS 450) to support the results and impedance spectroscopy were employed for the electrical characterization of the sensor. An equivalent electrical circuit is obtained to represent the electrical performance at different humidity level and it is in good agreement with the observed results.