Effect of Surface Morphology on the Response Speed of Moisture Sensors

Relative humidity sensors are used for high-humidity measurement and moisture sensor or dew point sensors are used for low-humidity measurement (<1 ppmv). We fabricated moisture sensors using α-Al2O3films as porous dielectric materials deposited by anodic spark deposition. In this study, a variety number of small pores has been studied to investigate the response speed of moisture sensors. Three different surface morphologies have been studied using scanning electron microscopy. One sample has the maximum number of small pores, one sample has the medium number of small pores, and the last sample has the minimum number of small pores. Small pores are defined as pore size ranging from 40 nm to 200 nm. We found that the sensor made as porous material with the maximum number of small pores has the fastest response speed, and that from the minimum number of small pores has the slowest response speed either from high humidity to low humidity or from low humidity to high humidity.