High-performance capacitive humidity sensor based on silicon nanoporous pillar array

A capacitive humidity sensor with coplanar interdigital electrodes was fabricated based on silicon nanoporous pillar array (Si-NPA). By applying an electrical signal of 1 kHz frequency, a capacitance increment over 1190% was obtained with the relative humidity changing from 11.3% to 94.6%. The response and recovery times were determined to be ∼ 11 s and 2 s, respectively, and the humidity hysteresis observed was small. These performances were attributed to the unique structure and morphology of Si-NPA, i.e., the nanoporous and regularly arrayed silicon pillars not only enlarged the sensing area, but also provided an effective channels for vapor transport.