Capacitive humidity sensing properties of hydrothermally-etched silicon nano-porous pillar array

Hydrothermally-etched silicon nano-porous pillar array (Si-NPPA) was studied as a sensing material to detect humidity. Room temperature capacitance sensitivity of Si-NPPA sensor was investigated at a relative humidity (RH) ranging from 11 to 95% under different signal frequencies. As a result, the measured capacitance showed an increase over 1500% at the low frequency of 100 Hz. The response time was about 15 and 5 s in RH-increasing process and RH-decreasing process, respectively. These excellent sensing characteristics indicate that Si-NPPA might be a practical sensing material.