Hysteresis reduction by heating the thermally-carbonized porous silicon humidity sensor

We have reduced remarkably the hysteresis on a capacitive-type thermally carbonized porous silicon (TC-PS) humidity sensor by heating the sensor during the measurement. Although the TC-PS humidity sensor has been shown to be very sensitive and quite fast, hysteresis restricts its utilization. However, by raising the sensor temperature only few degrees above ambient temperature, hysteresis can be mostly avoided. In that case, response time is also shorter. Other methods to reduce hysteresis on TC-PS humidity sensors, such as enlarging the pore size on porous silicon and tuning the surface hygroscopicity by means of the carbonization temperature, are also discussed.