Temperature dependence of thermally‐carbonized porous silicon humidity sensor

Abstract

AbstractThermal carbonization of porous silicon (PS) at 820 °C under acetylene atmosphere is an appropriate method for humidity sensing purposes. It produces stable and hydrophilic surface still maintaining originally large specific surface area of PS. We report the temperature dependence of various electrical param‐ eters measured for the thermally‐carbonized PS humidity sensor. Capacitance of the sensor in dry air (6 RH%) is almost constant at various temperatures, whereas in higher relative humidity values, the temperature dependence becomes evident. The resistance variation of the sensor is less dependent on RH as the temperature increases. While the capacitance showed linear behavior as a function of temperature, the resistance had a clear non‐linear temperature dependence. In order to get information about the effects of frequency on capacitance values, we measured a phase angle and admittance of the sensor as a function of frequency at three different temperatures in low and high humidity. According to these results, it is preferable to operate this sensor construction using low frequency (<1 kHz). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)