Characterization of thermally carbonized porous silicon humidity sensor

We report the properties of a capacitance type thermally carbonized porous silicon (TC-PS) humidity sensor at room temperature. Several constructions to use porous silicon as a miniaturized humidity sensor material have been introduced earlier. In these applications, poor long-term stability of PS is most often improved by thermal oxidation. However, thermally carbonized PS surface has been found to be at least as stable in humid atmosphere, and in addition to that, the thermal carbonization also maintains the originally large specific surface area of PS. Indeed, our sensor shows good sensitivity over a wide range of relative humidity. The repeatability is excellent but the hysteresis above 60% of relative humidity should be reduced. The effect of measurement frequency on the sensitivity is also demonstrated. (C) 2004 Elsevier B.V. All rights reserved.