Abstract
A porous silicon rugate filter was prepared and investigated for its ability to sense ethanol vapors of different concentrations. The structure shows sensitivity to concentrations above 1% in volume up to saturation at room temperature. This sensitivity is in the form of a red shift of the characteristic peak of the filter due to capillary condensation phenomenon. Exposing the structure to saturated ethanol vapor produces partial filling of the pores with liquid. Theoretical calculations using the Bruggeman effective medium approximation and characteristic matrix method were employed to estimate the average volume fraction of ethanol molecules condensed into the pores. Electrochemical oxidation of the filter was performed. Furthermore, the oxidized structure was found to improve the durability of the filter and increase the adsorbed amount of ethanol molecules into the pores. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.