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We study the interaction of liquid organic solvents within the pores of n- and p-type porous silicon (PSi) interfaces. Several polar (acetone, methanol, ethanol, isopropanol, and water), borderline (chloroform), and nonpolar (toluene and isoprene) molecular solvents have been characterized on distinct n- and p-type pore structures, as analyzed using scanning electron microscopy. Fundamental to these studies has been the generation of Nyquist diagrams comparing the behavior for both dry and solvent treated interfaces for each system studied. The results of these studies on an undecorated PSi interface suggest a closer correlation with the dipole moments associated with the applied organic solvents rather than their dielectric response. This is supported by the observed interaction of the considered solvents with metal oxide (Au x O (x ≫ 1) and SnO x ) decorated PSi interfaces where nanostructured metal oxide-solvent dipole–dipole interactions appear to be manifest. In correlation with the Nyquist plots and the establishment of equivalent circuit models, we evaluate the real-time capacitance and conductance. These studies suggest the viability of array-based sensing for the considered organic solvents.

A simple MEMS/NEMS platform facilitates the modeling of the interaction of nanostructured metal oxide decorated porous silicon interface with gas phase analytes. These conductometric sensors operate at room temperature and atmospheric pressure, and are simple to construct. Nanostructured metal oxide deposition provides a matrix of responses to various gas species, facilitating the extraction of ambient gas concentrations from the sensor response. The sensors are simulated using a combination diffusion-interaction model that considers adsorption and electronic Fermi distribution dominated responses. The sensor simulation model provides insight into the interaction mechanisms that occur between the gas analyte and porous silicon sensor interface. Ambient gas concentrations are extracted from the sensor response through an analysis of the time derivatives of the response and an application of the nanostructured metal oxide deposition sensitivity matrix.

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