General Approach to the Formation of Sensitive, Selective, Rapidly Responding Conductometric Sensors

Rapidly responding, reversible, sensitive, and selective porous silicon-based gas sensors are formed with a highly efficient electrical contact to a nanopore covered microporous array. A general approach to facilitate significant changes in sensor surface sensitivity for a variety of gases, based on a complementary concept to that of hard and soft acid and base (HSAB) interactions and commensurate with a basis in physisorption has now been formulated to create highly selective surface coatings at the nanoscale. The technology, implemented on ``phase matched'' nanoporous silicon layers positioned on porous silicon micropores facilitates the application of nanostructured metals, metal oxides, and nanoparticle catalytic coatings, and provides for notably higher sensitivities and selectivity verses, for example, metal oxide systems. Nanomaterials are applied to the PS surface to provide for the detection of gases including NO, NO$_{2}$, CO, NH$_{3}$, PH$_{3}$, SO$_{2}$, H$_{2}$S, and HCl in an array-based format at the sub-ppm level. The value of this sensor technology results from (1) sensitivity and short recovery time, (2) operation at room temperature with an insensitivity to temperature drift, (3) ease of coating with diversity of clearly mapped gas-selective materials to form sensor arrays, (5) its low cost of fabrication.