A capacitance-type chemical sensor that employs VAPO-5, MnAPO-5 and MAPO-36 molecular sieves as the dielectric phase

We have developed a chemical sensor based on a capacitor design that utilizes molecular sieves as the dielectric phase. In this study, thin films of vanadium aluminum phosphate (VAPO-5), the isostructural manganese aluminum phosphate (MnAPO-5) and magnesium aluminum phosphate (MAPO-36) were deposited onto titanium nitride-coated silicon wafers by laser ablation. The molecular sieve films function as the dielectric phase and were patterned with Au/Pd to complete the capacitor. The molecular sieve-based sensors exhibited capacitance changes upon exposure to CO2, CO, N-2 and H2O at room temperature. Significant responses to CO2 and CO were registered at levels as low as 50 and 100 ppm, respectively. (C) 1997 Elsevier Science S.A.