A Capacitance Type Chemical Sensor Based on AlPO4-5 Molecular Sieves

Thin films of AlPO 4 -5 molecular sieves have been employed as the dielectric phase in a capacitance type chemical sensor. AlPO 4 -5 was deposited onto titanium nitride (bottom electrode) coated silicon wafers by laser ablation. A subsequent hydrothermal treatment of the ablated AlPO 4 -5 films was found to enhance the crystallinity. The capacitance sensor configuration was completed by the deposition of Pd/Au pads (upper electrode) through a mask. AlPO 4 -5 based sensors exhibited significant changes in capacitance upon exposure to small molecules such as CO 2, CO, N 2, and H 2 O.