FAST TEMPERATURE-PROGRAMMED SENSING FOR MICRO-HOTPLATE GAS SENSORS

We describe an operating mode of a gas sensor that greatly enhances th e capability of the device to determine the composition of a sensed ga s, The device consists of a micromachined hotplate with integrated hea ter, heat distribution plate, electrical contact pads, and sensing fil m, The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for adsorption, des orption, and reaction of gases on the sensing surface during sensor op eration, A repetitive train of temperature pulses produces a patterned conductance response that depends on the gas composition, as well as the temperature pulse width, amplitude, and specific sequence of pulse s, Results are shown for the vapors of water, ethanol, methanol, forma ldehyde, and acetone.