GasFET for the detection of reducing gases
ABSTRACT A new gas sensor technology based on the signal read out of the work function change on sensitive films of thin or thick film SnO2 or Ga2O3 is used for the detection of reducing gases. The thick films are catalytic activated with Pd. The sensor device consists of a field effect transistor (FET) with suspended gate electrode prepared in hybrid flip chip technology (HFC-FET).Measurements with a Kelvin probe for testing the sensitive properties of the films and with complete assembled GasFET were performed. The SnO2 thick films activated with Pd show a high sensitivity to CO, hence concentrations lower than 1 vpm can be detected. The sensor response decreases with increasing temperature. A high cross sensitivity to oxygen and humidity is found only for very low oxygen concentrations (∼0 vol.%) or low humidity (∼0% r.h.). Thick films of SnO2 show a similar behavior to changes in the gas atmosphere in measurements performed using the Kelvin probe and with completely assembled GasFET sensors.
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ABSTRACT: Two types of SiC based field effect transistor sensors, with Pt or Ir gate, were tested to detect methanol in in the concentration range of 0-1600 ppm for both process control and leak detection applications. The methanol methanol response was investigated both with and without oxygen, since the process control might be considered considered as oxygen free application, while the sensor is operated in air during leak detection. Pt sensors offered offered very fast response with appreciably high response magnitude at 200 degrees C, while Ir sensors showed both both higher response and response time up to 300 degrees C, but this decreased considerably at 350 degrees C. Crosssensitivity sensivity effect in presence of oxygen, hydrogen, propene and water vapor was also investigated. The presence presence of oxygen improved the response of both sensors, which is favorable for the leak detection application. application. Hydrogen had a large influence on the methanol response of both sensors, propene had a negligible negligible influence, while water vapor changed direction of the methanol response for the Pt sensor. The detection mechanism and different sensing behavior of Pt and Ir gate sensors were discussed in the light light of model reaction mechanisms derived from hybrid density-functional theory quantum-chemical calculations.Sensors and Actuators B Chemical 10/2013; 187:553-562. DOI:10.1016/j.snb.2013.04.019 · 3.84 Impact Factor
Conference Paper: Optimized integrated micro-hotplates in CMOS technology[Show abstract] [Hide abstract]
ABSTRACT: Within this work the development of integrated Micro-HotPlates (μHPs) for gas sensing applications as a System-On Chip (SOC) is presented. As gas sensors exploit resistance variations of sensing materials like SnO2 at high operating temperatures, integrated μHPs are required for the dynamic and low power operation of these sensors. The optimized μHP structures consist of fully released membranes with polysilicon heaters in the oxide stack and suspension arms to the bulk silicon. Thanks to the optimized μHP design very low power consumption of Pel ~20mW at high temperatures up to T=400°C together with a thermal uniformity of only ΔT~1K across the active area ending up in the highest reported efficiency of =26-20K/mW for standard CMOS hotplates is achieved. Further a rise/fall time trise/tfall =4.5/5.4ms was measured. Long term stability of the μHP has been proven applying ten million measurement cycles. Thermography confirmed the temperature distribution and functionality. The realized hotplates cover a heating area of AμHP=100×100μm2/70×70μm2 at arm lengths of larm=70μm/50μm respectively. The chips have been realized in 0.35μm standard CMOS technology and released in a post process MEMS-etching step.New Circuits and Systems Conference (NEWCAS), 2013 IEEE 11th International; 01/2013