Zhafira Darmastuti

The influence of gate bias and structure on the CO sensing performance of SiC based field effect sensors

SiC based Field Effect Transistor gas sensors with Pt as gate material have previously been shown to exhibit a binary CO response, sharply switching between a small and a large value with increasing CO or decreasing O2 concentration or temperature. In this study Pt gates with different structures have been fabricated by dc magnetron sputtering at different argon pressures and subjected to various CO/O2 mixtures under various temperatures and gate bias conditions. The influence of gate bias and gate structure on the CO response switch point has been investigated. The results suggest that the more porous the gate material or smaller the bias, the lower the temperature or higher the CO concentration required in order to induce the transition between a small and a large response towards CO. These trends are suggested to reflect the adsorption, spill-over, and reaction characteristics of oxygen chemisorbed to the Pt and insulator surfaces.

Improved chemical sensors track and control emissions

Sensitive, low-cost silicon carbide-based gas sensors can detect toxic emissions and hazardous nanoparticulate matter in previously untenable environments.

Chemical sensor systems for environmental and emission control

Focusing on environment and health aspects, the importance of monitoring and controlling dangerous gases and particulate matter increases. For this purpose we present a new version of silicon carbide based gas sensors with improved properties and suitable for high temperature and harsh environments such as power plants or car exhausts. Development of sulfur dioxide sensors for a power plant application is described as well as sensors for detection of ammonia in connection with the SCR process where urea is converted to ammonia, which reduces nitric oxide components in the exhausts. We also describe progress on nanoparticle detection, especially related to detection of the content of adsorbed particles through heating and detection of emitted molecules by a sensor array. Some results are also presented from impedance spectroscopy for detection of the concentration of nanoparticles but with the potential to reveal more details about the particles such as shape and kind of particles.

SiC based Field Effect Transistor for H 2 S detection

Experimental characterization and quantum chemical calculations were performed to evaluate the performance of a SiC based Field Effect Transistors with Pt and Ir gates as H2S sensors. The sensors were tested against various concentrations of H2S gas at the operating temperature between 150 and 350 °C. It was observed that Ir was very sensitive and selective to H2S at 350 °C. This phenomenon was studied further by comparing the reaction energy when H2S is exposed to Pt and Ir with density functional theory (DFT) calculations.

P2.5.3 SiC-FET Sensors for Methanol Leakage Detection

Pt and Ir SiC based Field Effect Transistor sensors were tested to detect low concentration of methanol (<200 ppm) for both process control and leak detection applications. Pt sensors gave good and very fast response at 200°C, while Ir sensors gave larger but much slower response. The presence of oxygen improved the response of the sensor which was favorable for the leak detection application. The influence of hydrogen and propene to the sensor response was also studied. Beside the experimental work, the detection mechanism and different sensing behavior of Pt and Ir were studied by quantum chemical calculations.