Elin Becker

Study of the Sensing Mechanism Towards Carbon Monoxide of Platinum-Based Field Effect Sensors

We have investigated the temperature dependence and the effect of hydrogen on the CO response of MISiC field effect device sensors. The evolution of adsorbates on a model sensor was studied by in situ DRIFT spectroscopy and correlated to sensor response measurements at similar conditions. A strong correlation between the CO coverage of the sensor surface and the sensor response was found. The temperature dependence and hydrogen sensitivity are partly in agreement with these observations, however at low temperatures it is difficult to explain the observed increase in sensor response with increasing temperature. This may be explained by the reduction of a surface oxide or removal of oxygen from the Pt/SiO2 interface at increasing temperatures. The sensing mechanism of MISiC field effect sensors is likely complex, involving several of the factors discussed in this paper.

In situ DRIFT study of hydrogen and CO adsorption on Pt/SiO 2 model sensors

The sensing mechanism towards carbon monoxide of metal insulator silicon carbide (MISiC) field effect devices used as sensors, has been studied by in situ FTIR spectroscopy in diffuse reflectance mode (DRIFT). The infrared studies were performed using a model sensor, where adsorption of CO in presence of oxygen and hydrogen has been studied. The results show that the CO adsorption on Pt varies with varying oxygen concentration, CO concentration, hydrogen exposure and temperature. When correlating the DRIFT spectroscopy with sensor signal measurements, the CO response of MISiC field effect devices appears to be connected to the CO coverage of the sensor surface.

In situ DRIFT study of the CO response mechanism of MISFET sensors using a Pt/SiO 2 model sensor

The temperature dependence of the sensor response towards CO of SiC-FET sensors has been studied by combining in situ DRIFT spectroscopy and sensor response measurements. The DRIFT spectroscopy studies have been performed on a model sensor representing the top layer of a SiC-FET sensor with porous Pt gate. Adsorbates on the model sensor have been studied at varying temperatures and gas concentrations, and correlated to sensor response measurements at similar experimental conditions. The results show that the temperature dependence partly can be correlated to the CO coverage of the surface. The switching point of the sensor response, observed at different temperatures depending on the CO and oxygen concentrations is well in accordance with the kinetics of the CO oxidation reaction.

Effect of water vapour on gallium doped zinc oxide nanoparticle sensor gas response

Zinc oxide is a wide band gap (~3.4 ev) semiconductor material, making it a promising material for high temperature applications, such as exhaust and flue environments where NO and NO2 monitoring is increasingly required due to stricter emission controls. In these environments water vapour and background levels of oxygen are present and, as such, the effect of humidity on the sensing characteristics of these materials requires further study. The reaction mechanisms in the presence of water vapour are poorly understood and there is a need for deeper understanding of the principles and mechanisms of gas response of these materials. An investigation of the influence of changing water vapour (H2O) and oxygen (O2) backgrounds on the response of nanoparticulate Ga-doped ZnO resistive sensors is presented.