Catalytic metal-gate field effect transistors based on SiC for indoor air quality control

D Puglisi,M Andersson,A Lloyd Spetz,J Eriksson,C Bur,A Schuetze

doi:10.5194/jsss-4-1-2015

Abstract

Abstract. High-temperature iridium-gated field effect transistors based on silicon carbide have been used for sensitive detection of specific volatile organic compounds (VOCs) in concentrations of health concern, for indoor air quality monitoring and control. Formaldehyde, naphthalene, and benzene were studied as hazardous VOCs at parts per billion (ppb) down to sub-ppb levels. The sensor performance and characteristics were investigated at a constant temperature of 330 °C and at different levels of relative humidity up to 60%, showing good stability and repeatability of the sensor response, and excellent detection limits in the sub-ppb range.

Highlights

Common living environments such as homes, schools, or workplaces, where the exposure to indoor air pollutants is continuous or prolonged, have become dangerous sites of health problems related to bad air quality
All organic chemical compounds with the potential to evaporate under normal indoor atmospheric conditions are defined as volatile organic compounds (VOCs)
We have already studied the temperature dependence on such Ir-gate SiC-FETs demonstrating that the best operating temperature is around 330 ◦C (Puglisi et al, 2014), and we have quantitatively investigated Pt-gate SiC-FETs under dynamic operation, demonstrating that temperature cycling is a powerful approach to increasing the selectivity of the gas sensors allowing discrimination of the three studied VOCs (Bur et al, 2014)

Summary

Introduction

Common living environments such as homes, schools, or workplaces, where the exposure to indoor air pollutants is continuous or prolonged, have become dangerous sites of health problems related to bad air quality. Field effect transistor devices based on silicon carbide (SiC-FETs) have been extensively studied in the last 15 years as high-performance, low-cost gas sensors for room- and high-temperature applications, such as emission monitoring, combustion control and exhaust after-treatment (Lloyd Spetz et al, 2013a, b; Andersson et al, 2004, 2013), and, more recently, indoor air quality applications (Puglisi et al, 2014; Bur et al, 2012). Due to the chemical inertness and wide bandgap of SiC (3.26 eV for the 4H-SiC polytype), gas sensors based on this semiconductor material have the potential to work efficiently in harsh environmental conditions, like corrosive atmospheres and high temperatures, with notable advantages in terms of stability during long-term operation and the possibility of direct online control Such properties are suitable for indoor air quality applications, where the environment is at room temperature, but the sensors must be operated at high temperature to allow sensitive and selective detection of certain gas species.

Device fabrication

Electrical characterization

Gas tests

Results

Discussion and conclusions