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ppb level detection of NO2 using a WO3 thin film-based sensor: material optimization, device fabrication and
Chandra Shekhar Prajapati1, Navakanta Bhat1
1Centre for Nano Science and Engineering, Indian Institute of Science Bangalore-560012 Karnataka India chandrashekhar@iisc.ac.in.
RSC Advances
|May 11, 2022
Summary
This study developed a highly sensitive tungsten trioxide (WO3) gas sensor for detecting nitrogen dioxide (NO2). The optimized 85 nm film achieved a 16 ppb lower limit of detection at 150 °C.
Area of Science:
- Materials Science
- Nanotechnology
- Chemical Sensing
Background:
- Developing highly sensitive and selective gas sensors is crucial for environmental monitoring and safety.
- Tungsten trioxide (WO3) is a promising material for gas sensing applications due to its unique electrical and optical properties.
- Integrating gas sensors with microelectronics platforms enables portable and real-time monitoring solutions.
Purpose of the Study:
- To investigate the thickness-dependent nitrogen dioxide (NO2) sensing characteristics of reactive-ion magnetron sputtered WO3 films.
- To optimize WO3 film thickness for integration with CMOS platforms and portable applications.
- To develop a highly sensitive, selective, stable, and portable NO2 gas sensor.
Main Methods:
- Fabrication of WO3 films using reactive-ion magnetron sputtering.
- Morphological and electrical characterization of the sputtered films.
- Integration of the sensing material with a Micro-Electro-Mechanical Systems (MEMS) platform.
- Optimization of operating temperature and film thickness for enhanced sensing performance.
- Development of a temperature overshoot protocol for rapid sensor recovery.
Main Results:
- An optimized WO3 film thickness of approximately 85 nm was identified.
- The sensor achieved a lower limit of detection of 16 ppb and a detection precision of 39 ppb for NO2 at 150 °C.
- A high sensor response of 26% was observed for a low NO2 concentration (16 ppb).
- A temperature overshoot protocol effectively resolved the issue of longer recovery times.
- The sensor chip, with a size of 1 mm², demonstrated low power consumption (6.6 mW) for the micro-heater.
Conclusions:
- Optimization of WO3 film thickness and operating temperature is critical for developing high-performance gas sensors.
- The developed WO3-based MEMS sensor exhibits excellent sensitivity, selectivity, and stability for NO2 detection.
- The sensor's low power consumption and small form factor make it suitable for portable indoor and outdoor applications.
- The integration of sensing materials with microelectronic platforms paves the way for advanced gas sensing technologies.
