Open-air fabrication of oxide based cantilever gas sensors
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spatial atomic layer deposition, cantilever, gas sensor
The global market share of sensors and sensing technologies is expected to increase from $138 billion in 2017 to $283 billion (USD) by 2023 [1]. There is a push for an autonomous “sensor-driven world” where large amounts of data are continuously collected to make decisions for us. Gas sensor technology has applications in toxic gas detection, air quality monitoring, and early disease detection, to name a few. The development of sensors for the detection of nitrogen dioxide have become quite popular as it is a known air pollutant emitted from vehicle exhaust and causes significant respiratory problems [2]. The sensing of acetone in exhaled breath is also popular, as it can be used as a diagnostic indicator for Type 1 diabetes and monitoring of blood glucose levels [3]. In gene ral, gas sensor research aims to have enhanced detection limits, quicker sensing times and improved reliability.
The desire to improve the sensitivity of chemical sensors down to the level of a few, or even a single, molecule has led to the development of a variety of ultrasensitive technologies, including dynamic cantilever gas sensors. Dynamic cantilever gas sensors work by oscillating the cantilever to its natural resonance frequency by typical MEMS (micro electromechanical system) based actuation methods. The adsorption of a target analyte on the cantilever increases its mass and shifts the resonance frequency. Typically, micro-scale resonant sensors are able to make indirect mass change estimations in the atto to zepto gram range [4]. Conventional cant ilever type sensors are comprised of a silicon structural layer with a thickness on the order of 1-10 microns. The silicon cantilever is then coated with a thin layer of a receptor material to enable adsorption of specific analytes.
The project involves the open–air fabrication of innovative cantilever gas sensors by Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD). AP-SALD is capable of producing high quality metal oxide thin films with precision control, as with conventional atomic layer deposition (ALD) or other vacuum-based techniques [5]. Thanks to the spatial separation of precursors, AP-SALD has the main benefits of being up to 2 orders of magnitude faster than ALD and of occurring in open atmospheric conditions, therefore it is not constrained to the size of a vacuum chamber and allows for scalability. Different oxide materials will be deposited, characterized and tested.
The desire to improve the sensitivity of chemical sensors down to the level of a few, or even a single, molecule has led to the development of a variety of ultrasensitive technologies, including dynamic cantilever gas sensors. Dynamic cantilever gas sensors work by oscillating the cantilever to its natural resonance frequency by typical MEMS (micro electromechanical system) based actuation methods. The adsorption of a target analyte on the cantilever increases its mass and shifts the resonance frequency. Typically, micro-scale resonant sensors are able to make indirect mass change estimations in the atto to zepto gram range [4]. Conventional cant ilever type sensors are comprised of a silicon structural layer with a thickness on the order of 1-10 microns. The silicon cantilever is then coated with a thin layer of a receptor material to enable adsorption of specific analytes.
The project involves the open–air fabrication of innovative cantilever gas sensors by Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD). AP-SALD is capable of producing high quality metal oxide thin films with precision control, as with conventional atomic layer deposition (ALD) or other vacuum-based techniques [5]. Thanks to the spatial separation of precursors, AP-SALD has the main benefits of being up to 2 orders of magnitude faster than ALD and of occurring in open atmospheric conditions, therefore it is not constrained to the size of a vacuum chamber and allows for scalability. Different oxide materials will be deposited, characterized and tested.
Informations
Thesis director: David MUNOZ-ROJAS
Thesis co-director: Kevin MUSSELMAN (University of Waterloo)
Thesis supervisor: Skandar BASROUR
Thesis started on: Jan. 2019
Doctoral school: I-MEP2
Thesis co-director: Kevin MUSSELMAN (University of Waterloo)
Thesis supervisor: Skandar BASROUR
Thesis started on: Jan. 2019
Doctoral school: I-MEP2
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