Graphene and CNT Microsensors for Gas and Vacuum Sensing Applications

Abstract

Since the discovery of fullerene and carbon nanotubes (CNT), carbon nanomaterials have attracted enormous interest in sensor applications and subsequently resulted into new classes of sensor devices[1]. This became more relevant because existing solid state materials used for gas testing/sensing encounter limitations related to long term stability and restricted measurement exactness. Graphene and CNTs have been studied for gas sensing applications due to their outstanding physical, electronic, mechanical and optical properties[2]. The high surface-to-volume ratio (giving a large exposed area) and mono-atomic thickness of graphene sheets makes it suitable for subppm gas sensing. The device architecture for graphene sensor includes both planar and cavity based devices. These graphene membranes are easily deflected under small pressure, resulting in change in the graphene electronic properties[3]. The work developed towards this thesis aimed for the fabrication and characterization of different micro-sensors using different architectures to selectively detect different gases. This is accomplished by demonstrating and validating the concept of triangulation for gas detection that is based on expanding the dimensions of the solution space to come up with a unique signature for a given gas. Moreover, using the resistance change as unique response surface for a given gas using two different micro sensors architectures, cavity and non-cavity, at different operating pressure allows us to selectively distinguish between the different gases. Different synthesis methods of carbon nanomaterials has been explored, however, CVD graphene is in the dominance position among the established carbon nanomaterials aimed towards achieving high gas selectivity. Moreover, the sensor were packaged for testing under vacuum as a function of the different gases O₂, CO₂, N₂ and Ar. Furthermore, the effect of multilayer CVD graphene on the gas sensor performance has been studied.

Date of Award	Jul 2018
Original language	American English