A Multifunctional Suspended Graphene Array Sensor Chipset

Abstract

Graphene was first isolated in Manchester in 2004 and immediately started a buzz of excitement, with some heralding a new era in electronics. In the years that followed, much of the initial hype did not turn into market products in the consumer electronics sector, and many efforts worldwide reported finding themselves “beached” after encountering significant barriers to adoption, particularly in the up scaling efforts. Three major obstacles reported had been: the effect of interaction with the substrate “muffling” the graphene properties, the quality of the transferred graphene sheet (which tends to be chemical vapor deposition (CVD) grown and polycrystalline), and a fabrication method compatible with standard industrial microelectronics fabrication. CVD grown graphene material used as a freestanding (or suspended) sheet dry transferred onto a patterned Si substrate, and a lift-off less microelectronics compatible fabrication recipe, is the solution that is explored in this thesis. We will show how CVD material of sufficient quality, when suspended over cavities etched in SiO2, can have much closer properties to the ideal graphene than if placed on bare SiO2. We will further show that a complete sensor chipset, comprising many graphene devices, can be effectively used as a volatile organic compounds (VOC) sensor, with cross-sensitivity to humidity and pressure being sufficiently low to not affect the devices. VOC sensor chips were tested for a variety of gasses such as NH3 NO2, CO and toluene, exhibiting distinct features compared to using supported graphene, with clear unique selling points in terms of the speed of response, and large potential for obtaining very low limits of detection compared to current commercial technology. We have tested the device against a commercial photo ionization detection (PID) and showed that as a toluene sensor, our chip already exhibits commercial competitiveness. Finally, we will show that the potential for unique specific graphene-based VOC sensors could open up new era in a variety of field including gas and oil industry, industrial process monitoring, air quality monitoring and medical diagnostics.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Leszek Majewski (Supervisor), Neil Dixon (Supervisor) & Max Migliorato (Supervisor)