University of Hawaii

Electrical Engineering

Flexible Graphene Transistor Architecture for Optical Sensor Technology

Date: 2017-04-07           Add to Google Calendar
Time: 10:30am-12:30pm
Location: Holmes Hall 389
Speaker: Richard Christopher Ordonez, PhD Candidate


The unique electrical optoelectronic properties of graphene allow tunable conductivity and broadband electromagnetic absorption that spans the ultraviolet and infrared regimes. In addition, the atomic thickness of graphene enables the potential for flexible electronics. However, there has not been a successful graphene sensor architecture that demonstrates stable operation on flexible substrates and with minimal fabrication cost. In this study, I explored a novel 3-terminal transistor architecture that integrates two-dimensional graphene, liquid metal, and electrolytic ate dielectrics (LM-GFETs: Liquid Metal and Graphene Field-Effect Transistors). Liquid-metals provided a unique opportunity for conformal electrodes that maximized surface area contact, therefore, enabled flexibility, lowered contact resistance, and reduced damage to the graphene materials involved. Furthermore, electrolytic gate dielectrics were used to provide high capacitance needed for high on-current and low-voltage operation. The goal of this study was to deliver a sensitive, flexible, and lightweight transistor architecture that will improve sensor technology and maneuverability. In addition, allow researchers to explore graphene phenomena without the need for expensive fabrification processes.

Results showed that with minimal fabrication steps the proposed LM-GFET devices demonstrated ambipolar current-voltage transfer characteristics that were comparable to current state-of-the-art graphene field-effect transistors. An additional investigation demonstrated PN junction operation and the successful integration of the proposed architecture inot an optoelectronic application with the use of seminconductor quantum dots in contact with the graphene material that acted as optical absorbers to increase detector gain. Applications that can benefit from such technology advancement include Nano-satellites (Nanosat), Underwater autonomous vehicles (UAV), and airborne platforms in which flexibility and sensitivity are critical parameters that must be optimized to increase mission duration and range.