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Flexible Graphene Transistor Architecture for Optical Sensor Technology.

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Title:Flexible Graphene Transistor Architecture for Optical Sensor Technology.
Authors:Ordonez, Richard C.
Contributors:Electrical Engineering (department)
Date Issued:May 2017
Publisher:University of Hawaiʻi at Mānoa
Abstract:The unique electrical and optoelectronic properties of graphene allow tunable conductivity and broadband electromagnetic absorption that spans the ultraviolet and infrared regimes. However, in the current state-of-art graphene sensor architectures, junction resistance and doping concentration are predominant factors that affect signal strength and sensitivity. Unfortunately, graphene produces high contact resistances with standard electrode materials (~few kilo-ohms), therefore, signal is weak and large carrier concentrations are required to probe sensitivity. Moreover, the atomic thickness of graphene enables the potential for flexible electronics, but there has not been a successful graphene sensor architecture that demonstrates stable operation on flexible substrates and with minimal fabrication cost.
In this study, the author explores a novel 3-terminal transistor architecture that integrates two-dimensional graphene, liquid metal, and electrolytic gate dielectrics (LM-GFETs: Liquid Metal and Graphene Field-Effect Transistors). The goal is to deliver a sensitive, flexible, and lightweight transistor architecture that will improve sensor technology and maneuverability. The reported high
thermal conductivity of graphene provides potential for room-temperature thermal management without the need of thermal-electric and gas cooling systems that are standard in sensor platforms. Liquid metals provide a unique opportunity for conformal electrodes that maximize surface area contact, therefore, enable flexibility, lower contact resistance, and reduce damage to the graphene materials involved. Lastly, electrolytic gate dielectrics provide conformability and high capacitances needed for high on/off rations and electrostatic gating.
Results demonstrated that with minimal fabrication steps the proposed flexible graphene transistor architecture demonstrated ambipolar current-voltage transfer characteristics that are comparable to the current state-of-the-art. An additional investigation demonstrated PN junction operation and the successful integration of the proposed architecture into an optoelectronic application with the use of semiconductor 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.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017.
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Electrical Engineering

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