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Electrolyte Gating of Tips-Pentacene and Graphehe Field Effect Transistors

GUO, ZIWEI (2017) Electrolyte Gating of Tips-Pentacene and Graphehe Field Effect Transistors. Master's Thesis, University of Pittsburgh. (Unpublished)

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Electrolyte gating is widely used to explore transport in new materials for field effect transistors (FETs). An electric double layer (EDL) is formed within a few nanometers of the semiconductor surface leading to a huge accumulation of carriers in the channel (e.g., 1013 – 1014 cm-2 for electrons and holes). The improved gate control means that a lower operating voltage is required to achieve a particular drain current. In this thesis, we use electrolyte gating to explore the electrical performance of both an organic semiconductor, TIPS-pentacene, and a two dimensional (2D) semi-metal, graphene. To study whether or not the valency of the ions affects the sheet carrier density, Hall measurements were made on epitaxial graphene gated with a new solid polymer electrolyte, polyethylene oxide (PEO)/Mg(ClO4)2 in which Mg2+ can induce two electrons while the commonly used Li+ salt can only induce one. A side gate is used to drift ions into place and the temperature is lowered below the glass transition temperature of the polymer electrolyte to lock the ions into place. The highest sheet carrier densities are 7.9 ± 5.1 ×1013 cm-2 for holes and 3.4 ± 1.3×1013 cm-2 for electrons, which is an order of magnitude higher than that without electrolyte gating, and the values are comparable with those from Hall measurements on the same epitaxial graphene gated with PEO/LiClO4 by our group. These results indicate that the valency of ions will not have large impact on sheet carrier density. Additionally, a maximum hall mobility of 9.8 ± 4.5 × 104 cm2V-1s-1 was achieved. For TIPS-pentacene FETs, an ionic liquid. DEME-TFSI, was employed as the electrolyte gate. However, in this case, it was not possible to achieve strong gate control, and possible reasons for this observation are studied. One reason is that the large ionic mobility of DEME-TFSI leads to a large leakage current to the top gate. Also, the large device dimensions (i.e., channel wide of 960 μm and channel length of 50 μm), and a possible reaction between DEME-TFSI and TIPS-pentacene could contribute to the ineffective electrolyte gating. What is needed is a gate dielectric for which the leakage current to the top gate is at least 100 times smaller than IDS, chemical compatibility with TIPS-pentacene, and smaller gate and channel dimension.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairFullerton, Susanfullerton@pitt.edusfullert0000-0003-2720-0400
Committee MemberLi, Leilel55@pitt.edulel550000-0002-8679-9575
Committee MemberXiong, Fengf.xiong@pitt.eduFEX140000-0001-8383-5182
Date: 13 June 2017
Date Type: Publication
Defense Date: 31 March 2017
Approval Date: 13 June 2017
Submission Date: 4 April 2017
Access Restriction: 3 year -- Restrict access to University of Pittsburgh for a period of 3 years.
Number of Pages: 78
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: electrolyte gating, field effect transistor, solid polymer electrolyte, ionic liquid, graphene, TIPS-pentacene, electric double layer,
Date Deposited: 13 Jun 2017 14:43
Last Modified: 13 Jun 2020 05:15

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  • Electrolyte Gating of Tips-Pentacene and Graphehe Field Effect Transistors. (deposited 13 Jun 2017 14:43) [Currently Displayed]


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