Liang, Jierui
(2021)
Ion-controlled electronics enabled by electric double layer gating of two-dimensional materials.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
An electric double layer transistor (EDLT) is a type of emerging, ion-controlled electronic device that uses ions in an electrolyte to induce charge in the transistor channel by field-effect. Because the EDL formed at the electrolyte/channel interface under an applied field acts as an interfacial capacitor (thickness < 1 nm), large capacitance densities, corresponding to sheet carrier densities exceeding 10^14 cm^-2, can be induced in two-dimensional (2D) crystals. This dissertation presents efforts to both improve EDL gating performance and add new functionality to 2D EDLTs using three newly developed ion conductors.
My first contribution was demonstrating the removal of polymeric resist residue from the channel using atomic force microscopy (AFM) in contact mode. This technique provides a molecularly clean 2D surface for depositing a nanometer-thin ion conductor and for achieving the strongest EDL gating possible. My second contribution was the development of a monolayer electrolyte field-effect transistor as non-volatile memory (MERAM) based on WSe2. The electrolyte is a single molecule thick and has two stable states which can be modulated by a gate bias. After programming, MERAM has an On-Off ratio exceeding 10^4 at a 0V read voltage, which is repeatable over 1000 program/erase cycles; the retention time for each state exceeds 6 hours (maximum cycles and time measured). The third contribution was the development of a single-ion conductor where anions are covalently bound to the backbone of the polymer, leaving only the cations free to form an EDL at the channel. Experiments and modeling support that the single-ion conductor gating can create an electrostatic imbalance that induces strain on a suspended MoTe2 channel to exploit the semiconductor-to-metal phase transition for low-power 2D transistors. The last contribution was demonstrating EDL “locking” using a doubly polymerizable ionic liquid (DPIL) developed by our collaborators. Ions are drifted into place and immobilized by thermally/photo-induced polymerization. This concept has been used on graphene to lock a lateral p-n junction. A thermally triggerable ion release was also demonstrated for ion-unlocking.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
13 June 2021 |
| Date Type: |
Publication |
| Defense Date: |
29 October 2020 |
| Approval Date: |
13 June 2021 |
| Submission Date: |
18 March 2021 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
220 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
iontronics, ionic gating, electric double layer, field effect transistor, 2D material, EDLT, non-volatile memory, polymer electrolyte |
| Date Deposited: |
13 Jun 2021 17:47 |
| Last Modified: |
13 Jun 2021 17:47 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/40392 |
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