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Silver Filament Formation/Dissolution Dynamics Through a Polymer/Ionic liquid Composite by Direct-write

Chao, Zhongmou (2021) Silver Filament Formation/Dissolution Dynamics Through a Polymer/Ionic liquid Composite by Direct-write. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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A direct-write, electrochemical approach to the formation and dissolution of silver nanofilaments is demonstrated through a novel polymer electrolyte consisting of a UV-crosslinkable polymer, polyethylene glycol diacrylate (PEGDA) and an ionic liquid (IL), 1-butyl-3-methylimadozolium hexafluorophosphate ([BMIM]PF6). Nanofilaments are formed and dissolved at pre-programmed locations with a conductive atomic force microscope (c-AFM) using a custom script. Although the formation time generally decreases with increasing bias from 0.7 to 3.0 V, an unexpected non-monotonic maximum is observed ~2.0 V. At voltages approaching this region of inverted kinetics, IL electric double layers (EDLs) become detectable; thus, the increased nanofilament formation time can be attributed to electric field screening, which hinders silver electromigration and deposition. Scanning electron microscopy confirms that nanofilaments formed in this inverted region have significantly more lateral and diffuse features. Time dependent formation currents reveal two types of nanofilament growth dynamics: abrupt, where the resistance decreases sharply over as little as a few ms, and gradual where it decreases more slowly over hundreds of ms. Whether the resistance change is abrupt or gradual depends on the extent to which the EDL screens the electric field. Silver nanofilaments with gradual growth dynamics have potential application in neuromorphic computing. In this study, a linear (R2 > 0.9) dependence of conductance on the number of bias pulses is demonstrated—a signature feature that is required for neuromorphic application. Hundreds of distinguishable conductance states ranging from 235 to 260 microsimens can be accessed using a low read bias. These results show that novel PEGDA/IL composite electrolyte enables the gradual formation and dissolution of silver nanofilament with tunable conductance states, making it a promising candidate to advance neuromorphic applications.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Chao, Zhongmouzhc47@pitt.eduzhc470000-0002-9882-4440
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairFullerton-Shirey,
Committee MemberMcKone,
Committee MemberLaaser,
Committee MemberBeckman,
Date: 26 January 2021
Date Type: Publication
Defense Date: 28 October 2020
Approval Date: 26 January 2021
Submission Date: 30 October 2020
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 189
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical and Petroleum Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: silver filament, polymer electrolyte, ionic liquid, neuromorphic computing
Date Deposited: 26 Jan 2021 18:12
Last Modified: 26 Jan 2021 18:12


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