Spatial and Bidirectional Work Function Modulation of Monolayer Graphene with Patterned Polymer “Fluorozwitterists”

James Nicolas Pagaduan, Nicholas Hight-Huf, Le Zhou, Nicholas Dix, Uvinduni I. Premadasa, Benjamin Doughty, Thomas P. Russell, Ashwin Ramasubramaniam, Michael Barnes, Reika Katsumata, Todd Emrick

Research output: Contribution to journalArticlepeer-review

Abstract

Understanding the electronic properties resulting from soft-hard material interfacial contact has elevated the utility of functional polymers in advanced materials and nanoscale structures, such as in work function engineering of two-dimensional (2D) materials to produce new types of high-performance devices. In this paper, we describe the electronic impact of functional polymers, containing both zwitterionic and fluorocarbon components in their side chains, on the work function of monolayer graphene through the preparation of negative-tone photoresists, which we term “fluorozwitterists.” The zwitterionic and fluorinated groups each represent dipole-containing moieties capable of producing distinct surface energies as thin films. Kelvin probe force microscopy revealed these polymers to have a p-doping effect on graphene, which contrasts the work function decrease typically associated with polymer-to-graphene contact. Copolymerization of fluorinated zwitterionic monomers with methyl methacrylate and a benzophenone-substituted methacrylate produced copolymers that were amenable to photolithographic fabrication of fluorozwitterist structures. Consequently, spatial alteration of zwitterion coverage across graphene yielded stripes that resemble a lateral p-i-n diode configuration, with local increase or decrease of work function. Overall, this polymeric fluorozwitterist design is suitable for enabling simple, solution-based surface patterning and is anticipated to be useful for spatial work function modulation of 2D materials integrated into electronic devices.

Original languageEnglish
Pages (from-to)1629-1639
Number of pages11
JournalACS Central Science
Volume10
Issue number8
DOIs
StatePublished - Aug 28 2024

Funding

We gratefully acknowledge support from the National Science Foundation (NSF-BSF-1808011) and NSF-CHE-2203578. R.K. expresses gratitude for startup funding from UMass Amherst and a 3M Non-Tenured Faculty Award. J.N.P. thanks Dr. H. Greg Lin for assistance with UPS and XPS measurements and Dr. Zhefei Yang for assistance with ellipsometry measurements. This work was performed in part at the Harvard University Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Coordinated Infrastructure Network (NNCI), which is supported by the National Science Foundation under NSF award 1541959. SFG work by U.I.P. and B.D. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division; this work was produced by UT-Battelle LLC under Contract No. AC05-00OR22725 with the U.S. Department of Energy. T.P.R. was supported by the Air Force Office of Scientific Research under contract FA9550-21-1-0388.

FundersFunder number
Harvard University Center for Nanoscale Systems
Basic Energy Sciences
University of Massachusetts Amherst
U.S. Department of Energy
Cognitive Neuroscience Society
Office of Science
Chemical Sciences, Geosciences, and Biosciences Division
National Science FoundationNSF-CHE-2203578, 1541959, NSF-BSF-1808011
National Science Foundation
UT-BattelleAC05-00OR22725
UT-Battelle
Air Force Office of Scientific ResearchFA9550-21-1-0388
Air Force Office of Scientific Research

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