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Pagaduan J, Hight-Huf N, Zhou L, Dix N, Premadasa UI, Doughty B, Russell TP, Ramasubramaniam A, Barnes M, Katsumata R, Emrick T. Spatial and Bidirectional Work Function Modulation of Monolayer Graphene with Patterned Polymer "Fluorozwitterists". ACS CENTRAL SCIENCE 2024; 10:1629-1639. [PMID: 39220689 PMCID: PMC11363338 DOI: 10.1021/acscentsci.4c00704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/30/2024] [Accepted: 07/22/2024] [Indexed: 09/04/2024]
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.
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Affiliation(s)
- James
Nicolas Pagaduan
- Polymer
Science and Engineering Department, University
of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Nicholas Hight-Huf
- Department
of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Le Zhou
- Polymer
Science and Engineering Department, University
of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Nicholas Dix
- Department
of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Uvinduni I. Premadasa
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin Doughty
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Thomas P. Russell
- Polymer
Science and Engineering Department, University
of Massachusetts, Amherst, Massachusetts 01003, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Ashwin Ramasubramaniam
- Department
of Mechanical and Industrial Engineering and Materials Science Graduate
Program, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Michael Barnes
- Department
of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Reika Katsumata
- Polymer
Science and Engineering Department, University
of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Todd Emrick
- Polymer
Science and Engineering Department, University
of Massachusetts, Amherst, Massachusetts 01003, United States
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Selhorst R, Yu Z, Moore D, Jiang J, Susner MA, Glavin NR, Pachter R, Terrones M, Maruyama B, Rao R. Precision Modification of Monolayer Transition Metal Dichalcogenides via Environmental E-Beam Patterning. ACS NANO 2023; 17:2958-2967. [PMID: 36689725 DOI: 10.1021/acsnano.2c11503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Layered Transition Metal Dichalcogenides (TMDs) are an important class of materials that exhibit a wide variety of optoelectronic properties. The ability to spatially tailor their expansive property-space (e.g., conduction behavior, optical emission, surface interactions) is of special interest for applications including, but not limited to, sensing, bioelectronics, and spintronics/valleytronics. Current methods of property modulation focus on the modification of the basal surfaces and edge sites of the TMDs by the introduction of defects, functionalization with organic or inorganic moieties, alloying, heterostructure formation, and phase engineering. A majority of these methods lack the resolution for the development of next-generation nanoscale devices or are limited in the types of functionalities useful for efficient TMD property modification. In this study, we utilize electron-beam patterning on monolayer TMDs (MoSe2, WSe2 and MoS2) in the presence of a pressure-controlled atmosphere of water vapor within an environmental scanning electron microscope (ESEM). A series of parametric studies show local optical and electronic property modification depending on acceleration voltage, beam current, pressure, and electron dose. The ultimate pattern resolution achieved is 67 ± 9 nm. Raman and photoluminescence spectroscopies coupled with Kelvin Probe Force Microscopy reveal electron dose-dependent p-doping in the patterned regions, which we attribute to functionalization from the products of water vapor radiolysis (oxygen and hydroxyl groups). The modulation of the work function through patterning matches well with Density Functional Theory modeling. Finally, post-functionalization of the patterned areas with an organic fluorophore demonstrates a robust method to achieve nanoscale functionalization with high fidelity.
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Affiliation(s)
- Ryan Selhorst
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
- UES Inc., 4401 Dayton-Xenia Rd., Dayton, Ohio 45433, United States
| | - Zhuohang Yu
- Department of Materials Science and Engineering, The Pennsylvania State University, 221 Steidle Building, University Park, Pennsylvania 16802, United States
| | - David Moore
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Jie Jiang
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Michael A Susner
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Nicholas R Glavin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Ruth Pachter
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Mauricio Terrones
- Department of Materials Science and Engineering, The Pennsylvania State University, 221 Steidle Building, University Park, Pennsylvania 16802, United States
| | - Benji Maruyama
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Rahul Rao
- Materials and Manufacturing Directorate, Air Force Research Laboratory, 2179 12th Street, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
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Hight-Huf N, Pagaduan JN, Katsumata R, Emrick T, Barnes MD. Stabilization of Three-Particle Excitations in Monolayer MoS 2 by Fluorinated Methacrylate Polymers. J Phys Chem Lett 2022; 13:4794-4799. [PMID: 35613709 DOI: 10.1021/acs.jpclett.2c01150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
While extrinsic factors, such as substrates and chemical doping, are known to strongly influence visible photoemission from monolayer MoS2, key fundamental knowledge for p-type polymeric dopants is lacking. We investigated perturbations to the electronic environment of 2D MoS2 using fluorinated polymer coatings and specifically studied stabilization of three-particle states by monitoring changes in intensities and emission maxima of three-particle and two-particle emissions. We calculated changes in carrier density and trion binding energy, the latter having an additional contribution from MoS2 polarization by the polymer. Polarization is further suggested by Kelvin probe force microscopy (KPFM) measurements of large Fermi level shifts. Changes similar in magnitude, but opposite in sign, were observed in 2D MoS2 coated with an analogous nonfluorinated polymer. These findings highlight the important interplay between electron exchange and electrostatic interactions at the interface between polymers and transition metal dichalcogenides (TMDCs), which govern fundamental electronic properties relevant to next-generation devices.
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Hight-Huf N, Nagar Y, Levi A, Pagaduan JN, Datar A, Katsumata R, Emrick T, Ramasubramaniam A, Naveh D, Barnes MD. Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides. ACS APPLIED MATERIALS & INTERFACES 2021; 13:47945-47953. [PMID: 34607423 DOI: 10.1021/acsami.1c13505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We investigated the nature of graphene surface doping by zwitterionic polymers and the implications of weak in-plane and strong through-plane screening using a novel sample geometry that allows direct access to either the graphene or the polymer side of a graphene/polymer interface. Using both Kelvin probe and electrostatic force microscopies, we observed a significant upshift in the Fermi level in graphene of ∼260 meV that was dominated by a change in polarizability rather than pure charge transfer with the organic overlayer. This physical picture is supported by density functional theory (DFT) calculations, which describe a redistribution of charge in graphene in response to the dipoles of the adsorbed zwitterionic moieties, analogous to a local DC Stark effect. Strong metallic-like screening of the adsorbed dipoles was observed by employing an inverted geometry, an effect identified by DFT to arise from a strongly asymmetric redistribution of charge confined to the side of graphene proximal to the zwitterion dipoles. Transport measurements confirm n-type doping with no significant impact on carrier mobility, thus demonstrating a route to desirable electronic properties in devices that combine graphene with lithographically patterned polymers.
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Affiliation(s)
- Nicholas Hight-Huf
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Yehiel Nagar
- Faculty of Engineering and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Adi Levi
- Faculty of Engineering and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - James Nicolas Pagaduan
- Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Avdhoot Datar
- Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Reika Katsumata
- Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Todd Emrick
- Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Ashwin Ramasubramaniam
- Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Doron Naveh
- Faculty of Engineering and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Michael D Barnes
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, United States
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Pagaduan JN, Hight-Huf N, Datar A, Nagar Y, Barnes M, Naveh D, Ramasubramaniam A, Katsumata R, Emrick T. Electronic Tuning of Monolayer Graphene with Polymeric "Zwitterists". ACS NANO 2021; 15:2762-2770. [PMID: 33512145 DOI: 10.1021/acsnano.0c08624] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Work function engineering of two-dimensional (2D) materials by application of polymer coatings represents a research thrust that promises to enhance the performance of electronic devices. While polymer zwitterions have been demonstrated to significantly modify the work function of both metal electrodes and 2D materials due to their dipole-rich structure, the impact of zwitterion chemical structure on work function modulation is not well understood. To address this knowledge gap, we synthesized a series of sulfobetaine-based zwitterionic random copolymers with variable substituents and used them in lithographic patterning for the preparation of negative-tone resists (i.e., "zwitterists") on monolayer graphene. Ultraviolet photoelectron spectroscopy indicated a significant work function reduction, as high as 1.5 eV, induced by all polymer zwitterions when applied as ultrathin films (<10 nm) on monolayer graphene. Of the polymers studied, the piperidinyl-substituted version, produced the largest dipole normal to the graphene sheet, thereby inducing the maximum work function reduction. Density functional theory calculations probed the influence of zwitterion composition on dipole orientation, while lithographic patterning allowed for evaluation of surface potential contrast via Kelvin probe force microscopy. Overall, this polymer "zwitterist" design holds promise for fine-tuning 2D materials electronics with spatial control based on the chemistry of the polymer coating and the dimensions of the lithographic patterning.
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Affiliation(s)
| | | | | | - Yehiel Nagar
- Faculty of Engineering and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | | | - Doron Naveh
- Faculty of Engineering and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
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Zuo P, Jiang L, Li X, Ran P, Li B, Song A, Tian M, Ma T, Guo B, Qu L, Lu Y. Enhancing charge transfer with foreign molecules through femtosecond laser induced MoS 2 defect sites for photoluminescence control and SERS enhancement. NANOSCALE 2019; 11:485-494. [PMID: 30543248 DOI: 10.1039/c8nr08785g] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Defect/active site control is crucial for tuning the chemical, optical, and electronic properties of MoS2, which can adjust the performance of MoS2 in application areas such as electronics, optics, catalysis, and molecular sensing. This study presents an effective method of inducing defect/active sites, including micro/nanofractured structures and S atomic vacancies, on monolayer MoS2 flakes by using femtosecond laser pulses, through which physical-chemical adsorption and charge transfer between foreign molecules (O2 or R6G molecules) and MoS2 are enhanced. The enhanced charge transfer between foreign molecules (O2 or R6G) and femtosecond laser-treated MoS2 can enhance the electronic doping effect between them, hence resulting in a photoluminescence photon energy shift (reaching 0.05 eV) of MoS2 and Raman enhancement (reaching 6.4 times) on MoS2 flakes for R6G molecule detection. Finally, photoluminescence control and micropatterns on MoS2 and surface-enhanced-Raman-scattering (SERS) enhancement of MoS2 for organic molecule detection are achieved. The proposed method, which can control the photoluminescence properties and arbitrary micropatterns on MoS2 and enhance its chemicobiological sensing performance for organic/biological molecules, has advantages of simplicity, maskless processing, strong controllability, high precision, and high flexibility, highlighting the superior ability of femtosecond laser pulses to achieve the property control and functionalization of two-dimensional materials.
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Affiliation(s)
- Pei Zuo
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P.R. China.
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