Bithiazolidinylidene polymers: synthesis and electronic interactions with transition metal dichalcogenides

Selhorst, Ryan; Wang, Peijian; Barnes, Michael D.; Emrick, Todd

doi:10.1039/c8sc01416g

Cited by 8 publications

(12 citation statements)

References 26 publications

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“…As the organic overlayer, we selected poly(methacryloyloxyethyl phosphorylcholine) (PMPC) as a copolymer with methyl methacrylate and cross-linkable benzophenone methacrylamide comonomers (Figure c). Unlike previous hybrid 2D systems, which show clear evidence of charge-doping, − ,− we find that the dominant effect in this PMPC copolymer/graphene system is a change in polarization due to dipole interactions, i.e., a shift in the Fermi level in response to the PC dipoles (Figure d).…”

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confidence: 78%

“…The key to controlling electronic properties, such as Fermi energy, band alignment, and carrier density, lies in the interactions between the organic layer (typically functioning as a charge dopant) and the 2D material. Such hybrid materials can be divided into a chemical functionalization − (covalent surface modification) group and a non-covalent group. − Additional approaches to the electronic modification of 2D materials include substitutional doping − and ferroelectric gating. − We view non-covalent surface modification as an attractive doping strategy without disrupting the pristine 2D layer, while also providing an opportunity for lithographic patterning and improved processability. , Although ferroelectric gating is attractive for producing addressable circuit elements, our non-covalent hybrid material approach is driven by applications where the additional circuitry needed to produce the forming and coercive fields represents undesired complexity along with concerns for the stability of the electronic properties of interest. While we previously reported non-covalent charge doping in graphene using sulfobetaine zwitterions, , here, we find phosphorylcholine (PC)-substituted polymers, of the type typically employed in non-fouling coatings, to have a remarkable impact on graphene that, as we describe, is chemically and electronically distinct from typical dopant adsorbates.…”

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confidence: 99%

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Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides

Hight‐Huf

Nagar

Levi

et al. 2021

ACS Appl. Mater. Interfaces

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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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confidence: 78%

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confidence: 99%

Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides

Hight‐Huf

Nagar

Levi

et al. 2021

ACS Appl. Mater. Interfaces

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“…Through such methods, the fundamental electronic properties of 2D materials, such as work function ( i.e. , the energy required to promote an electron from the Fermi level to vacuum), can be modulated to adjust band alignment, tune charge injection barriers, and control the charge carrier type and density. , For graphene, current approaches to work function engineering of this type include chemical doping by atomic insertion into the 2D structure, gas adsorption, electrostatic gating, and application of mechanical strain. − An alternative approach to modulate graphene electronics is by its contact with synthetic polymers, which is advantageous for the outstanding film-forming properties and rich chemical variation available with polymers. − Moreover, such hard–soft ( i.e ., 2D material-polymer) interfaces enhance 2D materials properties, processing, and electronic function via the combination of polymeric chemical functionality with lithographic patterning methods.…”

Section: Introductionmentioning

confidence: 99%

Electronic Tuning of Monolayer Graphene with Polymeric “Zwitterists”

Pagaduan¹,

Hight‐Huf²,

Datar³

et al. 2021

ACS Nano

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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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“…(Figure 1d). [51,[80][81][82][83][84][85][86][87][88][89][90][91] Due to numerous unique properties of 2D TMCs, devices such as transistors, photodetectors and photodiodes based on 2D TMCs have been actively pursued. The ultimate destination of the miniaturization of the electronic devices will be one atomic thickness.…”

Section: Introductionmentioning

confidence: 99%

“…(Figure 1d). [51,[80][81][82][83][84][85][86][87][88][89][90][91] Due to numerous unique properties of 2D TMCs, devices such as transistors, photodetectors (PDs), and photodiodes based on 2D TMCs have been actively pursued. The ultimate destination of the miniaturization of the electronic devices will 2D transition metal chalcogenides (TMCs) have attracted tremendous interest from both the scientific and technological communities due to their variety of properties and superior tunability through layer number, composition, and interface engineering.…”

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Toward Wafer‐Scale Production of 2D Transition Metal Chalcogenides

Wang

Yang

2021

Adv Elect Materials

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When the timeline reached 2004, graphene, the single layer of graphite, was discovered through a scotch-tape exfoliation method and was found to have ultrahigh mobility. [25][26][27] Various 2D materials such as transition metal chalcogenides (TMCs), [28][29][30] boron nitrides (BNs), [31,32] black phosphorus, [33,34] and some new materials including Si, [35] Te, [36] and black arsenic-phosphorus [37] were subsequently synthesized, enabling the fabrication of numerous novel devices. The field of 2D materials is now making strong voice, which is no longer ignored by the scientific and technological community. [38][39][40] Among the various 2D materials, the TMCs constituted by the transition metal elements (M) and the chalcogen elements (X) are a large family. M can range from group 4B to group 10 in the periodic table, while X is S, Se, or Te. [41][42][43][44][45][46][47] Figure 1a exhibits the binary TMCs that have already been explored. This variation of composition of elements transfers to a wide range of properties ranging from insulators (e.g., HfS 2 ), [48,49] semiconductors (e.g., MoS 2 , WS 2 ), [50,51] semimetals (e.g., MoTe 2 , TiSe 2 ), [52,53] to metals (e.g., NbSe 2 , VS 2 ). [54][55][56] Furthermore, TMCs can form alloys in the formula such as WSe 2−x S x , with composition-tunable properties. [57][58][59] Unlike semimetallic graphene, semiconducting TMCs usually possess a bandgap. For example, MoS 2 exhibits a bandgap, transitioning from indirect bandgap to direct bandgap when it thins from bulk phase to monolayer (Figure 1b), boosting the photoluminescence (PL) efficiency. [51,[60][61][62] Additionally, inversion symmetry breaking and large spin-orbit interaction, resulting in two energetic degenerate but inequivalent valleys in the band structure of a TMC (Figure 1c), may lead to breakthroughs in valleytronics and spintronics. [63][64][65][66][67][68][69][70] A few TMCs (e.g., NbSe 2 , TaS 2 , VSe 2 ) have shown superconductivity, [71,72] charge density wave [73,74] and Mott transition (transition from metal to nonmetal). [75,76] In addition, some novel TMCs such as Fe 3 GeTe 2 display intrinsic magnetism with gate-tunable Curie points. [66,77] Semimetallic TMCs like WTe 2 show topological structures in the energy band, enabling the study on topological physics. [78,79] The rich intrinsic properties and superior tunability of TMCs hold great promise for all kinds of technologically important applications in electronics, optoelectronics, spintronics, valleytronics, etc. (Figure 1d). [51,[80][81][82][83][84][85][86][87][88][89][90][91] Due to numerous unique properties of 2D TMCs, devices such as transistors, photodetectors (PDs), and photodiodes based on 2D TMCs have been actively pursued. The ultimate destination of the miniaturization of the electronic devices will 2D transition metal chalcogenides (TMCs) have attracted tremendous interest from both the scientific and technological communities due to their variety of properties and superior tunability through layer number, composition, and inter...

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Bithiazolidinylidene polymers: synthesis and electronic interactions with transition metal dichalcogenides

Abstract: We describe the synthesis and characterization of polymers bearing sulfur-rich, electron-accepting bithiazolidinylidene (BT) groups, and probe their electronic impact on 2-D transition metal dichalcogenides (TMDCs).

Cited by 8 publications

References 26 publications

Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides

Polarization-Driven Asymmetric Electronic Response of Monolayer Graphene to Polymer Zwitterions Probed from Both Sides

Electronic Tuning of Monolayer Graphene with Polymeric “Zwitterists”

Toward Wafer‐Scale Production of 2D Transition Metal Chalcogenides

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