Influence of removing PMMA residues on surface of CVD graphene using a contact-mode atomic force microscope

Ho, Chang-Hoi; Shehzad, Muhammad Arslan; Park, Sanghoon; Seo, Yongho

doi:10.1039/c6ra27436f

Cited by 77 publications

(72 citation statements)

References 39 publications

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“…Therefore, there have been many efforts to remove these PMMA residues by various techniques, among which thermal annealing in vacuum or inert gases are most widely applied. Nonetheless it has been reported that some PMMA residues still remain on the surface after thermal annealing, resulting in scattering and defects .…”

Section: Summary Of Test Results Of Electrical Characterization On Gfmentioning

confidence: 99%

Cleaning Transferred Graphene for Optimization of Device Performance

Xiao

Wan

Durkan

2019

Adv Materials Inter

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Section: Summary Of Test Results Of Electrical Characterization On Gfmentioning

confidence: 99%

Cleaning Transferred Graphene for Optimization of Device Performance

Xiao

Wan

Durkan

2019

Adv Materials Inter

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“…In contrast to the chemical and thermal approaches described above, a mechanical approach is to use an AFM tip to “sweep” the polymer residue off the surface in contact mode. This AFM cleaning method induces no chemical reactions, has no restriction on the type of 2D crystal, and can retain the original 2D crystal thickness and surface roughness . It has been applied to both exfoliated and CVD‐grown graphene on various substrates, and the carrier mobility of graphene after the cleaning was reported to increase by 20% compared to before cleaning .…”

Section: Introductionmentioning

confidence: 99%

“…While several studies have used the AFM contact‐mode‐cleaning technique on graphene and reported transfer characteristics and Hall resistance measurements, to our knowledge there are no similar reports on TMDs. More specifically, there is no report on the impact of polymer reside on the electrical performance of EDL‐gated TMDs.…”

Section: Introductionmentioning

confidence: 99%

“…More specifically, there is no report on the impact of polymer reside on the electrical performance of EDL‐gated TMDs. Given the particular challenge of cleaning TMDs by oxidative annealing or plasma, AFM cleaning provides a useful alternative; however, the experimental conditions (e.g., contact force) must be optimized; otherwise, polymer residue may not be completely removed . While this approach is not scalable in its current form, one advantage of AFM cleaning from a scientific standpoint is the ability to isolate contributions from polymer residue in well‐defined locations on the device (e.g., channel vs contacts).…”

Section: Introductionmentioning

confidence: 99%

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Impact of Post‐Lithography Polymer Residue on the Electrical Characteristics of MoS₂ and WSe₂ Field Effect Transistors

Liang

Toncini

et al. 2018

Adv Materials Inter

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The residue of common photo‐ and electron‐beam resists, such as poly(methyl methacrylate) (PMMA), is often present on the surface of 2D crystals after device fabrication. The residue degrades device properties by decreasing carrier mobility and creating unwanted doping. Here, MoS2 and WSe2 field effect transistors (FETs) with residue are cleaned by contact mode atomic force microscopy (AFM) and the impact of the residue on: 1) the intrinsic electrical properties, and 2) the effectiveness of electric double layer (EDL) gating are measured. After cleaning, AFM measurements confirm that the surface roughness decreases to its intrinsic state (i.e., ≈0.23 nm for exfoliated MoS2 and WSe2) and Raman spectroscopy shows that the characteristic peak intensities (E2g and A1g) increase. PMMA residue causes p‐type doping corresponding to a charge density of ≈7 × 1011 cm−2 on back‐gated MoS2 and WSe2 FETs. For FETs gated with polyethylene oxide (PEO)76:CsClO4, removing the residue increases the charge density by 4.5 × 1012 cm−2, and the maximum drain current by 247% (statistically significant, p < 0.05). Removing the residue likely allows the ions to be positioned closer to the channel surface, which is essential for achieving the best possible electrostatic gate control in ion‐gated devices.

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“…The overall prediction, in the case of suspended graphene, is that the doping effects should be small and strongly dependent on molecule orientation. [49][50][51] Adv. [22] They predicted a very different doping behavior, as compared to suspended graphene: for defective SiO 2 substrates, adsorbed water molecules shift and couple the substrate's impurity bands with graphene bands, leading to much stronger (hole-type) doping, as compared to suspended graphene.…”

Section: Wwwadvelectronicmatdementioning

confidence: 99%

Graphene Electromechanical Water Sensor: The Wetristor

Meireles

Neto

Ferrari

et al. 2019

Adv Elect Materials

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between water and graphene is crucial for building up novel and smart biointerfaces. [18,19] Additionally, the study of reactivity and structure of water at the graphene interface has also generated intriguing questions and controversial results. [20,21] For instance, several experimental works demonstrate that the charge transfer process that happens between graphene and water molecules is highly dependent on the underlying substrate. [20,22] Thus, it would be highly desirable to elucidate the above discussion by probing the electrical response of a suspended graphene membrane in contact with water without the presence of any substrate. We also believe that a precise understanding of the electrochemical behavior of water/graphene interface would be fundamental for developing novel and superior electrical, mechanical, and optical devices.In the present work, we develop a microfluidic platform that integrates suspended graphene membrane windows (with electrical contacts) with buried fluid channels to probe the electrical response of a graphene membrane in contact with water. The platform design provides a direct probing of the electrical response of the air/graphene/liquid interface without the presence of any underlying substrate. [23] Our results show a significant change of graphene resistivity (of about 25%) due to the presence of water in the microchannel. The identification of the physical mechanisms behind such strong change in resistivity is not A water-induced electromechanical response in suspended graphene atop a microfluidic channel is reported. The graphene membrane resistivity rapidly decreases to ≈25% upon water injection into the channel, defining a sensitive "channel wetting" device-a wetristor. The physical mechanism of the wetristor operation is investigated using two graphene membrane geometries, either uncovered or covered by an inert and rigid lid (hexagonal boron nitride multilayer or poly(methyl methacrylate) film). The wetristor effect, namely the water-induced resistivity collapse, occurs in uncovered devices only. Atomic force microscopy and Raman spectroscopy indicate substantial morphology changes of graphene membranes in such devices, while covered membranes suffer no changes, upon channel water filling. The results suggest an electromechanical nature for the wetristor effect, where the resistivity reduction is caused by unwrinkling of the graphene membrane through channel filling, with an eventual direct doping caused by water being of much smaller magnitude, if any. The wetristor device should find useful sensing applications in general micro-and nanofluidics.

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Influence of removing PMMA residues on surface of CVD graphene using a contact-mode atomic force microscope

Abstract: AFM cleaning technique can be a potential tool to clean the surface defects of 2D materials like TMDs, as well as graphene.

Cited by 77 publications

References 39 publications

Cleaning Transferred Graphene for Optimization of Device Performance

Cleaning Transferred Graphene for Optimization of Device Performance

Impact of Post‐Lithography Polymer Residue on the Electrical Characteristics of MoS₂ and WSe₂ Field Effect Transistors

Graphene Electromechanical Water Sensor: The Wetristor

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Influence of removing PMMA residues on surface of CVD graphene using a contact-mode atomic force microscope

Abstract: AFM cleaning technique can be a potential tool to clean the surface defects of 2D materials like TMDs, as well as graphene.

Cited by 77 publications

References 39 publications

Cleaning Transferred Graphene for Optimization of Device Performance

Cleaning Transferred Graphene for Optimization of Device Performance

Impact of Post‐Lithography Polymer Residue on the Electrical Characteristics of MoS2 and WSe2 Field Effect Transistors

Graphene Electromechanical Water Sensor: The Wetristor

Contact Info

Product

Resources

About

Impact of Post‐Lithography Polymer Residue on the Electrical Characteristics of MoS₂ and WSe₂ Field Effect Transistors