| 1. |
- Chen, Zhang, et al.
(författare)
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Making monolayer graphene photoluminescent by electron-beam-activated fluorination approach
- 2023
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- The past one and half decades have witnessed a tremendous development of graphene electronics, and the key to the success of graphene is its exceptional properties. The lacking of an inherent bandgap endows graphene with excellent electrical properties but considerably limits its applications in light-emitting and high-performance graphene-based devices. Herein, an approach for the direct writing of semiconducting and photoluminescent fluorinated graphene (C4F) patterns on monolayer graphene by an optimized electron-beam-activated fluorination technique is reported. A series of characterization approaches, such as atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to demonstrate the successful preparation of C4F for maskless lithography. Specially, a sharp and strong photoluminescence located at the purple light range of ∼380 nm was observed in C4F, demonstrating a desirable semiconducting nature, and the bandgap was further confirmed by follow-up electrical measurements, where the C4F filed-effect transistor exhibited a p-type semiconductor behavior and significantly enhanced on/off ratio. Therefore, this work provides a novel technique for the fabrication of graphene devices for promising electronic and optoelectronic applications, but also opens a route towards the tailoring and engineering of electronic properties of graphene.
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| 2. |
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| 3. |
- Duan, Tianbo, et al.
(författare)
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Electron-Beam-Induced Fluorination Cycle for Long-Term Preservation of Graphene under Ambient Conditions
- 2022
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- The aging in air inevitably results in the accumulation of airborne hydrocarbon contaminations on a graphene surface, which causes considerable difficulties in the subsequent application of graphene. Herein, we report an electron-beam-activated fluorination/defluorination cycle for achieving a long-term preservation of CVD graphene. After experiencing such cycle, the accumulation of airborne hydrocarbon on the graphene surfaces is strongly reduced, and the initial chemical status of graphene can be restored, which is confirmed by employing atomic force microscopy and X-ray photoelectron microscopy. Our reported approach provides an efficient method for the cleaning and long-term preservation of graphene, and it is particularly useful for graphene microscopy characterizations.
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| 4. |
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| 5. |
- Duan, Tianbo, 1992-
(författare)
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Functionalized Graphene as Superlattice and Gas Sensor
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Graphene, an atomic-thin carbon sheet with carbon atoms tightly packed honeycomb-like lattice, has attracted enormous interest due to its unique chemical and physical properties. However, the intrinsic zero bandgap characteristic of graphene has so far prevented graphene from building effective electronic and optoelectronic devices. To address this concern, different functionalization methods have been proposed to modify the electronic properties of graphene. This thesis focuses on different graphene surface functionalizations and their applications in gas detections and superlattices.First of all, the surface cleanness of graphene plays a crucial role in the performance of graphene devices. To achieve a controlled removal of polymer residues on graphene surface, a facile solvent based method has been proposed, which can drastically improve the charge carrier mobility of graphene devices by a factor of 3, indicating a potential ballistic transport of graphene under ambient condition. In addition, an electron beam induced fluorination cycle is proposed to eliminate the airborne hydrocarbon contamination related to aging effects on the graphene surface. Subsequent spectroscopic analysis confirms the long-term preservation of graphene using such technique. A similar technique, ion beam induced covalent functionalization has been used to locally fluorinate graphene, which could enhance the sensitivity of NH3 sensing as compared to a pristine graphene gas sensor by a factor of 8. The use of non-covalent, π-π stacking interactions for the functionalization of graphene opens a pathway to bind the functionalizing groups from nearly unlimited variety of p conjugated molecules. Here, we demonstrate that the use of BP2T molecules functionalizing graphene leads to an enhanced sensitivity to NH3 by a factor of 3 comparing with that of pristine graphene. This particle beam induced functionalization technique can be used for the fabrication of graphene superlattices. Here, a direct nanostructuring technique by employing electron beam induced etching with different precursor gases has been proposed to achieve localized structuring of graphene/hBN structures. Suspended fluorinated graphene can be obtained by using this dual-beam process, suggesting the capability of printing antidot superlattices where graphene would be suspended in a controllable way. When functionalizing a graphene bilayer by electron beam activated fluorination, a new type of moiré superlattice with rectangular periodicity can be formed due to the crystalline mismatch between the topmost fluorographene and underneath pristine graphene. Recently, rotational moiré superlattices of graphene were shown to be superconducting. We believe that this unique structure has the potential to equally reveal novel properties of 2D materials.
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| 6. |
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| 7. |
- Duan, Tianbo, 1992-, et al.
(författare)
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Towards Ballistic Transport CVD Graphene by Controlled Removal of Polymer Residues
- 2022
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 33:49, s. 495704-
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Tidskriftsartikel (refereegranskat)abstract
- Polymer-assisted wet transfer of chemical vapor deposited (CVD) graphene has achieved great success towards the true potential for large-scale electronic applications, while the lack of an efficient polymer removal method has been regarded as a crucial factor for realizing high carrier mobility in graphene devices. Hereby, we report an efficient and facile method to clean polymer residues on graphene surface by merely employing solvent mixture of isopropanol (IPA) and water (H2O). Raman spectroscopy shows an intact crystal structure of graphene after treatment, and the x-ray photoelectron spectroscopy indicates a significant decrease in the C–O and C=O bond signals, which is mainly attributed to the removal of polymer residues and further confirmed by subsequent atomic force microscopy analysis. More importantly, our gated measurements demonstrate that the proposed approach has resulted in a 3-fold increase of the carrier mobility in CVD graphene with the electron mobility close to 10 000 cm2 V−1 S−1, corresponding to an electron mean free path beyond 100 nm. This intrigues the promising application for this novel method in achieving ballistic transport for CVD graphene devices.
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| 8. |
- Li, Hu, 1986-, et al.
(författare)
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Direct writing of lateral fluorographene nanopatterns with tunable bandgaps and its application in new generation of moire superlattice
- 2020
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Ingår i: Applied Physics Reviews. - : American Institute of Physics. - 1931-9401. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- One of the primary goals for monolayer device fabrications and an ideal model of graphene as an atomic thin "canvas" is one that permits semiconducting/insulating lateral nanopatterns to be freely and directly drawn on the semimetallic graphene surface. This work demonstrates a reversible electron-beam-activated technique that allows direct writing of semiconducting/insulating fluorographene lateral nanopatterns with tunable bandgaps on the graphene surface with a resolution down to 9-15 nm. This approach overcomes the conventional limit of semiconducting C4F in the single-sided fluorination of supported graphene and achieves insulating C2F. Moreover, applying this technique on bilayer graphene demonstrates for the first time a new type of rectangular moire pattern arising from the generated C2F boat/graphene superlattice. This novel technique constitutes a new approach to fabricating graphene-based flexible and transparent electronic nanodevices with the CxF channels utilized as semiconducting or insulating counterparts, and also opens a route toward the tailoring and engineering of electronic properties of such materials in addition to the dominating triangular moire patterns from a graphene/hBN system.
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| 9. |
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| 10. |
- Li, Hu, 1986-, et al.
(författare)
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Fabrication of BP2T functionalized graphene via non-covalent π-π stacking interactions for enhanced ammonia detection
- 2021
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:57, s. 35982-35987
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Tidskriftsartikel (refereegranskat)abstract
- Graphene has stimulated great enthusiasm in a variety of fields, while its chemically inert surface still remains challenging for functionalization towards various applications. Herein, we report an approach to fabricate non-covalently functionalized graphene by employing pi-pi stacking interactions, which has potentialities for enhanced ammonia detection. 5,5 '-Di(4-biphenylyl)-2,2 '-bithiophene (BP2T) molecules are used in our work for the non-covalent functionalization through strong pi-pi interactions of aromatic structures with graphene, and systematic investigations by employing various spectroscopic and microscopic characterization methods confirm the successful non-covalent attachment of the BP2T on the top of graphene. From our gas sensing experiments, the BP2T functionalized graphene is promising for ammonia sensing with a 3-fold higher sensitivity comparing to that of the pristine graphene, which is mainly attributed to the enhanced binding energy between the ammonia and BP2T molecules derived by employing the Langmuir isotherm model. This work provides essential evidence of the pi-pi stacking interactions between graphene and aromatic molecules, and the reported approach also has the potential to be widely employed in a variety of graphene functionalizations for chemical detection.
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