| 1. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Microwave characterization of Ti/Au-graphene contacts
- 2013
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:17, s. 173111-
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Journal article (peer-reviewed)abstract
- In this paper, we report on a microwave characterization of the interface between Ti/Au contacts and chemical vapor deposition graphene using structures of Corbino geometry, with primary focus on extracting and modeling the capacitance associated with the contact region. It is found that with the current contact resistivity, ρc∼10^−6 Ωcm2, the contact capacitance, on the order Cc∼1 μF/cm2, has a negligible effect on microwave transmission through the contact below ∼100 GHz. Finally, a parallel plate capacitance model for the contact is presented.
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| 2. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Towards Graphene Electrodes for High Performance Acoustic Resonators
- 2013
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In: WOCSDICE. ; , s. 99-100
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Conference paper (peer-reviewed)abstract
- The tunable FBAR is a promising building block for versatile microwave systems. Utilizing graphene electrodes promises higher tunability and frequency. Increased parasitic resistance may hamper the Q-factor of the resonator. This paper reports the initiated study of graphene and contacts at DC and microwave frequencies for optimization of these parameters leading to graphene FBARs.
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| 3. |
- Buron, J.D., et al.
(author)
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Correlation between THz AC and micro-four-point-probe DC conductivity mapping of graphene sheets
- 2012
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In: Laser and Tera-Hertz Science and Technology, LTST 2012. - Washington, D.C. : OSA.
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Conference paper (peer-reviewed)abstract
- We present quantitative correlation mapping of the sheet conductance of large areas of graphene. Terahertz time-domain spectroscopy (THz-TDS) maps the nanoscale conductance averaged over the beam spot size whereas micro four-point probe (M4PP) maps the micro-scale conductance.
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| 4. |
- Buron, J. D., et al.
(author)
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Graphene Conductance Uniformity Mapping
- 2012
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:10, s. 5074-5081
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Journal article (peer-reviewed)abstract
- We demonstrate a combination of micro four-point probe (M4PP) and non-contact terahertz time-domain spectroscopy (THz-TDS) measurements for centimeter scale quantitative mapping of the sheet conductance of large area chemical vapor deposited graphene films. Dual configuration M4PP measurements, demonstrated on graphene for the first time, provide valuable statistical insight into the influence of microscale defects on the conductance, while THz-TDS has potential as a fast, non-contact metrology method for mapping of the spatially averaged nanoscopic conductance on wafer-scale graphene with scan times of less than a minute for a 4-in. wafer. The combination of M4PP and THz-TDS conductance measurements, supported by micro Raman spectroscopy and optical imaging, reveals that the film is electrically continuous on the nanoscopic scale with microscopic defects likely originating from the transfer process, dominating the microscale conductance of the investigated graphene film.
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| 5. |
- Evelt, M., et al.
(author)
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Chiral charge pumping in graphene deposited on a magnetic insulator
- 2017
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:2
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Journal article (peer-reviewed)abstract
- We demonstrate experimentally that a sizable chiral charge pumping can be achieved at room temperature in graphene/yttrium iron garnet (YIG) bilayer systems. The effect, which cannot be attributed to the ordinary spin pumping, reveals itself in the creation of a dc electric field/voltage in graphene as a response to the dynamic magnetic excitations (spin waves) in an adjacent out-of-plane magnetized YIG film. We show that the induced voltage changes its sign when the orientation of the static magnetization is reversed, clearly indicating the broken mirror reflection symmetry about the planes normal to the graphene/YIG interface. The strength of effect shows a nonmonotonous dependence on the spin-wave frequency, in agreement with the proposed theoretical model.
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| 6. |
- Guo, W., et al.
(author)
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Rapid chemical vapor deposition of graphene on liquid copper
- 2016
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In: Synthetic Metals. - : Elsevier BV. - 0379-6779. ; 216, s. 93-97
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Journal article (peer-reviewed)abstract
- Molten copper is used to catalyze the graphene synthesis by chemical vapor deposition. The Cu has no grains above melting temperature, which is favorable for graphene growth. Using a vertical cold wall system, the deposition rate is drastically increased as compared with common hot-wall tube furnaces, pushing the method one step forward towards applications. A molybdenum-graphite Joule heater is used to avoid mechanical deformation of the carrier foil for the catalyst to ease the subsequent processes. The rapid deposition makes it possible to observe graphene growth on liquid Cu even at low pressure, where severe Cu evaporation simultaneously occurs.
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| 7. |
- Lindvall, Niclas, 1985, et al.
(author)
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Towards transfer-free fabrication of graphene NEMS grown by chemical vapour deposition
- 2012
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In: Micro and Nano Letters. - : Institution of Engineering and Technology (IET). - 1750-0443. ; 7:8, s. 749-752
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Journal article (peer-reviewed)abstract
- Graphene, an atomic monolayer of sp(2)-hybridised carbon atoms, is a promising material for future NEMS based on its remarkable electronic and mechanical properties. Through the rapid progress of chemical vapour deposition of large-scale, high-quality graphene, these applications seem to be close to reality. However, issues related to the graphene transfer process limit the reproducibility of such devices. In this Letter, the authors present two different approaches for fabricating suspended graphene devices without any transfer step, using both catalytically and non-catalytically grown graphene. The authors achieve high reproducibility in manufacturing flat and uniform suspended graphene beams. While good mechanical properties are observed, the electrical performance is still poor, requiring improvements.
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| 8. |
- Lindvall, Niclas, 1985, et al.
(author)
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Transfer-free fabrication of suspended graphene grown by chemical vapor deposition
- 2012
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In: 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems. NEMS 2012, Kyoto, 5 - 8 March 2012. - 9781467311243 ; , s. 19-22
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Conference paper (peer-reviewed)abstract
- Graphene, a true two-dimensional material with extraordinary mechanical- and electronic properties, is thought to be ideal for nanoelectromechanical systems (NEMS), like mass- and force sensors. Here, we present two different ways to fabricate suspended graphene for the intended use in future NEMS applications. The fabrication schemes do not require transfer of graphene from a catalyst where the graphene is grown on to another supporting substrate. The transfer is a source of several issues causing irreproducibility in large-scale production of graphene devices. We obtain suspended graphene membranes by locally removing the copper thin film on top of which the graphene is catalytically grown. The membranes are uniform and exhibit mechanical properties similar to those of exfoliated graphene. Also, suspended graphene beams with electrical interconnects are fabricated from non-catalytically grown graphene on SiO 2. Both approaches represent the first steps towards transfer-free fabrication of suspended graphene for NEMS applications.
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| 9. |
- Liu, Lihui, 1985, et al.
(author)
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A Mechanism for Highly Efficient Electrochemical Bubbling Delamination of CVD-Grown Graphene from Metal Substrates
- 2016
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In: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 3:8
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Journal article (peer-reviewed)abstract
- In most cases, transfer of chemical-vapor-deposited 2D materials from metallic foil catalysts onto a target substrate is the most necessary step for their promising fundamental studies and applications. Recently, a highly efficient and nondestructive electrochemical delamination method has been proposed as an alternative to the conventional etching transfer method, which alleviates the problem of cost and environment pollution because it eliminates the need to etch away the metals. Here, the mechanism of the electrochemical bubbling delamination process is elucidated by studying the effect of the various electrolytes on the delamination rate. A capacitor-based circuit model is proposed and confirmed by the electrochemical impedance spectroscopy results. A factor of 27 decrease in the time required for complete graphene delamination from the platinum cathodes is found when increasing the NaOH ratio in the electrolyte solution. The opposite trend is observed for delamination at the anode. The surface screening effect induced by nonreactive ions in the vicinity of the electrodes plays a key role in the delamination efficiency. The analysis is generic and can be used as a guideline to describe and design the electrochemical delamination of other 2D materials from their metal catalysts as well.
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| 10. |
- Lockhart de la Rosa, César Javier, 1987, et al.
(author)
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Frame assisted H2O electrolysis induced H2 bubbling transfer of large area graphene grown by chemical vapor deposition on Cu
- 2013
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:2
-
Journal article (peer-reviewed)abstract
- An improved technique for transferring large area graphene grown by chemical vapor deposition on copper is presented. It is based on mechanical separation of the graphene/copper by H-2 bubbles during H2O electrolysis, which only takes a few tens of seconds while leaving the copper cathode intact. A semi-rigid plastic frame in combination with thin polymer layer span on graphene gives a convenient way of handling-and avoiding wrinkles and holes in graphene. Optical and electrical characterizations prove the graphene quality is better than that obtained by traditional wet etching transfer. This technique appears to be highly reproducible and cost efficient.
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