| 1. |
- 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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| 2. |
- Sun, Jie, 1977, et al.
(author)
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Electrochemical Bubbling Transfer of Graphene Using a Polymer Support with Encapsulated Air Gap as Permeation Stopping Layer
- 2016
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In: Journal of Nanomaterials. - : Hindawi Limited. - 1687-4129 .- 1687-4110. ; 2016
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Journal article (peer-reviewed)abstract
- Electrochemical bubbling transfer of graphene is a technique with high industrial potential due to its scalability, time- and cost-effectiveness, and ecofriendliness. However, the graphene is often damaged due to the turbulence and the trapped bubbles formed by the direct H2O and H+ permeation through the supporting polymer. We invent a graphene mechanical support of polyethylene terephthalate foil/plastic frame/poly(methyl methacrylate) sandwich, with an encapsulated air gap as the permeation stopping layer. The graphene damage is drastically reduced, as confirmed by the morphology and structural and electrical characterization, ultimately improving the controllability/reproducibility of the bubbling transfer of graphene and other two-dimensional materials.
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| 3. |
- Xu, K., et al.
(author)
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GaN nanorod light emitting diodes with suspended graphene transparent electrodes grown by rapid chemical vapor deposition
- 2013
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:22, s. 5-
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Journal article (peer-reviewed)abstract
- Ordered and dense GaN light emitting nanorods are studied with polycrystalline graphene grown by rapid chemical vapor deposition as suspended transparent electrodes. As the substitute of indium tin oxide, the graphene avoids complex processing to fill up the gaps between nanorods and subsequent surface flattening and offers high conductivity to improve the carrier injection. The as-fabricated devices have 32% improvement in light output power compared to conventional planar GaN-graphene diodes. The suspended graphene remains electrically stable up to 300 degrees C in air. The graphene can be obtained at low cost and high efficiency, indicating its high potential in future applications.
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| 4. |
- Xu, K., et al.
(author)
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Graphene GaN-Based Schottky Ultraviolet Detectors
- 2015
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In: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 1557-9646 .- 0018-9383. ; 62:9, s. 2802-2808
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Journal article (peer-reviewed)abstract
- Graphene GaN-based Schottky ultraviolet detectors are fabricated. The monolayer graphene is grown by chemical vapor deposition. The graphene is much more transparent than metals, as confirmed by the fact that our devices retain their high responsivity up to 360-nm wavelength (corresponding to the band edge absorption of GaN). Importantly, by virtue of the tunable work function of graphene, the graphene GaN Schottky barrier height can be greatly enlarged. The built-in field is enhanced, and the detector performance is improved. The current ratio with and without luminescence is up to 1.6 x 10(4). The characteristic time constants of the devices are in the order of a few milliseconds. The device open-circuit voltage and short-circuit current are also increased. At last, special type Schottky devices consisting of GaN nanorods or surface-etched GaN are prepared for complementary study. It is found although the dry etching induced surface defects lead to an increase in the dark current, and these carrier traps also greatly contribute to the photoconductivity under luminescence, resulting in extraordinarily large responsivity (up to 360 A/W at -6 V).
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| 5. |
- Xu, K., et al.
(author)
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Graphene transparent electrodes grown by rapid chemical vapor deposition with ultrathin indium tin oxide contact layers for GaN light emitting diodes
- 2013
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:16
-
Journal article (peer-reviewed)abstract
- By virtue of the small active volume around Cu catalyst, graphene is synthesized by fast chemical vapor deposition (CVD) in a cold wall vertical system. Despite being highly polycrystalline, it is as conductive and transparent as standard graphene and can be used in light emitting diodes as transparent electrodes. 7-10 nm indium tin oxide (ITO) contact layer is inserted between the graphene and p-GaN to enhance hole injection. Devices with forward voltage and transparency comparable to those using traditional 240 nm ITO are achieved with better ultraviolet performances, hinting the promising future for application-oriented graphene by rapid CVD.
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| 6. |
- Xu, K., et al.
(author)
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ZnO nanorods/graphene/Ni/Au hybrid structures as transparent conductive layer in GaN LED for low work voltage and high light extraction
- 2016
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In: Solid-State Electronics. - : Elsevier BV. - 0038-1101. ; 126, s. 5-9
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Journal article (peer-reviewed)abstract
- In this paper, by virtue of one-dimensional ZnO nanorods and two-dimensional graphene film hybrid structures, both the enhanced current spreading and enhanced light extraction were realized at the same time. A 1 nm/1 nm Ni/Au layer was used as an interlayer between graphene and pGaN to form ohmic contact, which makes the device have a good forward conduction properties. Through the comparison of the two groups of making ZnO nanorods or not, it was found that the 30% light extraction efficiency of the device was improved by using the ZnO nanorods. By analysis key parameters of two groups such as the turn-on voltage, work voltage and reverse leakage current, it was proved that the method for preparing surface nano structure by hydrothermal method self-organization growth ZnO nanorods applied in GaN LEDs has no influence to device's electrical properties. The hybrid structure application in GaN LED, make an achievement of a good ohmic contact, no use of ITO and enhancement of light extraction at the same time, meanwhile it does not change the device structure, introduce additional process, worsen the electrical properties.
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