| 21. |
- Fu, Yifeng, 1984, et al.
(författare)
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Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
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Tidskriftsartikel (refereegranskat)abstract
- A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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| 22. |
- Guo, W. L., et al.
(författare)
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Process Optimization of Passive Matrix GaN-Based Micro-LED Arrays for Display Applications
- 2019
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 48:8, s. 5195-5202
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Tidskriftsartikel (refereegranskat)abstract
- Passive matrix GaN-based micro light-emitting diode (LED) arrays with two resolutions of 32 × 32 and 128 × 64 are designed and fabricated, and a micro control unit is used to drive the devices and display Chinese characters. The process of the micro-LED display arrays is systematically optimized, where emphasis has been put on solving two specific technical problems. First, the deep isolation trench is etched in two steps in order to decrease the slope of the isolation trench so as to ease the p electrode to “climb”. In this way, the otherwise easily broken p metal line is now very reliable. Second, a secondary growth method is employed to deposit SiO2 onto the n metal line as an insulation layer between the p and n electrode layers. Between the two deposition steps, the chips are rotated with a certain angle. Therefore, the probability of pinhole overlap is significantly reduced, and the insulation between the p and n electrode layers is guaranteed. Using the optimized micro-LED process, micro displays are fabricated and their electrical, optical, and thermal characteristics for two different pixel sizes are analyzed. Experiments show that the process optimization above helps realize the outstanding properties of the micro-LED display arrays, increase the device and system reliability. The work will contribute to the implementation of the GaN based micro-LED technologies in real life.
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| 23. |
- Guo, W., et al.
(författare)
-
Rapid chemical vapor deposition of graphene on liquid copper
- 2016
-
Ingår i: Synthetic Metals. - : Elsevier BV. - 0379-6779. ; 216, s. 93-97
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Tidskriftsartikel (refereegranskat)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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| 24. |
- Jiang, Bing-Xin, et al.
(författare)
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Fabrication and bonding of In bumps on Micro-LED with 8 μ m pixel pitch
- 2024
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Ingår i: ENGINEERING RESEARCH EXPRESS. - 2631-8695. ; 6:2
-
Tidskriftsartikel (refereegranskat)abstract
- Indium (In) is currently used to fabricate metal bumps on micro-light-emitting diode (Micro-LED) chips due to its excellent physical properties. However, as Micro-LED pixel size and pitch decrease, achieving high-quality In bumps on densely packed Micro-LED chips often presents more challenges. This paper describes the process of fabricating In bumps on micro-LEDs using thermal evaporation, highlighting an issue where In tends to grow laterally within the photoresist pattern, ultimately blocking the pattern and resulting in undersized and poorly dense In bumps on the Micro-LED chip. To address this issue, we conducted numerous experiments to study the height variation of In bumps within a range of photoresist aperture sizes (3 mu m -7 mu m) under two different resist thickness conditions (3.8 mu m and 4.8 mu m). The results showed that the resist thickness had a certain effect on the height of In bumps on the Micro-LED chip electrodes. Moreover, we found that, with the photoresist pattern size increasing under constant resist thickness conditions, the height and quality of the bumps significantly improved. Based on this finding, we rationalized the adjustment of the photoresist pattern size within a limited emission platform range to compensate for the height difference of In bumps caused by different resist thicknesses between the cathode and anode regions. Consequently, well-shaped and dense In bumps with a maximum height of up to 4.4 mu m were fabricated on 8 mu m pitch Micro-LED chips. Afterwards, we bonded the Micro-LED chip with indium bumps to the CMOS chip, and we found that we could successfully control the CMOS chip to drive the Micro-LED chip to display specific characters through the Flexible Printed Circuit (FPC). This work is of significant importance for the fabrication of In bumps on Micro-LED chips with pitches below 10 mu m and subsequent bonding processes.
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| 25. |
- Li, Kai, et al.
(författare)
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Metal thermopile infrared detector with vertical graphene
- 2023
-
Ingår i: Wuli Xuebao/Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 72:3
-
Tidskriftsartikel (refereegranskat)abstract
- Thermopile infrared detector is a kind of detector device mainly composed of thermocouple as the basic unit. Because of its simple principle, no need of cooling equipment, and other advantages, it has been widely used in various fields of production and life. However, the absorption rates of the materials in conventional thermopile devices are poor, and the majority of them are incompatible with microfabrication methods. In this work, a metal thermopile infrared detector with vertical graphene (VG) is designed and fabricated. The VG is grown via plasma enhanced chemical vapor deposition, and retained at the device’s thermal ends to provide the thermopile IR detector’s wideband and high response characteristics. The detector achieves a room temperature responsivity reaching a value as high as 1.53 V/W at 792 nm, which can increase the response results about 28 times and reduce the response time to 0.8 ms compared with the thermopile detector without VG. After systematically measuring the response results, it is finally found that there are three main mechanisms responsible for the response on the composite device. The first one is the response generated by the metal thermopile itself alone. The second one is the response increased eventually by the contribution of VG covered at the metal thermal junction that expands the temperature difference. The last one is the response generated by the temperature gradient existing inside the VG on the surface of the device after the absorption of heat. The portion of each partial response mechanism in the total response is also analyzed, providing a new reference direction for analyzing the response generation mechanism of thermopile detectors with other absorbing materials. The process is compatible with the microfabrication, while the device performance is enhanced and suitable for mass production. Furthermore, by utilizing the surface plasmon resonance to combine VG with metal nanoparticles, the material’ s light absorption is found to be enhanced significantly under the same conditions, and the resulting thermal voltage can be increased to 6 times. The results indicate that VG promises to possess practical applications, in many fields such as photoelectric sensing and power production devices. This technology provides a new method to manufacture high-performance thermopile infrared detectors and other sensor devices.
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| 26. |
- Li, S., et al.
(författare)
-
New Strategy for Black Phosphorus Crystal Growth through Ternary Clathrate
- 2017
-
Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7505 .- 1528-7483. ; 17:12, s. 6579-6585
-
Tidskriftsartikel (refereegranskat)abstract
- We are reporting a new synthetic strategy to grow large-sized black phosphorus (Black-P) crystals through a ternary clathrate Sn24P22-xI8, under lower synthetic temperature and pressure. The Black-P crystals are found grown in situ at the site where the solid clathrate originally resides, which suggests chemical vapor mineralizer does not play a critical role for the Black-P formation. More detailed systematical studies have indicated the P vacancies in the framework of the ternary clathrate Sn24P22-xI8 are important for the subsequent Black-P from phosphorus vapors, and a likely vapor solid solid model is responsible for the Black-P crystal growth. The obtained room temperature mobility mu is similar to 350 cm(2)/V.s from Hall measurements at mechanically cleaved flakes, where noticeable microcracks are visible. The obtained high mobility value further suggests the high quality of the Black-P crystals synthesized through this route.
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| 27. |
- Lindvall, Niclas, 1985, et al.
(författare)
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Towards transfer-free fabrication of graphene NEMS grown by chemical vapour deposition
- 2012
-
Ingår i: Micro and Nano Letters. - : Institution of Engineering and Technology (IET). - 1750-0443. ; 7:8, s. 749-752
-
Tidskriftsartikel (refereegranskat)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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| 28. |
- Lindvall, Niclas, 1985, et al.
(författare)
-
Transfer-free fabrication of suspended graphene grown by chemical vapor deposition
- 2012
-
Ingår i: 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems. NEMS 2012, Kyoto, 5 - 8 March 2012. - 9781467311243 ; , s. 19-22
-
Konferensbidrag (refereegranskat)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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| 29. |
- Liu, Lihui, 1985, et al.
(författare)
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A Mechanism for Highly Efficient Electrochemical Bubbling Delamination of CVD-Grown Graphene from Metal Substrates
- 2016
-
Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 3:8
-
Tidskriftsartikel (refereegranskat)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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| 30. |
- Liu, Lihui, et al.
(författare)
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Two-In-One Method for Graphene Transfer: Simplified Fabrication Process for Organic Light-Emitting Diodes
- 2018
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 10:8, s. 7289-7295
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene as one of the most promising transparent electrode materials has been successfully applied in organic light-emitting diodes (OLEDs). However, traditional poly(methyl methacrylate) (PMMA) transfer method usually results in hardly removed polymeric residues on the graphene surface, which induces unwanted leakage current, poor diode behavior, and even device failure. In this work, we proposed a facile and efficient two-in-one method to obtain clean graphene and fabricate OLEDs, in which the poly(9,9-di-n-octylfluorene-alt-(1,4-phenylene-(4-sec-butylphenyl)imino)-1,4-phenylene) (TFB) layer was inserted between the graphene and PMMA film both as a protector during the graphene transfer and a hole-injection layer in OLEDs. Finally, green OLED devices were successfully fabricated on the PMMA-free graphene/TFB film, and the device luminous efficiency was increased from 64.8 to 74.5 cd/A by using the two-in-one method. Therefore, the proposed two-in-one graphene transfer method realizes a high-efficient graphene transfer and device fabrication process, which is also compatible with the roll-to-roll manufacturing. It is expected that this work can enlighten the design and fabrication of the graphene-based optoelectronic devices.
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