| 21. |
- Li, S., et al.
(författare)
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New Strategy for Black Phosphorus Crystal Growth through Ternary Clathrate
- 2017
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7505 .- 1528-7483. ; 17:12, s. 6579-6585
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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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| 22. |
- Lindvall, Niclas, 1985, et al.
(författare)
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Towards transfer-free fabrication of graphene NEMS grown by chemical vapour deposition
- 2012
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Ingår i: Micro and Nano Letters. - : Institution of Engineering and Technology (IET). - 1750-0443. ; 7:8, s. 749-752
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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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| 23. |
- 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
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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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| 24. |
- 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
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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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| 25. |
- Liu, Lihui, et al.
(författare)
-
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
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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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| 26. |
- Liu, Q., et al.
(författare)
-
High responsivity sensing of unfocused laser and white light using graphene photodetectors grown by chemical vapor deposition
- 2016
-
Ingår i: Optical Materials Express. - 2159-3930. ; 6:7, s. 2158-2164
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene photodetectors grown by chemical vapor deposition are fabricated for unfocused laser and white light sensing. The unfocused light enlarges the illuminated graphene area and mimics the real-life sensing conditions, yielding a responsivity of 104 mA/W at room temperature without enhancing absorbance by waveguide and plasmonics. The devices are based on positive photoconductivity from the electron-hole photocarrier pairs and the bolometric-effect-induced negative photoconductivity. The buried off-center local gate induces a net internal potential in the graphene. The relative strength of the two photoconductivities depends on the gate voltage. The technology is scalable, which is a step ahead toward real applications.
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| 27. |
- Lockhart de la Rosa, César Javier, 1987, et al.
(författare)
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Frame assisted H2O electrolysis induced H2 bubbling transfer of large area graphene grown by chemical vapor deposition on Cu
- 2013
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:2
-
Tidskriftsartikel (refereegranskat)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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| 28. |
- Lu, Yu, et al.
(författare)
-
Electroless deposition of high-uniformity nickel microbumps with ultrahigh resolution of 8 μm pitch for monolithic Micro-LED display
- 2024
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001. ; 175
-
Tidskriftsartikel (refereegranskat)abstract
- Micro-light-emitting diode (Micro-LED) displays have attracted growing attention due to their unsurpassed properties that satisfy the requirements of reality/virtual reality (AR/VR) displays. A crucial procedure of monolithic integration technology in high-density microdisplays is the interconnection process, which is intimately associated with the quality of the display device. Microfluidic electroless interconnection (MELI), an innovative low-temperature and pressure-free chip-stacking approach that eliminates the warpage-induced issues and cracking damage of the chip caused by thermo-compression bonding (TCB), holds great promise as a technology for establishing interconnections between the CMOS driver and Micro-LED. However, the requirement for the consistency of the microbump arrays and the risk of creating bridges is significantly intensified with smaller gaps in stacked chips, which restricts the application range of MELI to high-density interconnects. This paper analyzes the feasibility of further lowering the stand-off height of stacked chips in ultrafine pitch interconnects by optimizing the bump preparation process. The plasma modification time and surfactant concentration during the bump preparation process have been investigated. The result indicated that microbump arrays with a uniformity of less than 3% could be successfully manufactured by employing a 7-min plasma treatment and incorporating optimal surfactants, which catalyzes the implementation of the subsequent vertical interconnection process and eventually enhances yields of Micro-LEDs.
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| 29. |
- Nam, Youngwoo, 1983, et al.
(författare)
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Graphene p-n-p junctions controlled by local gates made of naturally oxidized thin aluminium films
- 2012
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 50:5, s. 1987-1992
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Tidskriftsartikel (refereegranskat)abstract
- Graphene structures with both top- and bottom-electrostatic gates are studied. The top gate is made of thin aluminium (Al) film deposited directly onto graphene, with no prior dielectric layer in between. Natural oxidation of Al at the interface with graphene results in an insulating barrier proving useful in making top gates to graphene. For electrically disconnected top gate, graphene resistance as a function of the slowly-varying back-gate voltage shows hysteresis which reveals dielectric properties of the barrier. The estimated barrier thickness is only 2 nm allowing for very sharp profiles of the electric field in graphene devices. By applying voltages to both back- and top gates, effective p–n–p junctions with sharp interfaces can be created.
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| 30. |
- Nam, Youngwoo, 1983, et al.
(författare)
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Quantum Hall effect in graphene decorated with disordered multilayer patches
- 2013
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:233, s. 233110-
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum Hall effect (QHE) is observed in graphene grown by chemical vapour deposition using platinum catalyst. The QHE is even seen in samples which are irregularly decorated with disordered multilayer graphene patches and have very low mobility (
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