scholarly journals Layer-engineered large-area exfoliation of graphene

2020 ◽  
Vol 6 (44) ◽  
pp. eabc6601
Author(s):  
Ji-Yun Moon ◽  
Minsoo Kim ◽  
Seung-Il Kim ◽  
Shuigang Xu ◽  
Jun-Hui Choi ◽  
...  
Keyword(s):  
Large Scale ◽  
Metal Films ◽  
Thin Metal Film ◽  
Large Area ◽  
Exfoliated Graphene ◽  
Large Size ◽  
Measurement Analysis ◽  
Two Dimensional Materials ◽  
Mechanical Cleavage

The competition between quality and productivity has been a major issue for large-scale applications of two-dimensional materials (2DMs). Until now, the top-down mechanical cleavage method has guaranteed pure perfect 2DMs, but it has been considered a poor option in terms of manufacturing. Here, we present a layer-engineered exfoliation technique for graphene that not only allows us to obtain large-size graphene, up to a millimeter size, but also allows selective thickness control. A thin metal film evaporated on graphite induces tensile stress such that spalling occurs, resulting in exfoliation of graphene, where the number of exfoliated layers is adjusted by using different metal films. Detailed spectroscopy and electron transport measurement analysis greatly support our proposed spalling mechanism and fine quality of exfoliated graphene. Our layer-engineered exfoliation technique can pave the way for the development of a manufacturing-scale process for graphene and other 2DMs in electronics and optoelectronics.

scholarly journals Chlorosulfuric acid-assisted production of functional 2D materials

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Mohsen Moazzami Gudarzi ◽  
Maryana Asaad ◽  
Boyang Mao ◽  
Gergo Pinter ◽  
Jianqiang Guo ◽  
...  
Keyword(s):  
Hexagonal Boron Nitride ◽  
2D Materials ◽  
Real Life ◽  
Large Area ◽  
Polar Solvents ◽  
Aspect Ratios ◽  
Two Dimensional Materials ◽  
Liquid Phase Exfoliation

AbstractThe use of two-dimensional materials in bulk functional applications requires the ability to fabricate defect-free 2D sheets with large aspect ratios. Despite huge research efforts, current bulk exfoliation methods require a compromise between the quality of the final flakes and their lateral size, restricting the effectiveness of the product. In this work, we describe an intercalation-assisted exfoliation route, which allows the production of high-quality graphene, hexagonal boron nitride, and molybdenum disulfide 2D sheets with average aspect ratios 30 times larger than that obtained via conventional liquid-phase exfoliation. The combination of chlorosulfuric acid intercalation with in situ pyrene sulfonate functionalisation produces a suspension of thin large-area flakes, which are stable in various polar solvents. The described method is simple and requires no special laboratory conditions. We demonstrate that these suspensions can be used for fabrication of laminates and coatings with electrical properties suitable for a number of real-life applications.

a-Si TFT Technologies for AM-LCDS

1994 ◽  
Vol 345 ◽  
Author(s):  
Nobuki Ibaraki
Keyword(s):  
Implantation Technique ◽  
Picture Quality ◽  
Large Area ◽  
Aperture Ratio ◽  
Large Size ◽  
Ion Doping ◽  
Doping Technique ◽  
Future Technologies ◽  
Improved Characteristics

AbstractA technical trend for a-Si TFTs is their application to large-size, high-pixel density AMLCDs such as XGA, EWS, and HDTV. In order to realize these LCDs, the TFT device characteristics must be improved. Future technologies, which will be necessary to fabricate TFTs with improved characteristics are as follows,(1) Fully self-aligned TFT technology: A SA-TFT structure reduces the feedthrough voltage caused by parasitic capacitance due to gate/source overlap. This results in an improved picture quality and a higher aperture ratio. Fabrication of such a structure would require ion doping technology.(2) Ion doping technology: This non-mass-separated implantation technique has large area doping capability and much higher doping speed compared to conventional ion implantation technique. The major problems with the ion doping technique is the implantation of unwanted species which deteriorate the quality of source/drain and channel regions of TFTs.

scholarly journals Design and Demonstration of Large Scale Cu2O Photocathodes with Metal Grid Structure for Photoelectrochemical Water Splitting

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7422
Author(s):  
Min-Kyu Son
Keyword(s):  
Water Splitting ◽  
Large Scale ◽  
Grid Structure ◽  
Large Area ◽  
Intrinsic Conductivity ◽  
Metal Grid ◽  
Splitting System ◽  
Insight Into ◽  
Better Than

Upscaling of photoelectrode for a practical photoelectrochemical (PEC) water splitting system is still challenging because the PEC performance of large-scale photoelectrode is significantly low, compared to the lab scale photoelectrode. In an effort to overcome this challenge, sputtered gold (Au) and copper (Cu) grid lines were introduced to improve the PEC performance of large-scale cuprous oxide (Cu2O) photocathode in this work. It was demonstrated that Cu grid lines are more effective than Au grid lines to improve the PEC performance of large-scale Cu2O photocathode because its intrinsic conductivity and quality of grid lines are better than ones containing Au grid lines. As a result, the PEC performance of a 25-cm2 scaled Cu2O photocathode with Cu grid lines was almost double than one without grid lines, resulting in an improved charge transport in the large area substrate by Cu grid lines. Finally, a 50-cm2 scaled Cu2O photocathode with Cu grid lines was tested in an outdoor condition under natural sun. This is the first outdoor PEC demonstration of large-scale Cu2O photocathode with Cu grid lines, which gives insight into the development of efficient upscaled PEC photoelectrode.

Direct Synthesis of MoSe2 Thin Films on SiO2/Si Using Selenization Process of Sputtered Molybdenum

2020 ◽  
Vol 15 (5) ◽  
pp. 580-585
Author(s):  
Dae-Young Um ◽  
R. Nandi ◽  
Jeong-Hun Yang ◽  
Jin-Soo Kim ◽  
Jong-Woong Kim ◽  
...  
Keyword(s):  
Large Scale ◽  
Direct Synthesis ◽  
Cost Effective ◽  
Metal Films ◽  
Crystalline Quality ◽  
Research Attention ◽  
Molybdenum Diselenide ◽  
Potential Applications ◽  
Direct Current Sputtering

Recently, molybdenum diselenide (MoSe2) has attracted nascent research attention for potential applications in electronic and optoelectronic devices due to its unique properties including tunable bandgap, strong photoluminescence and large exciton binding energy. However, the synthesis of reproducible, controlled and large scale MoSe2 films is still a great challenge. Here, we have investigated the morphology, structure and crystalline quality of MoSe2 films synthesized by the selenization of Mo metal films. The Mo metal films of different thicknesses were deposited at room temperature by direct current sputtering. Subsequently, MoSe2 films were prepared by selenization of sputtered Mo films at 550 °C for 20 minutes. The obtained MoSe2 films are polycrystalline with hexagonal crystal structure. The crystalline quality of the MoSe2 films is improved with increase in the thickness of Mo metal films. The MoSe2 films are found to be n-type in nature and reasonably stoichiometric (Mo/Se ratio ∼1:1.9). This study provides an experimental demonstration of an alternative cost-effective direct synthesis of MoSe2 films on SiO2/Si for the applications of semiconductor devices.

Synchrotron X-ray Topography Studies of Epitaxial Lateral Overgrowth of GaN on Sapphire

1999 ◽  
Vol 572 ◽  
Author(s):  
Patrick J. Mcnally ◽  
T. Tuomi ◽  
R. Rantamaki ◽  
K. Jacobs ◽  
L. Considine ◽  
...  
Keyword(s):  
Quantum Well ◽  
Sapphire Substrate ◽  
Large Scale ◽  
Epitaxial Lateral Overgrowth ◽  
Large Area ◽  
X Ray ◽  
Lateral Overgrowth ◽  
Transmission Modes ◽  
Multi Quantum Well

ABSTRACTSynchrotron white beam x-ray topography techniques, in section and large-area transmission modes, have been applied to the evaluation of ELOG GaN on A12O3. Using the openings in 100 nm thick SiO2 windows, a new GaN growth took place, which resulted in typical overgrowth thicknesses of 6.8 μm. Measurements on the recorded Laue patterns indicate that the misorientation of GaN with respect to the sapphire substrate (excluding a 30° rotation between them) varies considerably along various crystalline directions, reaching a maximum of a ∼0.66° rotation of the (0001) plane about the [01•1] axis. This is ∼3% smaller than the misorientation measured in the non-ELOG reference, which reached a maximum of 0.68°. This misorientation varies measurably as the stripe or window dimensions are changed. The quality of the ELOG epilayers is improved when compared to the non- ELOG samples, though some local deviations from lattice coherence were observed. Long range and large-scale (order of 100 μm long) strain structures were observed in all multi quantum well epilayers.

Industrial-Scale Production of High-Quality Graphene Sheets by Millstone Grinders

2021 ◽  
Author(s):  
Peng Lv ◽  
Xiaoshi Li ◽  
Zihan Zhang ◽  
Biao Nie ◽  
Yiliang Wu ◽  
...  
Keyword(s):  
Large Scale ◽  
State Of The Art ◽  
The State ◽  
Industrial Scale ◽  
Graphene Sheets ◽  
Scale Production ◽  
Large Area ◽  
High Quality ◽  
Art Methods ◽  
Mechanical Cleavage

Abstract Graphene exhibits a variety of unprecedented innate properties and has sparked great interest in both fundamental science and regarding prospective commercial applications. To meet the ever-increasing demand for high-quality graphene sheets, an industrial-scale, reliable, environmental-friendly, low-cost production process is required. However, large-scale production high quality graphene remains elusive. Here we demonstrate a scalable mechanical cleavage method for large-quantity production of high quality large-area and few-layer graphene sheets by introducing a millstone grinding process. The average thickness of the graphene sheets is around 5 nm. This procedure is simpler than the state-of-the-art methods that allows for scalable preparation of graphene dispersion in hundreds of litres by mechanical cleavage of graphite, and the yield is 30-40%. The size of the prepared graphene sheets can be tuneable from few micrometres to tens of micrometres by varying the dimension of raw graphite, which is larger than that produced by the state-of-the-art methods. Moreover, comparing to conductive agents, the conductivity of wafers containing graphene can be increased by one order of magnitude, suggesting a high potential of the prepared graphene sheets for the application as conductive agent in lithium battery cathodes. This allows the requirements of different sizes graphene sheets for industry applications in different fields.

a-Si TFT Technologies for AM-LCDS

1994 ◽  
Vol 336 ◽  
Author(s):  
Nobuki Ibaraki
Keyword(s):  
Implantation Technique ◽  
Picture Quality ◽  
Large Area ◽  
Aperture Ratio ◽  
Large Size ◽  
Ion Doping ◽  
Doping Technique ◽  
Future Technologies ◽  
Improved Characteristics

ABSTRACTA technical trend for a-Si TFTs is their application to large-size, high-pixel density AM-LCDs such as XGA, EWS, and HDTV. In order to realize these LCDs, the TFT device characteristics must be improved. Future technologies, which will be necessary to fabricate TFTs with improved characteristics are as follows(1) Fully self-aligned TFT technology: A SA-TFT structure reduces the feedthrough voltage caused by parasitic capacitance due to gate/source overlap. This results in an improved picture quality and a higher aperture ratio. Fabrication of such a structure would require ion doping technology.(2) Ion doping technology: This non-Mass-separated implantation technique has large area doping capability and much higher doping speed compared to conventional ion implantation technique. The Major problems with the ion doping technique is the implantation of unwanted species which deteriorate the quality of source/drain and channel regions of TFTs.

scholarly journals Optimisation of processing conditions during CVD growth of 2D WS2 films from a chloride precursor

2022 ◽  
Author(s):  
William R. Campbell ◽  
Francesco Reale ◽  
Ravi Sundaram ◽  
Simon J. Bending
Keyword(s):  
Large Scale ◽  
Optical Quality ◽  
Dramatic Improvement ◽  
Large Area ◽  
Tungsten Disulphide ◽  
Wide Range ◽  
Polystyrene Support ◽  
Direct Band ◽  
Cvd Growth

AbstractMonolayer tungsten disulphide (WS2) is a direct band gap semiconductor which holds promise for a wide range of optoelectronic applications. The large-area growth of WS2 has previously been successfully achieved using a W(CO)6 precursor, however, this is flammable and a potent source of carbon monoxide (CO) upon decomposition. To address this issue, we have developed a process for the wafer-scale growth of monolayer WS2 from a tungsten hexachloride (WCl6) precursor in a commercial cold-wall CVD reactor. In comparison to W(CO)6, WCl6 is less toxic and less reactive and so lends itself better to the large-scale CVD growth of 2D layers. We demonstrate that a post-growth H2S anneal can lead to a dramatic improvement in the optical quality of our films as confirmed by photoluminescence (PL) and Raman measurements. Optimised films exhibit PL exciton emission peaks with full width at half maximum of 51 ± 2 meV, comparable to other state-of-the-art methods. We demonstrate that our WS2 films can be readily transferred from the sapphire growth substrate to a Si/SiO2 target substrate with no detectable degradation in quality using a polystyrene support layer. Our approach represents a promising step towards the industrial-scale fabrication of p-n junctions, photodetectors and transistors based on monolayer WS2.

scholarly journals SYNTHETIC GRAPHENE GROWN BY CHEMICAL VAPOR DEPOSITION ON COPPER FOILS

2013 ◽  
Vol 27 (10) ◽  
pp. 1341002 ◽  
Author(s):  
TING FUNG CHUNG ◽  
TIAN SHEN ◽  
HELIN CAO ◽  
LUIS A. JAUREGUI ◽  
WEI WU ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Large Scale ◽  
Rapid Development ◽  
Graphene Film ◽  
Single Layer ◽  
Chemical Vapor ◽  
Mechanical And Thermal Properties ◽  
Large Area ◽  
Exfoliated Graphene

The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interest. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties. There has been a growing need and rapid development in large-area deposition of graphene film and its applications. Chemical vapor deposition on copper has emerged as one of the most promising methods in obtaining large-scale graphene films with quality comparable to exfoliated graphene. In this paper, we review the synthesis and characterizations of graphene grown on copper foil substrates by atmospheric pressure chemical vapor deposition. We also discuss potential applications of such large-scale synthetic graphene.

Convergent Beam Electron Diffraction

1978 ◽  
Vol 36 (3) ◽  
pp. 304-315
Author(s):  
G. Lehmpfuhl
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Crystal Surface ◽  
Diffraction Spot ◽  
Crystal Thickness ◽  
Large Area ◽  
Electron Microscopic ◽  
Additional Information ◽  
Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

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