NL2010216C2

NL2010216C2 - Synthesizing and transferring at least one large layer of graphene.

Info

Publication number: NL2010216C2
Application number: NL2010216A
Authority: NL
Inventors: Guido Cornelis Antonius Maria Janssen; Shou-En Zhu
Original assignee: Univ Delft Tech
Priority date: 2013-01-31
Filing date: 2013-01-31
Publication date: 2014-08-04

Description

Short title: Synthesizing and transferring at least one large

layer of graphene DESCRIPTION FIELD OF THE INVENTION

5 The present invention is in the field of graphene synthesis and transfer of at least one relatively large layer.

BACKGROUND OF THE INVENTION

Graphene is carbon comprising material. Its structure relates to one-atom-thick planar sheets of sp2-bonded carbon atoms that are 10 crystallographically densely packed in a honeycomb crystal lattice. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together.

It can be a basic building block for graphitic materials of all other dimensionalities. It can be wrapped up into fullerene, rolled 15 into ID carbon nanotubes or stacked into 3D graphite.

Graphene has attracted a lot of research interest because of its promising electronic applications related to its superior electron mobility, mechanical strength and thermal conductivity. It may have wide range of applications, for instance, field-effect transistors, 20 photonic or optoelectronic device, as a gas or liquid membrane, sequencing DNA through nano-holes in graphene etc. Graphene macroscopic samples have unusual properties such as a bipolar-transistor effect, ballistic transport of charges, large quantum oscillations, etc.

25 Various production methods of graphene are reported. Graphene or ultra-thin graphitic layers can be epitaxially grown on various substrates. (Single crystal) Graphene produced by (mechanical) exfoliation was a very expensive material. Since then, exfoliation procedures have been scaled up. It is noted that the price of 30 epitaxial grown graphene on e.g. SiC is dominated by the substrate price. Graphene has been produced by transfer from nickel, copper, gold, iridium, etc., and alloys thereof, though graphene on iridium is slightly rippled.

It remains however difficult to obtain high quality and clean 35 graphene e.g. in a device. Compared to monolayer graphene, crystallized multilayer graphene has stronger mechanical properties and higher conductivity. Such graphene is still transparent under the optical microscope and electron microscopy, and has high potential in the field of nano-imaging technology. It remains also 40 difficult to transfer graphene such that the quality and integrity 2 thereof are maintained at a high standard, which is crucial for the characteristics of graphene. The prior art graphene is not clean, has lots of contamination and cracks.

For graphene transfer from copper or other metal surface 5 various methods may be used.

For instance a dry transfer method may be used. Therein, the graphene is directly detached from a metal surface by applying an external force, such as a PDMS stamp or a thermal release tape.

However, the quality of graphene obtained is not good, as there are 10 lots of cracks or defect generated during the transfer processes.

For instance a wet transfer method may be used. Therein metal used is removed by an etching process; as a result graphene is floating on a liquid surface, typically an aqueous surface, with support plastic or glass slide substrate. This method typically also 15 needs a support film to transfer graphene from one liquid (solution) to another (location). During the transfer, the graphene is prone to stretching by the rigid (plastic or glass) substrate, and the substrate always contains lots of external contaminations. So, this method has various drawbacks: Introduction of external particles and 20 contaminations; Generation of strong strain on the graphene, the graphene films may tear and form residual stress and cracks. The transferred graphene contains lots of bubbles, which makes the quality of graphene at least one order of magnitude lower; the graphene obtained is difficult to handle. The graphene sometimes can 25 be attached directly to the plastic or glass substrate. Then is it impossible to separate them anymore.

Various documents recite graphene synthesis, especially epitaxial growth on metal substrates.

Qingkai Yu et al, in "Control and characterization of 30 individual grains and grain boundaries in graphene grown by chemical vapor deposition." Nature Materials, 2011, 10, pp 443-449, used copper as substrate, and a quartz tube hot wall furnace to synthesis graphene. Single hexagonal graphene crystals were achieved with controllable patterning and high temperature growth under ambient 35 pressure condition at 1050 °C. However, the graphene crystal size · was limited to tens of micrometers due to a bad control of the process .

Xuesong Li et al, in "Large-Area Graphene Single Crystals Grown by Low-Pressure Chemical Vapor Deposition of Methane on 40 Copper", J. Am. Chem. Soc., 2011, 133, pp 2816-2819, used a folded 3 copper foil as substrate to grow graphene under very low pressure condition (with a methane flow rate of 0.5 seem corresponding to partial pressure of 8 mTorr) at 1035 °C with a quartz tube hot wall furnace. The graphene size up to 0.5 mm was achieved within 90 min.

5 However, under the conditions used the results obtained are non-reproducible .

Hong Wang et al, in "Controllable Synthesis of Submillimeter Single-Crystal Monolayer Graphene Domains on Copper Foils by Suppressing Nucleation", J. Am. Chem. Soc., 2012, 134, pp 3627-3630, 10 used a copper foil as substrate to grow sub-millimeter graphene under ambient conditions. A large amount of hydrogen gas (500 seem) was used to suppress the nucleation of graphene. However, the graphene obtained had a rectangular shape, and the quality of graphene was bad, it could be damaged easily.

15 Takayuki Iwasaki et al, in "Long-Range Ordered Single-Crystal

Graphene on High-Quality Heteroepitaxial Ni Thin Films Grown on MgO(lll)", Nano Lett., 2011, 11, pp 79-84, used a Ni thin film to growth large single crystal graphene on MgO (111) single crystal substrate. This method however is unsuitable for mass production.

20 Libo Gao et al, in "Repeated growth and bubbling transfer of graphene with millimetre-size single-crystal grains using platinum", Nature Communications 2012, 3, 699, grow graphene on a platinum foil substrate in a quartz tube hot furnace at 1000 °C. This method however is unsuitable for mass production.

25 It is noted that various methods relating to synthesizing other carbon comprising molecules, such as carbon nanotubes, are known. These methods typically are not applicable for obtaining graphene.

A drawback of prior art methods is that the quality of the 30 graphene obtained is not very good, e.g. it may contain many dislocations. Further it is difficult to grow a large area of graphene layers, especially of good quality. Typically when obtaining graphene after growth thereof it is cumbersome to separate graphene, such as by removing a supporting layer. It is noted that 35 various techniques, e.g. PECVD, result in poor quality graphene. It is also a drawback that prior art systems are not very costs effective, e.g. as synthesis consumes relatively large amounts of energy, are performed at relative high temperatures (1000 °C or higher), etc. As a consequence also characteristics of a graphene 4 layer are not very good, e.g. in terms of being impermeable to gas and liquid, in terms of homogeneity, in terms of conductivity, etc.

Manufacturing and transfer of a high quality mono- or multilayer of crystalline graphene, specially a low defect density and 5 clean film thereof, has not been reported to the knowledge of inventors , .

The present invention therefore relates to method of forming a high quality graphene film, a high quality graphene film, and a device comprising said layer, which overcomes one or more of the 10 above disadvantages, without jeopardizing functionality and advantages .

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a method for synthesizing at least one large layer of graphene, such as a 15 mono-layer or a multi-layer of graphene. The layer is also referred to as a film throughout the description, i.e. a graphene structure having one or more layers.

It is noted that graphene obtained can relate to one mono layer, to a bi-layer, to a tri-layer, and to thicker stacks.

20 The synthesis comprises providing a support, the support comprising a first catalytic metal surface. The support may be consisting of the metal only, or comprising a metal layer on top of an other material, the other material preferably being an inert material. The support may comprise one or more materials, e.g. stacked as 25 (multi)layers. The surface provides catalytic action. In order to improve the action of the surface a surface roughness and/or impurity level of the support surface is reduced.

Also a carbon source, a hydrogen source, and an inert carrier gas, are provided, making the carbon available, and forming 30 graphene. Typically the carbon source is introduced into the conditioned environment at a pressure of less than 1000 Torr and at a flow rate of less than 500 seem. Graphene is then synthesized from carbon upon activation by the catalyst during a predetermined period thereby forming at least one layer of graphene conformally on the 35 catalytic surface

Typically decomposition of the carbon source takes place at certain process conditions, e.g. temperature, pressure, time, power, etc., whereas synthesis of graphene takes place at other process conditions, e.g. at a lower temperature. As mentioned above 5 synthesis is typically supported by presence of a catalytic material, such as a metal.

It has been found experimentally that graphene can be formed as a conformal layer, i.e. forming a more or less uniform layer with 5 respect to thickness. It is noted that during formation of a crystallographic material, such as graphene, a growth process may involve defects, dislocations and topographical effects, such as a slope. In other words, on a microscopic scale some non-uniformity may still exist.

10 As such decomposition and synthesizing preferably take place in a well-conditioned environment, the environment being adaptable in view of required process conditions, and the environment being extremely clean. Even more preferable the environment can be used for all or many of the present (optional) method steps. The 15 environment preferably is a vacuum chamber, such as a CVD chamber, a PVD chamber, and combinations thereof.

The present invention provides amongst others the advantage that in principle any microscopic or nanoscopic graphene-structure can be formed, by conformal growth. Therein graphene uniformly 20 covers the surface. It is noted that a conformal grown graphene layer is preferred, though a less conformal grown (e.g. directional) may be adequate for specific purposes.

It is noted that hydrogen can be added as active gas precursor in order to improve deposition of carbon. In general cooling between 25 a step of providing carbon and a step of synthesizing graphene takes place at a certain rate. The plasma can be used to further reduce the synthesis temperature. Thereby a well controllable graphene layer is provided of excellent quality, e.g. in terms of integrity, dislocation density, electrical properties, gas and liquid 30 (im)permeability, etc. Further the layer can be removed well from the support.

Typically decomposition and synthesis take place during a period of time. The present method is considered rather quick and efficient.

35 The present invention further provides high quality graphene. In an embodiment the electron mobility is larger than over 65,000 cm2/Vs. That is the highest CVD graphene mobility reported until now. In a preferred embodiment 100,000 cm2/Vs is obtained, e.g. by improving a clean step.

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Thereby the present invention provides a solution to one or more of the above mentioned problems.

Advantages of the present description are detailed throughout the description.

5 DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a method for synthesizing at least one large layer of graphene according to claim 1.

In an example the support is a container, preferably a 10 container from one single metal, such as copper, the container protecting the catalytic surface from environmental influences, such as impurities and particles, such as Si02. A typical length of the present container is from 1 mm to 600 mm, preferably from 1 mm to 120 mm; a width of 1 mm to 300 mm, such as 1 mm to 100 15 mm; and a height of 1 mm to 150 mm, such as 1 mm to 50 mm.

In an example the catalytic surface is accessible for the carbon source and hydrogen source, such as by providing an opening, or pores, or a membrane in the container, allowing passage of chemical reactants and preventing environmental 2 0 influences .

In principle a metal catalyst may provide the present advantages. However, it is important to clean a surface of the metal catalyst and reduce the surface roughness thereof and/or reduce an impurity level thereof. Surface roughness, often 25 shortened to roughness, is a measure of texture of a surface. It is typically quantified by vertical deviations of a real surface from an ideal (perfect flat) form. If these deviations are large, the surface is rough; if they are small the surface is smooth. Surface roughness can be determined with a profilometer. The 30 present surface is typically flat over a range of about 100 by 100 nm2. With the present method an especially with copper a sufficient flatness can be obtained, such as by chemical (pre-) etching of a surface.

Suitable metals are one or more of nickel, copper, cobalt, 35 iron, palladium, platinum, molybdenum, and alloys thereof.

However copper is preferred, e.g. in view of catalytic activity, small surface roughness, compatibility with the present method, etc .

In an example the catalyst surface is from 0.1 μτη- 0.5 mm 40 thick, such as from 0.5 μηα- 0.1 mm.

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In an example the support may comprise domains of a second material, such as of BN, quartz, mica and combinations thereof, wherein the domains are preferably selected from flake, single crystal, film, and combinations thereof. Such is advantageous in 5 view of optional further use of graphene, e.g. in terms of integration .

In an example the carbon source comprises pure C12 or comprises pure C13. As such pure C12 or pure C13 graphene may be obtained. The at least one graphene layer may be at least 99,5 % pure, preferably at 10 least 99,9 % pure, and in case of C12 more preferably at least 99,99 % pure, such as 99,999% pure. Such is very advantageous as for instance electrical and chemical properties of very pure graphene are more predictable and more constant.

In an example the carbon source is selected from benzene, methane, 15 ethane, ethylene, propane, and combinations thereof. Preferred are methane, ethane, and ethylene.

In an example the carrier gas is an inert gas, such as a noble gas, such as He, Ne, Ar, Kr, preferably Ar.

In an example the hydrogen source is H2.

20 In an example in step b) the surface is treated with a diluted carboxylic acid, the carboxylic acid being free of elements other than C, H and 0, such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid,- oxalic acid, and benzoic acid,

In an example a pH is from 1,5-6, preferably from 2-5, more 25 preferably from 2,5-3, that is relatively acidic. Thereby a pristine surface, such as of copper, is obtained.

In an example during treating the surface a temperature is increased, preferably to a temperature of 50-150 °C, more preferably to a temperature of 60-90 °C, such as from 70-80 °C. Thereby a 30 pristine surface, such as of copper, is obtained.

In an example the surface is treated during a period of time from 5 minutes to 4 hours, preferably from 10 minutes - 1 hour, such as from 15 minutes-30 minutes. Such is found sufficient.

In an example a solvent for the acid is water or an alcohol being 35 free of elements other than C, H and 0, such as methanol and ethanol.

In an example the surface is annealed at a temperature from (Tmelt-200) °C - (Tmeit-1) °C, preferably from (Tmeit-7 0) °C - (Traait-5) °C, more preferably from (Tmelt-50) °C - (Tmeit_10) °C, such as from 40 (Tmelt—20) °C - (Tmeit-15) °C. Preferably the surface is not heated too 8 much. It has been found that a temperature below the melt temperature and high enough provides the best result e.g. in terms of surface roughness and impurity levels.

In an example the surface is annealed during a period of time 5 from 5 minutes to 4 hours, preferably from 10 minutes - 2 hours, such as from 15 minutes-60 minutes.

In an example the conditioned environment is a vacuum chamber, such as a quartz chamber and a stainless steel chamber.

In an example the pressure inside the chamber is from 10~10 -10 10+3 Torr, preferably from 1CT5 - 10~2 Torr, that is relatively low.

In an example the flow rate of the carbon source is from 0,01-500 seem, preferably from 0,02-300 seem, more preferably from 0,1-50 seem, even more preferably from 0,5-20 seem, such as from 1-10 seem. Preferably the flow rate is more or less constant over time.

15 In an example a hydrogen flow rate is from 0,5-1500 seem, preferably from 1-500 seem, more preferably from 2-100 seem, even more preferably from 5-50 seem, such as 10-20 seem.

In an example decomposing and synthesizing is performed during a period of time from 1 minutes to 24 hours, preferably from 5 20 minutes - 12 hours, more preferably from 10 minutes - 4 hours, such as from 15 minutes- 2 hours.

In an example decomposing takes place by increasing the temperature in the conditioned environment, preferably to 400-1600 °C, more preferably to 600-1200 °C, such as 900-1080 °C.

25 In an example synthesizing graphene takes place during decomposition.

In an example a heating rate is from 10 °C - 500 °C/min., such as 20 °C - 300 °C/min..

In an example a cooling rate is from 10 °C - 500 °C/min, such as 20 30 °C - 300 °C/min.

The fast heating and cooling rate is provided by moving the furnace or moving the (sample) container, and by keeping the sample away from the heating zone.

In an example after step e) in step f) the one or more 35 conformal graphene layers are transferred to a release layer, such as by applying a release layer on the one or more conformal graphene layers .

In an example after step f) in step g) removing one or more of a sacrificial layer, such as by a chemical etch process, and 40 removing the catalyst comprising surface, such as by a chemical etch 9 process, such as by a solution of (NH4)2S208 or FeCl3. Therewith a free graphene layer is obtained.

In an example the release layer is applied as a fluid and is allowed to solidify, preferably by spin coating and/or by 5 evaporating a solvent.

In an example the release layer comprises one or more of an organo silicon compound, such as CH3[Si (CH3)2O]nSi(CH3)3 (PDMS), a polymer, such as PMMA, polyimide, polyamide, polycarbonate, a resin, such as a (meth)acrylate resin, such as polymers or copolymers of 10 methyl (meth)acrylate or other acrylic monomers, and epoxy, such as SU-8, and a natural or artificial rubber.

In an example the release layer has a Tgiass of 25-200 °C, more preferably of 30-120 °C, even more preferably of 40-90 °C, such as from 40-60 °C. It has been found experimentally that if graphene is 15 in contact with a material with a glass transition temperature, the graphene can be released easily, and at the same time maintain its characteristics. Preferably the transition temperature of the material is not too high.

With the above release layers optimal release of graphene is 20 obtained, e.g. in terms of integrity, cleanness, impurity levels, surface roughness, etc.

In an example a frame is provided on the release layer for supporting transfer thereof. Therewith the release layer can be handled easy. The frame may be from any suitable material and any 25 size, suited for the purpose.

In an example the release layer and at least one graphene layers are transferred to a receiving surface comprising one or more of Si, Si02, Si3N4, BN, mica, quartz, glass, polymer, rubber.

In an example the transfer further comprises aligning of the at 30 least one graphene layers and receiving surface, such as by providing one or more of an alignment marker on the receiving surface, an optical microscope, a means for rotating the receiving surface, a means for in plane movement of the receiving surface, and a means for tilting the receiving surface. In view of precise 35 positioning in specific cases alignment is desired.

In an example the release layer is heated to a temperature above the Tglass thereof, such as 5 -8 0 °C above Tglass, during a period of time of 5 minutes - 200 hours, such as 10 minutes-50 hours, at a reduced pressure, such as at a pressure from 10~10 - 10+3 Torr, 40 preferably from 10“8 - 10“° Torr. Such heating at a reduced pressure 10 may assist cleaning and annealing of a graphene layer. Therewith graphene and the release layer can be separated easy, while maintaining the advantageous characteristics of the graphene. After removal of the release layer, further annealing from e.g. 250 to 700 5 °C in 10"8 - 10~2 Torr or 1% to 50% partial pressure H2 in inert gas environment is optional to further improve graphene surface cleaning.

In a second aspect the present invention relates to at least one large layer of graphene, according to claim 9. The at least one 10 layer may have dimension from a few micrometers by a few micrometers up to a few centimeters by a few centimeters, such as 5 by 5 cm2. In principle the present technique makes synthesizing of even much larger layers possible, such as of a 200-500 cm2.

A single crystal graphene layer(s) can be obtained with the 15 present method, having in principle any desired shape, which can e.g. be stored for a long period of time without deterioration, such as by oxidation. In principle the present graphene can be stored for month, if not for years. Also the graphene can be transported and transferred with a much higher chance of obtaining fully intact 20 graphene thereafter.

A huge advantage of the present invention is that very pure graphene layers can be obtained. Prior art graphene typically comprises a (natural occurring) combination of C12 and C13. Such a combination of carbon isotopes influences the characteristics of 25 graphene obtained negatively, such as an increased power consumption if used in an electrical device. Providing (almost) pure C12 and pure C13 overcomes many technical problems of the prior art in this respect. The present at least one graphene layer is at least 99,5 % pure, preferably at least 99,9 % pure, and in case of C12 more 30 preferably at least 99,99 % pure, such as 99,999% pure.

The present graphene is of high quality, e.g. in terms of defects present on the at least one graphene layer. Defects may relate to particles, dislocations, disordered crystal structure, opens, etc. A defect density of less than 10-1 defects/cm2, 35 preferably less than 10"3 defects/cm2, more preferably less than 5*10~4 defects/cm2, even more preferably less than 1CT4 defect/cm2 is provided. Particle sizes involved are from 50 nm diameter and larger.

The present invention relates in a third aspect to a device 40 according to claim 10, such as one or more of a microfluidic device, 11 an implant, a semiconductor device, quantum spintronics, a transistor, a resistor, a coil, a diode, a conducting part, a chip, a TEM support membrane, a particle or gas filter membrane, a biochemical sensor, a micro or nano electro-mechanical systems device, 5 an optical coating, and an anti-oxidation coating.

In a fourth aspect the present invention relates to at least one large layer of graphene according to the invention or obtainable by a method according to the invention, on a optionally perforated membrane, such as a silicon nitride, silicon, hexagonal boron 10 nitride film, and Si02 membrane, optionally with at least one contact electrode, preferably an Au, a Cr, a Pt, a W, a Pd and a Mo electrode, the electrode preferably capable of one or more of TEM imaging, chemical sensing, biosensing, infrared or microwave laser mode lock application, flow cell and fluid cell application, such as 15 micro or nano fluidic cell and biochemical fluid cell, and antioxidation application, and/or wherein the graphene is a patterned graphene resistor wire, such as one or more of for micro or nano heating, and strain sensing in a pressure sensor application, and/or 20 wherein graphene is on or in between a hexagonal boron nitride film with e.g. an electrode either underneath boron nitride or on top of boron nitride for use in one or more of a transistor, a spintronics, pn junction, photocurrent detector, and a super computer application.

25 As such a vast range of applications is available by the present graphene layer(s). Relevant details of these applications are typically known to the person skilled in the art, or can be obtained through routine tests.

It is noted that implants, chips, etc. can be coated with 30 graphene, wherein graphene is a compound being biocompatible for a human or animal body. Further graphene is impermeable to gas and liquid. This offers e.g. the advantage that impurities can not pass the present graphene layer and that chemical can be stored/maintained much longer without degradation. Also the layer 35 has a relatively low friction. Thus, e.g. a device, a chamber, a reservoir, a fluid channel, a chip implant are biocompatible for use in an animal or human body. Further a for water and gas impermeable device or layer can be made, e.g. for medicine, such as a container. It is at present possible to form a conformal, flexible, shape 40 changeable, graphene surface. The surface can also be functionalized 12 or passivated, e.g. to switch between a hydrophobic and hydrophilic surface status, to allow gas and water to be selectively permeable, etc.

EXAMPLES

5 The invention is further detailed by the accompanying figures and examples, which are exemplary and explanatory of nature' and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope 10 of protection, defined by the present claims.

BRIEF DESCRIPTION OF FIGURES

Figure 1 shows schematically details of a set-up of a CVD-chamber.

Figure 2a,b show SEM and EDS-images of the present graphene 15 nucleation seed.

Figure 3 shows details of the present transfer method and AFM results.

Figure 4 shows a SEM and TEM-image of a present bilayer graphene and multilayer graphene.

20 Figure 5 shows SEAD image of amorphous silicon nitride before and after graphene heating.

EXPERIMENTAL

The present inventors have developed a homemade socket for copper polishing, and set a standard procedure to clean the 25 copper substrate, which is compatible with state of the arts semiconductor industry. The homemade quartz tube furnace has a fast cooling and heating design (200 °C/ min). A transfer and storage technique is developed in order to keep graphene for long time use.

30 For copper electro-chemical polishing, the copper surface used as catalyst is exposed to an acid solution, whereas all the other sides are fully protected by a socket. Another piece of polished copper is used as reference electrode. The distance of two pieces of copper are self- aligned in order to make constant 35 polishing rate. We finally achieve extremely smooth copper surface. After polishing, the standard cleaning procedures are introduced followed by ACETONE and IPA or Ethanol.

For graphene growth, the to be used copper surface is enclosed inside of copper, which will protect the volatile 40 contamination during synthesis over 1000 C. The nucleation 13 density is enormously decreased with the present methods. Also no contamination is generated. Fast cooling of the furnace also improves the quality of graphene. Thereby one can avoid a necessity of graphene etching by e.g. hydrogen gas. The 5 temperature, methane and hydrogen flow rate (partial pressure) can be adjusted to control the size and the shape of graphene. After growth, the graphene is transferred to an in principle arbitrary substrate, such as thermal oxidized silicon wafer, quartz/glass substrate, silicon nitride substrate, and TEM metal/ 10 carbon grid.

The graphene produced is further store under vacuum or nitrogen gas filled conditions in order to protect graphene from oxidation thereof.

DETAILED DESCRIPTION OF THE DRAWINGS / FIGURES 15 In figure 1 a generic set-up of a CVD-chamber (10) is given. Therein a quartz, alumina, silicon carbide or the like chamber (20) is provided. The chamber has a gas inlet (40), typically provided with a primary pump, a turbo pump, a valve and a pressure gauge. Also a cooling system (not shown) is provided 20 to avoid the overheating of the clamping part of the chamber.

Further an O-ring (60) is provided for isolation of the chamber from the environment. In the chamber a stage (53) for growing graphene is present, the stage being surrounded largely or fully by a metal container (50). The metal container may be of the same 25 material as the catalyst layer used. The container prevents solid particles from entering, and subsequent deposition on the graphene, and allows gaseous species to enter in order to form graphene. A furnace (30) with one or more heating elements substantially surrounding the chamber is provided. The 30 temperature of the furnace may have a maximum temperature above the required temperature in the chamber, such as from 1200 - 1600 °C. The furnace is supported or suspended around the CVD chamber (70). Typically a lubricant such as mica, boron nitride, graphite and the like is provided for easier movement.

35 Heating elements can be made of Nickel-chrome(NiCr), platinum, molybdenum disilicide, tungsten, molybdenum and silicon carbide, and alloys thereof. A heating source may be also be an infrared source, and a lamp. A typical tube size is from 2,5 cm to 30 cm. The tube may be closed on one side, and it may also be open 40 on two sides. The metal chamber may be fully closed, however in view 14 of the present method not vacuum tight, an may also be partially open.

In figure 2 an SEM and Energy-dispersive X-ray spectroscopy (EDS)image of graphene nucleation is presented. A goal of the metal 5 chamber is creating a good environment for a CVD process in order to reduce an impurity level. Impurities may relate to Si02 and volatile particles from the quartz tube environment during heating. Such is considered quite an important issue, since inventors confirmed that the Si02 particle and impurities are the most important nucleation 10 seed. Such is evidence by the present figure.

In figure 3a schematical details of the present process are shown. On a heater (310) a substrate layer (300) is provided. At least one layer of graphene (330) is provided on a support (320) having a transparent window or hole (321) therein. For observation a 15 scanner, microscope, or the like (340) is provided. Optionally a x,y,z and rotation manipulator and a robot are provided. Figure 3b shows details of graphene'film (330) on the release layer (331) suspended on the support (320) or support frame (332). Adhesive layer (331) is applied at the edge of the release layer and the 20 support window for joining them together and damping the vibration. The adhesive layer dimension is from 1 mm to 5000 mm, preferably from 1 mm to 500 mm, more preferably from 1 mm to 100 mm. Figure 3c show shows an AFM-images of the present extremely clean graphene on the present metal substrate by the present growth method, whereas 25 figure 3d shows an AFM-images of the present graphene on boron nitride by the present transfer method. The graphene is atomically flat with a surface (amplitude) roughness as small as ~130 pm.

Figure 4a shows a SEM image of the present graphene and figure 4b a TEM SEAD image, which shows single crystal growth of each 30 graphene layers. The single crystal sizes are from 1 pm to 50000 pm, preferably from 1 pm to 1000 pm. Figure 4c shows a SEM-image of a present bilayer graphene and figure 4d of a present multilayer graphene, the top layer sizes are from 1 pm to 1000 pm, preferably from 1 pm to 500 pm. Figure 4e shows a TEM image of a present 35 multilayer crystallized graphene, which shows Moiré patterns with periodicity ~30 nm (red scale bar 50 nm). Figure 4f shows atomic resolution of 5 nm gold particles on graphene TEM grid, which shows atomic resolution. Graphene is transparent under electron microscope .

40 Figure 5a shows a SEAD image of amorphous silicon nitride with 15 present graphene microheater. Figure 5b shows SEAD image of silicon nitride crystallized by Graphene heating up to 2273 °C (2000 °K). In theory, the heater can reach up to 4273 °C (4000 °K) .

Claims

A method for synthesizing at least one large layer of graphene, comprising the steps of: a) providing a support, the support comprising a first catalytic metal surface, and a carbon source, a hydrogen source, and an inert carrier gas, b ) reducing a surface roughness and / or impurity content of the support surface, c1) introducing the catalytic surface, into a conditioned environment, and c2) introducing the carbon source into the conditioned environment at a pressure of less than 1000 Torr and a flow rate of less than 500 sccm, d) decomposing the carbon source into at least carbon, and e) synthesizing graphene from carbon by activation with the catalyst for a predetermined time to form at least one conformal layer of graphene on the catalytic surface.

Method according to claim 1, wherein the carrier is a container, preferably a single metal container, the container protecting the catalytic surface against environmental influences, such as contaminants and particles, the catalytic surface being accessible to the carbon source and hydrogen source and / or wherein the catalyst comprising surface is one or more of nickel, copper, cobalt, iron, palladium, platinum and alloys thereof, preferably Cu and / or wherein the catalyst surface is of 0.1 μπι-0.5 mm thick, and / or wherein the carrier comprises domains of a second material, such as BN, quartz, mica, and combinations thereof, wherein the domains are preferably selected from flake, a crystalline, film, and combinations thereof.

Method according to claim 1 or 2, wherein the carbon source comprises pure C12 or comprises pure C13 and / or wherein the carbon source is selected from benzene, methane, ethane, ethylene, propane and combinations thereof, and / or wherein the carrier gas is an inert gas, such as a noble gas, such as He, Ne, Ar, Kr, preferably Ar, and / or wherein the hydrogen source is H2.

4. A method according to any one of the preceding claims, wherein in step b) the surface is treated with a diluted carboxylic acid, wherein the carboxylic acid is free from elements other than C, H and O, such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, oxalic acid and benzoic acid and / or wherein a pH is from 1.5-6, preferably from 2-5, more preferably from 2.5-3, and / or where a temperature is raised, preferably to a temperature of 50- 150 ° C, more preferably to a temperature of 60-90 ° C, such as from 70 to 80 ° C, and / or wherein the surface is treated for a time period of 5 minutes to 4 hours, preferably 10 minutes -15 1 hour , such as from 15 to 30 minutes, and / or wherein a solvent is water or an alcohol free of elements other than C, H and O, such as methanol and ethanol, and / or wherein the surface is annealed at a temperature of (Tsmeit). 200) ° C - (Tsmeit-1) ° C, preferably (Tsmeit-70) ° C - (Tsme: Lt-5) 20 ° C, more preferably (Tsmeit_50) ° C - (Ts meit-10) ° C, for example from (Tsmeit-20) ° C - (Tsmeit-15) ° C, and / or wherein the surface is annealed for a period of 5 minutes to 4 hours, preferably 10 minutes - 2 hours , such as from 15 minutes to 60 minutes.

A method according to any one of the preceding claims, wherein the conditioned space is a vacuum chamber, such as a quartz chamber and stainless steel chamber and / or wherein the pressure within the chamber is from 10 ~ 10 - 10 + 3 Torr, preferably from 10 ~ 5 - 10 ~ 2 Torr, and / or wherein the flow rate of the carbon source is from 0.01-500 sccm, preferably from 0.02-300 sccm, more preferably from 0.1-50 sccm, even more preferably from 0.5 -20 sccm, such as from 1-10 sccm, and / or wherein a hydrogen flow rate is from 0.5-1500 sccm, preferably from 1 to 500 sccm, more preferably from 2 to 100 sccm, even more preferably from 5 to 35 sccm , for example from 10-20 sccm.

A method according to any one of the preceding claims, wherein the decomposition and synthesis is carried out for a time period of 1 minute to 24 hours, preferably 5 minutes - 12 hours, more preferably 10 minutes - 4 hours, such as 15 minutes - 2 hours and / or wherein the decomposition occurs by raising the temperature in the conditioned environment, preferably to 400-1600 ° C, more preferably to 600-1200 ° C, such as to 900-1080 ° C, and / or wherein the synthesis of graphene takes place during Decomposition and / or wherein a heating rate is from 10 ° C - 200 ° C / min., And / or wherein a cooling rate is from 10 ° C - 200 ° C / min.

7. Method as claimed in any of the foregoing claims, wherein after step e) f) the one or more conforming layers of graphene are transferred to a release layer, such as by applying a release layer on the one or more conforming graphene layers and / or g) the removing one or more sacrificial layer, such as by a chemical etching process, surface comprising the catalyst, such as by a chemical etching process, such as by a solution of (NH 4) 2 S 2 O 8 and FeCl 3.

8. Method according to claim 7, wherein the release layer is applied as a liquid and is allowed to solidify, preferably by spin coating and / or by evaporation of a solvent, and / or wherein the release layer comprises one or more of an organic silicon compound, such as CH3 [Si (CH3) 20] nSI (CH3) 3 (PDMS), a polymer such as PMMA, polyimide, polyamide, polycarbonate, a resin, such as as (meth) acrylate resin, such as polymers or copolymers of methyl (meth) acrylate or other acrylic monomers, and epoxy, and a natural or artificial rubber, and / or wherein the release layer has a Tgias of 25-200 ° C, more preferably 30-120 ° C, even more preferably from 40-90 ° C, such as 40 to 60 ° C, and / or wherein a frame is provided on the release layer for supporting transfer thereof, and / or wherein the release layer and at least one graphene layer are transferred to a receiving surface comprising one or more of Si, SiO 2, Si 3 N 4, BN, mica, quartz, glass, polymer, rubber and / or wherein the transfer further comprises alignment of the at least one graphene layer and receiving surface, such as by one or more of a target mark on the receiving surface, an optical microscope, a means for rotating the receiving surface, a means for planar movement of the receiving surface, and a means for tilting the receiving surface, and / or wherein the release layer is heated to a temperature above its Tgias, such as 5 -80 ° C above Tgias for a period of 5 minutes - 200 hours, such as 10 minutes - 50 hours under reduced pressure, such as at a pressure of 1CT10 - 10 + 3 Torr, preferably from 10 8 8 5 10 Tor Torr.

9. At least one large layer of graphene, wherein the at least one graphene layer is available with a method according to any one of claims 1-8, and wherein the graphene consists of pure C12 or pure C13 and / or 10, wherein the at least one layer has a has a defect density of less than 1CT1 defects / cm2, preferably less than 1CT3 defects / cm2, more preferably less than 5 * 1CT4 defects / cm2, even more preferably less than 1CT4 defects / cm2, where particle sizes are 50 run diameter and larger, and / or wherein the at least one graphene layer is at least 99.5% pure, preferably at least 99.9% pure, and in the case of C12 is preferably at least 99.99% pure, such as 99.999% pure.

10. Including at least one large layer of graphene according to claim 9 or obtainable by a method according to any one of claims 1-8, such as one or more of a microfluidic device, an implant, a semiconductor device, quantum spintronics, a transistor, a resistor, a coil, a diode, a conductive member, a chip, a TEM carrier membrane, a particle or gas filter membrane, a biochemical sensor, a micro- or nano-electromechanical system device, an optical coating and an anti-oxidation coating.

11. At least one large layer of graphene according to claim 9 or obtainable according to a method according to any of claims 1-8, on an optionally perforated membrane, such as silicon nitride, silicon, hexagonal boron nitride film, and SiO 2 membrane, optionally with at least one contact electrode, preferably an Au, a Cr, Pt, a W, a Pd, and a Mo electrode, the electrode preferably being capable of one or more of TEM imaging, chemical detection, biosensing, infrared or microwave laser mode lock application, flow cell and fluid cell application, such as a micro or nano fluid cell and biochemical fluid cell, and anti-oxidation application and / or wherein the graphene is a patterned graphene resistance wire, such as one or more for micro or nanoheating, and 40 voltage detection in a pressure sensor application and / or where graphene is on or between a hexagonal boron nitride film for use in one or more of a transistor, a spintronics a pn junction, a photos flow detector, and a super computer application.