Graphene-metal composite

Abstract

A graphene-metal composite comprising at least two graphene layers and at least one metal layer in between the two graphene layers. The metal layer)s) are essentially free of residuals (e.g., water, organic solvents, metal oxides, metal halides, halides, halogen molecules, and organo-metallic compounds), have a layer normalized spatial thickness deviation lower than 10%, cover at least 90% of an adjacent one of the at least two graphene layers and / or at least one of the graphene layers defect density is lower than 1e11 defects per cm2.

Description

[0001] 14804-PC

[0002] GRAPHENE-METAL COMPOSITE

[0003] TECHNICAL FIELD

[0004] The present invention relates to graphene metal composite and a method of manufacture thereof by thin atomic-molecular layer deposition. In particular, the invention relates to coating patterned surfaces by a graphene-metal composite and in particular to devices containing the graphene metal composite.

[0005] BACKGROUND ART

[0006] The systematic miniaturization of integrated digital electric circuits elements was and is the main driving force of very large system integration (VLSI) in semiconductor devices leading to higher circuit element density and lower power consumption. On the other hand, as result of scaling down interconnection metal lines have lower conductivity, and relatively increased energy consumption. Typically designed as a multilayered net, high resolution interconnects are formed by repeated steps which include deposition in etched trenches and vias which connect between layers. Thus, there is a need for accurate deposition processes that will enable high quality deposition of interconnect lines of ultra-high conductivity at fine resolution and at pattern high aspect ratio. High aspect ratio is also related to by a high ratio between the depth of a specific feature and in lateral dimension ("width").

[0007] Recently, the emergence of new electronic materials such as graphene or graphene metal composite has shown potential for use as ultra-high conductive and as on surfaces and as a potentially highly reliable composite material. However, crucial obstacles still prevent industrial application of graphene-metal composite as a new type of interconnect, mainly in the step of in situ graphene synthesis and metal - graphene interlayer formation and non-satisfactory properties of the product.

[0008] Advanced coating has played a significant role in advancing material technologies in the last decades, whether it is in the development of harder coating or 14804-PC low friction coating, optical coating or electrically conducting coatings. The development has been in many cases advanced by the development of new materials, new methods of coating and more complex arrangements of layer structures to achieve a device purpose. Coating has advanced to achieve functional targets by improving physical properties, e.g., forming an advanced layer structure arrangement to provide high electrical conductivity, or by enabling intricate device manufacturing, e.g., miniaturization of integrated circuit elements.

[0009] There is a need for better thin layer coating techniques of surfaces by graphene and metal, for forming better composite materials that may provide better conductivity. There is also a need for better coating techniques for forming graphenemetal composite coatings, providing better chemical or mechanical properties and / or better optical properties.

[0010] Alternative non-limiting examples of areas in which advanced coating with carbon allotropes and, in particular, with graphene are desired, include the use of graphene coating as permeation barrier, a lubricant, light collector, transparent electrode and more. Specifically, advanced coating techniques are desired to produce graphenemetal composites. Graphene metal composites have potential for providing synergistic properties such as ultra-high electric conductivity or ultra-high heat conductivity which may exceed the conductivity properties of metal conductors. However, currently available methods for producing graphene metal composites provide products that are shy of ripping the full potential of these promising products and suffer from many limitations. There is therefore still an unmet need for finely tailored and improved graphene metal composites.

[0011] SUMMARY OF INVENTION

[0012] TECHNICAL PROBLEM

[0013] The aim of the invention is to provide a graphene-metal composite e.g., as a coating or a graphene-metal composite patterned coating on a surface or as an independent product. The aim of the invention according to certain aspects is to provide a method for forming a graphene-metal composite coating on a surface by thin 14804-PC layer deposition of molecular precursors and their transformation (polymerization) to form a graphene coating, and by thin layer deposition of metal to form inter layers of the graphene-metal composite. According to a further aim of the invention exfoliation can for example be used to form an independent graphene-metal composite.

[0014] The present invention relates to graphene metal composite and a method of manufacture thereof by atomic-molecular layer deposition or molecular layer deposition. In particular, the invention relates to coating of patterned surfaces by a graphene-metal composite and relates to devices containing the graphene metal composite.

[0015] A further aim of the invention is to provide graphene-metal composites having improved and / or synergistic properties such as ultra-high electric conductivity or ultra- high heat conductivity. Yet, a further aim of the invention is to provide a protective graphene-metal composite coating and to provide a method of producing a graphenemetal composite coating that will keep the surface or substrate intact, further serving as a diffusion barrier and / or providing mechanical protection to the substrate.

[0016] A further aim of the invention is to provide a graphene-metal composite coating to a surface having a minimal number of defects, or essentially no defects of the graphene matrix. Yet a further aim of the invention is to provide a graphene metal composite having uniform metal interlayers.

[0017] Graphene quality and growth temperature are important requirements for efficient forming of graphene-metal composite barriers. As is disclosed hereinbelow, the method according to the invention provides for forming high quality graphenemetal composite at relatively low temperature. It is an aim of the invention to provide a method of coating performed at relatively low effective temperature range and to provide for controlled graphene-metal composite quality and at controlled substrate temperature.

[0018] According to the invention techniques for producing graphene metal composite are provided. Advanced thin layer coating techniques include Chemical Vapor 14804-PC

[0019] Deposition (CVD), Atomic Layer Deposition (ALD) and Molecular Layer Deposition (MLD). Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high quality, and high-performance thin films. In typical CVD, a substrate positioned in a reaction chamber, typically under high or ultra-high vacuum, and is exposed to one or more volatile precursors, which react and / or decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber.

[0020] ALD and MLD are thin-film deposition techniques that, by relying on selfterminating surface chemistry, enable the control of the amount of deposited material down to the atomic or molecular level. See for example: Van Bui, H. et. al., 2017, Chemical Communications 53(1):45-71. Advanced coatings with carbon allotropes and for forming graphene-metal composites are desired in many applications.

[0021] SOLLUTION TO PROBLEM

[0022] According to a first aspect of the invention, a graphene-metal composite is provided, the graphene-metal composite comprises at least two graphene layers and at least one metal layer being disposed between two graphene layers, characterized by at least one of:

[0023] • any one of the metal layers is essentially free of residuals selected from the group consisting of water, organic solvents, metal oxides, metal halides, halides, halogen molecules, and organo-metallic compounds;

[0024] • at least one metal layer having layer normalized spatial thickness deviation lower than 10%;

[0025] • at least one metal layer covering at least 90% of an adjacent one of the at least two graphene layers; and

[0026] • graphene layer defect density lower than lell defects per cm2.

[0027] According to a second aspect of the invention, a graphene-metal composite is provided, the graphene-metal composite comprises graphene layers and at least one metal layer, at least one metal layer being disposed between two graphene layers, wherein the metal layer is in the form of nanoclusters. 14804-PC

[0028] According to a third aspect of the invention, a graphene-metal composite is provided, the graphene-metal composite comprising graphene layers and metal layers, at least one metal layer being disposed between two graphene layers, wherein any one of the metal layers is essentially free of residuals selected from the group consisting of water, organic solvents, metal oxides, metal halides, halides, halogen molecules, and organo-metallic compounds.

[0029] According to a fourth aspect of the invention, a graphene-metal composite is provided, the graphene-metal composite comprising graphene layers and metal layers, at least one metal layer being disposed between two graphene layers, wherein the thickness of the metal layer is larger than 0.34 nm.

[0030] According to a fifth aspect of the invention, a device is provided, the device comprising the graphene metal composite described above.

[0031] According to a sixth aspect of the invention, a method for producing a graphene-metal composite is provided, the methos comprising the steps of: depositing a molecular graphene precursor on a surface; transforming said deposited molecular graphene precursor into a graphene layer; depositing a metal on top of the graphene layer to obtain metal layer deposited on the graphene layer; depositing a molecular graphene precursor on top of the metal layer and transforming the moleculargraphene precursor into a graphene layer on top of the metal layer, to obtain a metal graphene composite.

[0032] ADVANTAGEOUS EFFECTS OF INVENTION

[0033] The accurate thin layer deposition of the invention enables accurate graphene layer formation from precursors and accurate metal deposition for forming graphenemetal composite in applications in which it was not possible before. Forming the graphene-metal composite through such thin layer deposition provides, inter alia, (i) ultra-high electrical conductivity (ii) good thermal and chemical stability; (iii) good thermal conductivity; and (iv) good adhesion or bonding to the target surface, which, 14804-PC in turn, provide also for reliability of the formed composite, and in respective applications provide for improved conductivity of a formed interconnecting element.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] For better understanding of the present invention and in order to exemplify how it may be implemented in practice, several embodiments are hereby described, which should be interpreted only as non-limiting examples, with reference to the accompanying figures. It is noted that the sizes and scale of the embodiments presented in the figures are exemplary and non-limiting.

[0036] It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[0037] Figure 1A depicts a graphene-metal composite according to the invention.

[0038] Figure IB depicts a schematic representation of a graphene-metal composite coated substrate having a surface coated by the graphene-metal composite of the invention.

[0039] Figure 2 depicts a cross-sectional schematic representation of a substrate having a patterned surface coated by the graphene-metal composite of the invention, according to an embodiment of the invention. 14804-PC

[0040] Figure 3 depicts a schematic representation of a product comprising a 3D pattern comprising a conformal coating by a graphene-metal composite according to an embodiment of the invention.

[0041] Figure 4 depicts a schematic representation of a product comprising graphene layers that are bonded by a linker.

[0042] Figure 5 depicts a block diagram representing a general method for forming a graphene interfacial layer or coating on a surface according to an embodiment of the invention.

[0043] DESCRIPTION OF EMBODIMENTS

[0044] Although the invention is illustrated and described herein as embodied in figs. 1 to 4 and examples 1 to 3, the invention is not limited to the details shown because various modifications and structural changes may be made without departing from the invention and the equivalents of the claims. However, the product, the compositions construction and method of production or operation of the invention together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

[0045] Graphene-Metal Composite

[0046] According to a first aspect the present invention provides a graphene-metal composite coating or a graphene-metal composite patterned coating on a surface.

[0047] Reference is made to Figure 1A, schematically illustrating the graphene-metal composite of the invention. The graphene-metal composite 120 is formed of interleaved layers of graphene 124 and metal 122, where in this example the bottom layer of the graphene-metal composite 120 is a graphene layer 124a, while in other examples the bottom layer may be a metal layer. In some embodiments, the invention excludes graphene-metal composites having a graphene layer as a bottom layer. In some embodiments, the invention excludes graphene-metal composites having a metal 14804-PC layer as a bottom layer. Figure IB illustrates a product 100 comprising a substrate 110 having a surface 112, while the surface is coated by the graphene-metal composite 120 of the invention, according to another aspect of the invention. The bonding of the graphene layer to the surface can be any one of (i) weak bonds, e.g., adhesion bonds, (ii) pi bonds and (iii) strong covalent bonds, thus forming a graphene-metal composite coated material. According to some embodiments the graphene-metal composite 120 is a coating on a substrate 110 having a surface 112. According to some embodiments, as depicted in the example illustrated in Figure IB, the surface 112 of the graphenemetal composite coated substrate 110 is covalently or pi-bonded through bonding 125 to the surface 112. According to the schematic illustration the graphene-metal composite comprises four graphene layers and two metal layers. According to some embodiments, the numbers of graphene layers may be at least 3 layers, at least 10 layers, at least 50 layers or at least 500 layers. According to some embodiments, the number of metal layers can be substantially equal to the number of graphene layers, less than 90% of the number of graphene layers, less than 50% of the number of graphene layers or less than 20% of the number of graphene layers.

[0048] Patterned Surface

[0049] According to some embodiments of the invention, the product is a graphenemetal composite coated on the surface of a substrate that is a patterned surface. Figure 2 schematically illustrates the invention according to such embodiments. In Figure 2 a cross-section through patterned substrate 150 is schematically illustrated, whereas the patterned surface comprises trenches 152 and vias 154 and the graphene-metal composite coating is indicated by lines 158. According to some embodiments, the patterned surface may be formed on the substrate by different methods e.g., by additive methods such as 3D printing, inkjet printing or screen printing or by subtractive methods such as engraving or etching. According to some embodiments, the surface of the substrate is treated by masking or coating to form the graphene-metal composite only on part of the surface. According to some embodiments, the substrate is a metal, e.g., an interconnect interlay of a printed circuit or a non-metal, e.g., a semiconductor material substrate for a VLSI electronics chip patterned by lithography. According to 14804-PC respective embodiments, the patterned surface is a surface of a lithographically etched substrate. According to some embodiments, the patterned surface is characterized by geometrical features having a profile with at least some of the dimensions smaller than 500 nm, smaller than 100 nm, smaller than 50 nm or smaller than 20 nm.

[0050] Uniformity

[0051] The term "graphene" refers an allotrope of carbon consisting of a single layer in which carbon atoms are generally connected by sp2bonds and forming a 'honeycomb' arrangement. The graphene may be contaminated, e.g., with heteroatoms such as Si, Ge or Sn. Hydrogen atoms may be covalently bonded to the peripheral carbon atoms forming the single layer or alternatively be replaced by functional groups which in turn may covalently connect the graphene layer to adjacent surfaces. These functional groups and contaminations together with other defects may in general form a small percentage of defects in the graphene idealized structure and aromatic character without significantly changing its ability to form graphene-metal composite having specific synergistic properties such as ultra-high electrical conductivity or ultra- high heat conductivity, or other properties such as an ability to form a diffusion barrier.

[0052] The term "defects" as used herein means a disruption in the normal structure the graphene lattice and includes disruption of the ideal extended pi-bonded network. This includes an absence of a carbon atom in the graphenic lattice, presence of sp3bound carbons in the graphene network instead of sp2bound carbon atoms, which may be caused by breaking of a C-C bond, the change of conjugation of a C-C bond, intentional introduction of functional groups and / or any other changed hybridization state of a carbon atom (from sp2to sp3hybridization). Defects also include any other form of disruption of the ideal extended pi-bonded network such as disposition, e.g., the formation of localized heptagon-pentagon carbon bond formation or interstation, e.g., the replacement of a carbon atom with a nitrogen atom in the graphene lattice. The singular form "defect" refers to such a change occurring in one location of the graphene lattice. One of the aspects by which the quality of a graphene coating is quantified by a "defect density", i.e., by the number of defects per cm2. 14804-PC

[0053] The term "uniformity" refers to the uniformity of a film or a coating having substantially equal thickness and composition (and other properties) at each position along a planar substrate, e.g., along a 5 mm chip or 300mm wafer, wherein the uniformity of each uniform property may respectively be defined by a range or variance or any other statistical descriptor of the property, thus for example composition or defect uniformity may be characterized by the maximum variation in composition or defect number (per area) respectively. Thus, for example, uniformity in the number of layers may be defined by having a variance in the number of layers by not more than 20 layers, not more than 10 layers, or not more than 4 layers over the relevant tested region. Additionally, or alternatively, uniformity may be characterized by a normalized spatial thickness deviation (e.g., the statistical deviation in percent from the mean or median). Uniformity measures may be applied to simple regions (e.g., a region bound by a simple polygonal) or on to complex regions e.g., uniformity of thickness of the graphene-metal composite over an interconnect mesh which clearly is a complex region or surface.

[0054] According to some embodiments at least one metal layer covering at least 90% of an adjacent one of the at least two graphene layers. According to some embodiments, the graphene-metal composite coating of the surface is uniform, whereas uniformity is characterized by uniformity of the number of graphene layers forming the coating of a coated region, wherein the difference between the maximal number of graphene layers in a first location of the coated region and the minimal number of graphene layers in a second location of the coated region is less than 10 layers, 6 layers or 4 layers.

[0055] According to some embodiments the graphene-metal composite coating is conformal to the surface i.e. , the graphene-metal composite exhibits conformality over a respective region.

[0056] The term "Conformality" refers to properties of a coating of a 3D pattern e.g., having substantially the same thickness and composition, (and / or other physical properties) throughout the three-dimensional conformation (or feature) of interest. 14804-PC

[0057] Thus, for example, a thickness conformal coating of a pattern having 3D features such as trenches, protrusions or vias will have the substantially the same thickness along any location of the pattern. To assess the conformality of a coating of a three-dimensional pattern it is possible to characterize the geometry of the three-dimensional pattern and to provide a conformality measure consistent with the characterized geometry. Three dimensional patterns such as a circular hole, a square hole or a trench may be characterized by a two-dimensional descriptor such as the aspect ratio, i.e., depth to width ratio. This type of descriptor may be sufficient for a circular hole but in some cases may be insufficient for more complex patterns such as elongated holes, trenches, or elongated pillars. A Generalized Aspect Ratio (GAR) may be calculated as GAR = L-p / 4A, wherein L is the features depth (or height for a protrusion), p is its perimeter at the top and A is its area at the top (or bottom respectively). For a circular via example this reduces to L / w, where w is the width (radius) of the via. Other quality characterization approaches are, for example, reviewed by Cremers et. al., Appl. Phys. Rev. 6, 021302 (2019).

[0058] If for example, a thickness profile of the graphene-metal composite is experimentally obtained, then it is possible to determine the depth, for a recess, or the height, for a protrusion, at which the coating thickness (by the graphene-metal composite) equals 50% of the coating thickness at the top (or the bottom for a protrusion). This 'penetration' depth may be designated as PD50. Alternatively, any proportional thickness ratio, e.g., the depth at which the coating thickness is 80% of the top (or bottom respectively), designated PD80, may be used to measure the aspect ratio or GAR of the measured pattern coating, with depth L, as defined above, being the measured penetration depth. Thus, a circular hole having PD50 that is 20 times the radius of the circular top will have GAR-PD50 of 10.

[0059] Referring to Figure 3 characterization of the conformality of the coating by the graphene-metal composite in a product is illustrated by a schematic section 200 through a coated layer in a region comprising one 3D pattern, e.g., a section through a circular hole 204, having a slightly conic cross section. The circular hole is coated by coating 208 which, according to the schematic example, is getting thinner inside the 14804-PC circular hole. The diameter d of the circular hole, at the top, after coating is marked 212, the depth PD50 is denoted by distance 216 and the GAR-PD50 is PD50 / d which is approximately 5. According to some embodiments the product comprises coated patterns characterized by GAR-PD50 that is larger than 3, larger than 5, larger than 10 or larger than 30. Alternatively, the quality of the coating can be described by the normalized depth in which the coating reached a certain coating ratio, thus for example the normalized half-thickness penetration depth (normalized PD50) is the ratio of the depth 216 to the full depth of the circular hole 220. According to some embodiments, this ratio for 3D coated features on the surface of the material according to the method of the invention is higher than 0.5, or higher than 0.7. According to some embodiments the ratio PD80 to the full depth is higher than 0.4, or higher than 0.6.

[0060] Number of Layers and Sequence

[0061] According to some embodiments, the product of the invention comprises the graphene-metal composite coated surface comprising at least two layers of graphene and at least one metal layer interlayered in between said graphene layers. According to some embodiments, a metal layer comprises at least one metal and may comprise one or more non-metal elements. According to some embodiments the product of the invention comprises between 2-6 layers of graphene, in some embodiments 5 to 12 layers of graphene. According to some embodiments the product of the invention comprises more than 10 layers of graphene. According to some embodiments the product of the invention comprises less than 50 or less than 100 layers of graphene. According to some embodiments, the thickness of the graphene-metal composite may be up to 50 nm or up to 100 nm. According to some embodiments the graphene layers and metal layers are interlayered, having several separate layers of metal set between layers of graphene (which, as noted above, may also be comprised of several monoatom thick graphene layers). Each metal layer can be n atoms thick, wherein n is between 1 and 20. Thus, according to some embodiments the total thickness of the graphene-metal composite. According to some embodiments the graphene-metal composite comprises at least one metal layer wherein the thickness of the at least one metal layer is monoatomic. The metal layer may also be thicker that monoatomic and 14804-PC may also exceed the distance between adjacent layers of graphite being 0.34 nm. Thus, the thickness of the metal layer may be higher than 0.34 nm, higher than 0.37 nm, higher than 0.40 nm, higher than 0.45 nm or higher than 0.50 nm.

[0062] According to some embodiments the composite material comprises a first metal layer comprising one or more metals and a second, different, metal layer comprising one or more metals. According to some embodiments the graphene-metal composite comprises a first metal layer of a first metal and a second metal layer of a second metal forming a heterogeneous metal layer (having different regions in the layer with different compositions) or an alloy (having a substantially fixed composition). According to some embodiments the graphene-metal composite comprises a metal layer of the first metal and a metal layer of the second metal that are disposed between the same two graphene layers. According to some embodiments the graphene-metal composite comprises a heterogeneous metal layer having a mole ratio between at least two different metals which differ from their relative electric potential or relative atom size.

[0063] More About Bonding Between Graphene Layers

[0064] According to some embodiments the product of the invention further comprises the graphene-metal composite material comprising a bond between two adjacent graphene layers. According to some embodiments, the bond between the graphene-metal composite and the surface of the material is selected from a covalent bond ionic bond and a pi interaction as known in the art (e.g., between an electronegative functional group such as an alkyl halide and an aryl derivatized by an electron withdrawing group). Referring to Figure 4, schematically illustrating a part of a graphene-metal composite comprising three graphene layers, 302, 304, 306, of which two graphene layers 304 and 306 are bonded by linkers 312 and comprising metal layers 303 and 305 in between the graphene layers. The graphene linkers 312 may be different from linkers 315 which may link the graphene-metal composite to a substrate. According to some embodiments, the local defects formed by the linkers are in low concentration, i.e., low number of defects per cm2. According to such embodiments, 14804-PC the bonding provides robustness and mechanical strength to the graphene-metal composite without compromising designed properties such as ultra-high electric conductivity or ultra-high heat conductivity. According to some embodiments of the invention a device comprises the graphene-metal composite product.

[0065] ALD

[0066] According to a general aspect of the invention, ALD and MLD techniques are used to form the graphene-metal composite on top of the surface or patterned surface.

[0067] ALD and MLD are deposition techniques based on the sequential use of a gasphase chemical process are pulsed or sequenced methods of deposition, collectively referred to as ALD, wherein each sequential step is also referred to as a cycle. ALD is a subclass of chemical vapor deposition. Typically, ALD uses (molecular) precursors (also called "reactants"). These precursors are deposited on the surface of a material / substrate and potentially react with the surface of the material, one at a time in a sequential, self-limiting manner, to form chemical bonds with the surface of the material. The chemical bonds may be weak bonds e.g., adhesion bonds or strong bonds such as covalent bonds. Typically, a cycle begins with a pulsated release of at least one of the precursors from a heated container into a reaction chamber, followed by an incubation ("wait") period in which at least part of the released precursor is deposited on the surface of the material / substrate positioned inside the reaction chamber, wherein in some cases the released precursor reacts with other deposited chemical moieties on the surface of the substrate or with the surface of the substrate.

[0068] Method

[0069] Referring to Figure 5, a general method for forming a graphene-metal composite coating on a surface according to an aspect of the invention is disclosed. According to embodiments of the invention the method comprises obtaining a graphene molecular precursor comprising at least one Ce-Cioo hydrocarbon (step 420). In some embodiments, the graphene molecular precursor is added to a solvent or liquid carrier to form a solution or a suspension respectively. In some embodiments the 14804-PC molecular precursor is used in a solid state (e.g., a powder), without a liquid carrier or solvent, which is sublimed during the deposition step.

[0070] The term "molecular precursor" refers to a compound that participates in a chemical reaction that produces another compound. Specifically, the term "graphene molecular precursor" refers to a compound or a mixture of compounds that after reaction, their main carbohydrate backbone becomes part of a graphene coating, film or layer. According to certain embodiments, the graphene molecular precursor mixture comprises a mixture of Ce-Cioo hydrocarbons. According to some embodiments, the graphene molecular precursor comprises at least one Ce-Cioo hydrocarbons functionalized by a group capable of forming a graphene layer (i.e., a "tethering group", for example by halides which undergo Ullmann reaction to yield graphene. According to some embodiments the graphene molecular precursor comprises at least one Ce- Cioo hydrocarbon derivatized by a tethering group capable of bonding by covalent bond to the surface of a material. According to certain embodiments the term graphene molecular precursor does not include Ce-Cioo hydrocarbons functionalized by a tethering group.

[0071] The hydrocarbon of at least one compound is the building block of the graphene to be, is made of an aromatic carbon skeleton which may be small aromatic molecules such as benzene or consisting of several aromatic rings fused to each other (polycyclic aromatic hydrocarbons). The method according to the invention may employ different graphene molecular precursors having different shapes, in attempt to provide high graphene coverage with a minimal number of defects in the graphene coating. After their deposition on the surface these building blocks will, later on, form during a transformation step, e.g., by radiation or by maintaining elevated temperature in the reaction chamber, carbon-carbon bonds between them to generate the graphene network.

[0072] Precursors

[0073] According to some embodiments, the graphene molecular precursor comprises at least one compound selected from the group consisting of: 14804-PC compound A having molecular formula I: G1-X1iY1mY2n, and compound B having molecular formula II: G1-X1iX2jY1mY2n, and compound C having formula III: G-Y1mY2n; wherein, G1is a Ce-Cioo hydrocarbon component, X1is a first tethering group, X2is a second tethering group, Y1is bromine, chlorine or iodine, Y2are selected from the group consisting of hydrogen, halogen radical and -COOH and i, j, m and n are independent integer numbers having a value selected between 1 and 20.

[0074] According to some examples the compound is a Ce-Cioo polycyclic aromatic hydrocarbon (PAH), optionally comprising heteroatoms selected from silicon, germanium, zinc, sulfur, nitrogen and oxygen. In some embodiments the at least one compound is selected from the group consisting of rubrene, coronene, p- hexabenzocoronene, hexa-cata-hexabenzocoronene, pentacene, hexaphenylbenzene, perylene, chrysene, pyrene, PAHs of compounds I - V or combinations thereof.

[0075] 14804-PC

[0076] According to some embodiments, the graphene molecular precursor is mixed with a solvent. According to some embodiments the mixture is a solution or a colloid. According to some embodiments the colloid mixture may be a homogeneous mixture or a non-homogeneous mixture. According to some embodiments the solvent can be selected from any solvent which is known in the art to solubilize polycyclic aromatic hydrocarbons (PAHS), or derivatized PAHs such as halogenated PAHs. By way of example, the solvent can be selected from acetone, methylethyl ketone, diethylether, tetrahydrofurane (THF), hexane, heptane, toluene, benzene, phenyl, xylene (ortho, 14804-PC meta, para or mixture thereof, i.e. xylenes), dibromomethane, dichloromethane, dibromobenzene, or dichloromobenzene or mixtures thtereof. According to some embodiments, the reservoir is separated from the reaction chamber by a valve. According to some embodiments a manifold connects the reservoir to the reaction chamber. According to some embodiments, the conditions in the reservoir (e.g., temperature and pressure) are different from the conditions in the reaction chamber. According to some embodiments the conditions in the manifold are different from the conditions in the reservoir or the reaction chamber, e.g., the temperature of the manifold may be different from the temperature in the reservoir or the reaction chamber.

[0077] According to some embodiments the molecular precursor is a solid e.g., in powder form. According to some embodiments the solid is a mixture. According to some embodiments the solid is heated to enable injecting the molecular precursor into the reaction chamber.

[0078] According to embodiments, the at least one graphene molecular precursor comprises a Ce-Cioo hydrocarbon being derivatized by at least one tethering group. The term "tethering group" refers in the context of the invention to a functional group which is capable of forming a bond (e.g., covalent bond) by means of a chemical reaction with molecular entities being part of the surface. The formation of the covalent bond results in the covalent bonding between the molecule which comprises the tethering group (e.g., the graphene molecular precursor) and the surface (e.g., the metallic or non-metallic surface).

[0079] It is noted that in some embodiments, the method excludes the use of graphene molecular precursors having tethering groups to the surface. In general, it is noted that whethertethered or untethered, the selection of graphene molecular precursor for the forming of the first graphene layer depends on the type of the surface onto which the graphene molecular precursor is being deposited.

[0080] According to some embodiments the at least one tethering group is selected from of -I COOR2, -R^ChR2, -i PChHz, -R^OH, -NR3R4and -R1SH wherein R1is selected 14804-PC from a bond, Ci-s saturated or unsaturated, substituted or unsubstituted alkyl; R2is H or Ci-8 saturated or unsaturated, substituted or unsubstituted alkyl, R3and R4are independently selected from H, Ci-s saturated or unsaturated optionally derivatized alkyl or combinations thereof. When the metal to be coated is titanium then X1may further be selected from -R1SiOH and R1SiCl3.

[0081] According to some embodiments, the at least one tethering group is selected from the group consisting of Ce-Czo aryl unsubstituted or substituted by an electron withdrawing group, Ce-Czo substituted or unsubstituted heteroaryl, -R1SiOH, R1SiCl3, - R4X , -NR3R4, -R1COOH, -R^ChR2, and -R^ChHz, or combinations thereof wherein R1is selected from a bond, Ci-s saturated or unsaturated, substituted or unsubstituted alkyl, X is selected from -OH, -Cl, -Br, -F, or -I, R3and R4are independently selected from H, Ci-s saturated or unsaturated optionally derivatized alkyl.

[0082] According to some embodiments, the electron withdrawing group is selected from the group consisting of a halide, -CN, -NO2, -CHO, -COOR2, -C(=O)R5wherein R2is H or C1-8 saturated or unsaturated, substituted or unsubstituted alkyl R5is Ci-s saturated or unsaturated, substituted or unsubstituted alkyl.

[0083] According to some embodiments the at least one tethering group is selected from the group consisting of Ci-s siloxyl, -R^ChR2, -R^ChHz, -SiR1R2R3, - NR4R5, -R5COOR6and R7SH wherein R1, R2, and R3are independently selected from H, - OH, -Cl, -Br, -F, -I , C1-8 saturated or unsaturated optionally derivatized alkyl, and at least one of R1, R2, and R3is -Cl, -Br, -F or -I ; R4and R5are independently selected from H, C1-8 saturated or unsaturated optionally derivatized alkyl; R6is H or Ci-s saturated or unsaturated optionally derivatized alkyl; R7is a bond or Ci-s saturated or unsaturated optionally derivatized alkyl.

[0084] Thus, according to some examples the molecular precursor is at least partially reacted with the surface to form covalent bonds between them to obtain a surface covalently linked to a graphene molecular precursor layer. For example, when the tethering group is mercaptomethylene then sulfur-metal bonds spontaneously form between the graphene molecular precursor and the metallic surface. 14804-PC

[0085] Turning back to Figure 5 obtaining the graphene molecular precursor in a reservoir (step 420) is followed by injecting the graphene molecular precursor mixture from the reservoir into the reaction chamber (step 425). According to some embodiments, performing injection of the graphene molecular precursor mixture is carried out by at least one of:

[0086] (1) generating a pressure difference between the pressure in the reservoir and reaction chamber and releasing the graphene molecular precursor mixture into the reaction chamber;

[0087] (2) carrying the graphene molecular precursor mixture by a carrier gas flowing in the direction according to a pressure gradient; and

[0088] (3) atomizing the graphene molecular precursor mixture, i.e., generating droplets of the mixture, and releasing the generated droplets in direction into the reaction chamber (according to the pressure gradient).

[0089] According to some embodiments, injecting the graphene molecular precursor mixture is performed by directing the graphene molecular precursor mixture through the manifold connecting the reservoir to the reaction chamber. According to some embodiments injecting the graphene molecular precursor mixture is performed by pulsed injection. According to some embodiments injecting the graphene molecular precursor mixture is performed by continuous injection.

[0090] Generally, the graphene molecular precursor is deposited by vacuum deposition. The term "vacuum deposition" relates to a family of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes typically operate at pressures well below atmospheric pressure (i.e., vacuum).

[0091] According to some embodiments, the injection of the graphene molecular precursor mixture into reaction chamber is promoted by at least one process that kinematically couples the carrying of a volatile solvent with carrying the low volatility 14804-PC graphene molecular precursor(s). Thus, for example, atomizing of the mixture forms droplets of solvent which comprise the graphene molecular precursor mixture and enables a flow of these droplets into the reaction chamber and thereby, the transfer of the graphene molecular precursor mixture onto the surface of the material that is to be coated. According to some embodiments, the ratio between the pressure in the reservoir and the pressure in the reaction chamber is higher than 100, 500, 1000 or 10,000. According to some embodiments, the pressure in the reservoir is higher than 20, 100, 200 or 500 Torr and the pressure in the reaction chamber is lower than IE-1, IE-2, IE-3 or IE-6 Torr. According to some embodiments, maintaining the pressure difference, e.g., by opening a valve for very short periods, enables carrying low volatility graphene molecular precursors from the reservoir to the reaction chamber, by the solvent that has a relatively high volatility (high partial pressure). According to some embodiment, a gas carrier is bubbled into the reservoir. According to some embodiments, the gas carrier in a non-reactive gas (with respect to coating process) or an inert gas. According to some embodiments, atomizing the graphene molecular precursor mixture may be performed by an ultrasound atomizer or by injecting the graphene molecular precursor mixture through a nozzle.

[0092] According to some embodiments, the temperature of the reservoir, and in particular the temperature of the graphene molecular precursor mixture, which is maintained in the reservoir, is lower than the temperature in which the graphene molecular precursor starts to dissociate or become chemically unstable.

[0093] According to some embodiments, products of the reactions in the reaction chamber and unreacted precursors are evacuated from the reaction chamber. According to some embodiments, the injection of the molecular precursors is performed under self-termination conditions which imply that, to begin with, there are more reaction sites, e.g., sites on the surface to adhere to, than molecular precursors in the reaction chamber, at the vicinity of surface sites of interest. This changes as the process advances until the surface sites saturate. However, the self-terminating conditions contribute to the homogeneity and conformality of the coating process. In addition, the flow characteristics of the injected molecular precursors is controlled to 14804-PC provide for homogeneous and conformal coating. According to some embodiments the pressure in the reaction chambers is sufficiently low when graphene molecular precursors are injected therein to provide a large mean free path of the graphene molecular precursors in the gas phase (average distance the molecular precursors will move between collisions). According to some embodiments, to determine if the pressure is sufficiently low or, equivalently, to determine if the mean free path is sufficiently large the mean free path is compared to the dimensions of the pattern of interest (formulas for estimating the mean free path are well known in the art). This ratio is referred to as the Knudsen number. High Knudsen number reflects that in the vicinity of a surface site at the pattern of interest molecular precursors are less hindered (e.g., by other gas phase moieties) from reacting at the surface site. Thus, for example, if the mean free path of a certain moiety is 5pm and the width of a trench which is targeted for coating is 50 nm then the ratio (AKA Knudsen number) is 100 which in general reflets favorable conditions for such surface related reactions. Thus, according to some embodiments, the Knudsen number corelating the at least one molecular precursor on interest, to the diameter of the patterns of interest, is larger than 30, 300, 1000 or 3000. For example, if the temperature in the reaction chamber is 200°C, and the pressure is 0.05 Torr, the mean free path of the graphene molecular precursors such as hexabromobenzene with molecular collision diameter ranging between 0.4 nm to 0.6 nm can be calculated. The mean free path is calculated by =

[0094] KbT

[0095] , where Kb is Bolzman constant, T is the temperature (°K), d is the molecular 2nd2P diameter (m) and the pressure P is measured in Pascal, and this example is approximately 880 microns. Thus, for features of about 20nm the Knudsen number is around 4400. Such high values imply that the interactions at the vicinity of such features is mainly surface-particle interaction and not particle-particle interaction. At the presence of other chemical moieties such as the solvent (e.g., toluene), now in gas phase, the computation is slightly more complex, but the general result is roughly similar.

[0096] Turning back to Figure 5, according to the illustrated method, the at least one graphene molecular precursor is deposited on top of the surface of a material (step 14804-PC

[0097] 430) by applying thin layer deposition, to obtain a surface at least partially coated with the at least one graphene molecular precursor and transformed into a graphene coating surface (step 440) to obtain a graphene coated surface. According to some embodiments the temperature of the surface of the material is higher than the temperature in the reservoir and in particular, higher than the temperature in which the graphene molecular precursor starts to become chemically unstable (e.g., enabling the release of halide and / or hydrogen peripheral groups and the polymerization of the graphene layer). Thus, according to embodiments, the temperature maintained in the reservoir is higher than 70 °C, 90 °C, 110 °C, or 130 °C, and lower than 110 °C, 120 °C, 130 °C, or 150 °C. According to some embodiments, the temperature in the reaction chamber is not lower than 150 °C, not lower than 200 °C or not lower than 250 °C, and not higher than 500 °C, or not higher than 400 °C. In some embodiments the transformation into a graphene surface occurs instantly upon the deposition of the graphene molecular precursor, and in some embodiments, it occurs in a separate step. The transformation of the precursor into a surface may require energy which may be provided by heating or radiating the deposited molecular precursors.

[0098] According to some embodiments, the coated material may be a metal. According to some embodiments, the metal is one of copper, aluminum, ruthenium, gold, nickel, palladium, molybdenum, or cobalt. It will be clear to a person skilled in the art that with the appropriate selection of the first graphene molecular precursor, practically any metal can be selected in accord with process conditions (e.g., temperature or coating protocol).

[0099] According to some examples the material may be a non-metal such as a semiconductor, an oxide semiconductor (e.g., zinc oxide), a semiconductor oxide (e.g., silicon dioxide) or an organic polymer. According to some embodiments, metal coating of the non-metal material is configured according to the non-metal material. Thus, for example, if the non-metal material is a silicon substrate copper or gold may be excluded.

[0100] More Than One Molecular Precursor 14804-PC

[0101] According to some embodiments a thin film of molecular precursors is deposited through repeated release of several separate precursors, released into the reaction chamber and deposited consecutively from several reservoirs or concomitantly. According to such embodiments and in the case that more than one reservoir is used, each reservoir may be maintained at separate configured and operable temperature and pressure conditions and each graphene molecular precursor mixture may be injected into the reaction chamber independently by injection as disclosed hereinabove.

[0102] According to some embodiments the composition of the graphene molecular precursor coating on the surface is controlled by consecutive pulsated deposition. According to some embodiments at least two different graphene molecular precursors (which each may be a mixture) are deposited in a sequential manner. According to these embodiments a procedure for depositing the at least two different graphene molecular precursors is provided, the procedure may provide a list (periodic or nonperiodic) of separate deposition steps wherein in each step as one of the different graphene molecular precursors is deposited. Each of the thin layer deposition steps can be characterized by parameters comprising set temperatures of the chamber and of the respective evaporated graphene molecular precursor, by a respective valve opening period, enabling the vaporization and release of the respective graphene molecular precursor into the reaction chamber and by a wait / incubation period before opening the next respective valve. According to such embodiments, a heterogeneous molecular layer coating of graphene molecular precursors of substantially statistically uniform distribution is formed on the surface of the coated layer. According to some embodiments, the distribution statistics of the different graphene molecular precursors on the surface is affected by the molecular affinities between the different graphene molecular precursors and their respective kinetics.

[0103] Deposition According to some embodiments, thin layer deposition may be ALD, which in turn may be any one of thermal ALD, Plasma enhanced ALD (PEALD) also referred to as plasma-assisted ALD or radical-enhanced ALD, hot-wire ALD and photo assisted ALD. Advantages of these ALD processes include precise control the thickness, 14804-PC coverage and composition of the formed graphene molecular precursor layer / coating. According to some embodiments, the method is configured and adapted as a surface- driven process, in which surface reactions are dominant in the deposition process. As a result, the method enables excellent conformality and thickness control irrespectively of the substrate geometry, providing for uniform deposition of complex geometry with high aspect ratio (pattern depth to width ratio) and even on porous substrate surfaces.

[0104] According to some embodiments, the method can be carried out in a wide range of pressures, ranging from high vacuum to atmospheric pressure. According to some embodiments, surface reactions are substantially driven by thermal energy. Thus, according to some embodiments the method is carried out as an ALD process and is performed at chamber temperatures ranging from 100 °C, 150 °C, 200 °C or 250°C to 350 °C, 400°C or 450°C. According to some embodiments chamber temperatures are limited to these ranges. The advantage of limiting the temperature of the surface is to eliminate possible thermal damage to the surface and / or to prevent uncontrolled damage to the reacting moieties.

[0105] According to some embodiments, the ALD comprising an incubation period that may more than 5 seconds more than 20 seconds, more than 60 seconds, more than 180 seconds, or more than 600 seconds According to some embodiments the number of cycles used for the deposition of molecular precursors at a quantity fit to form one layer is more than 10, 50 or 100 cycles. According to some embodiments the number of cycles is less than 300 500 or 1000 cycles. According to some embodiments, pulses are arranged in bursts which comprise a small number of pulses with a short wait time between pulses (e.g., 1 sec) and a significantly longer wait time between consecutive bursts (e.g., 60 sec). According to some embodiments a higher hierarchy of pulse burst may be arranged allowing to more complex depositing recipes., e.g., forthe use of more than one molecular graphene precursor mixture or the use of longer wait between series of bursts.

[0106] According to some embodiments, the method is configured and adapted as a self-terminating process wherein process kinetics is limited, inter alia, by a limited 14804-PC number or reactants (graphene molecular precursors) or by the availability of active sites on the surface. According to some embodiments, such self-limiting improves the uniformity and conformality of the deposition of the graphene molecular precursors and the uniformity and conformality of the formed coating.

[0107] According to some embodiments, the invention provides a method for conformal coating wherein the coated surface comprises a patterned structure characterized by a GAR larger than 5, larger than 10 or larger than 30, wherein the GAR is measured with respect to the geometry of the coated pattern. According to some embodiments, coating conformality is characterized by the extent in which the coating maintains its thickness along the depth or height of the 3D patterns.

[0108] According to some embodiments, the surface has a patterned structure comprising at least one via or trench. According to some embodiments the surfaces may be the surfaces of an electronic chip at different stages of manufacturing and wherein the respective surfaces may be semiconductor surfaces, dielectric surfaces metal interconnect surfaces and composite damascene on to which the coating is being applied.

[0109] According to some embodiments, the ALD is PEALD, wherein the use of plasma during one of the reacting steps provides highly reactive species such as radicals that promote the growth of the deposited layer, this, in addition to the thermal energy from the substrate may enable the use of a wide range of molecular precursors and may provide for more efficient deposition and transformation of the deposited molecular precursors into a graphene layer. According to such embodiments, the bonding of the molecular precursors to the surface and / or the reactions between the molecular precursors to form the graphene coating may be based on reactions of the highly reactive species. Thus, according to some embodiments, PEALD may be performed at temperatures as low as room temperature. According to embodiments PEALD is performed at chamber pressure lower than IE-3 Torr.

[0110] According to some embodiments, the ALD is Hot-wire ALD wherein the ALD process employs a filament positioned in a filament zone and wherein the filament is 14804-PC heated up to a temperature of up to above 500 °C or above 1000 °C. According to such embodiments, at least one of the graphene molecular precursors or other moieties participating in the coating process, collectively dubbed, the molecular precursors, is directed to the reaction chamber through the filament zone to activate the respective molecular precursors which may be thermally excited or dissociated with. According to such embodiments, by tuning the temperature of the filament, the concentration of the thermally excited or dissociated molecules can be controlled.

[0111] As noted above, according to some embodiments, the ALD is photo-assisted ALD, in which, according to some examples photo-energy is absorbed by the graphene molecular precursors or by the substrate's surface to initiate and / or maintain the transformation of the deposited molecular precursor layer into a graphene coating. In some embodiments, photo-induced reactions are promoted by exposure of the reactants to ultraviolet (UV), visible range or infrared radiation. The interaction between reactant molecules and photons can result in the excitation and / or dissociation of the molecules into reactive species, which may lead to specific reactions at the surface of the substrate.

[0112] Peripheral Functional Groups

[0113] According to some embodiments, the at least one graphene molecular precursor comprises at least one compound bearing periphery functional groups on the periphery of the at least one compound. The formation of the carbon-carbon bonds between the graphene molecular precursors can be assisted by having the aromatic skeleton bear good leaving periphery functional groups, e.g., Y1and Y2groups on the periphery of the at least one compound. For example, Y1can be a halide such as -Cl or -Br and Y2can be a hydrogen -H, such that when the graphene precursor coating is transformed, a halide from one graphene molecular precursor and a hydrogen from another graphene precursor would leave as HCL or HBr and the two graphene molecular precursors would form a carbon-carbon bond. In another example, Y1can be -Cl and radiation of the graphene molecular precursor film generates carbon-carbon bonds between two carbons (which were linked to -Cl) of two adjacent (same or 14804-PC different) graphene molecular precursor molecules and a CI2 molecule is generated. The byproduct gas molecules that are generated can be removed from the system by vacuum.

[0114] In some embodiments Y1and Y2can be acidic and basic groups. The basic and acidic functional groups can be on the same compound (e.g., on different regions of the periphery of the carbon skeleton) or there may be a mixture of two different compounds which may be provided through separate molecular precursors (and optionally, through separate ALD cycles), one bearing acidic functional groups and the other bearing basic functional groups. According to some embodiments intermediate moieties may be formed during the deposition step (step 430).

[0115] According to some embodiments, a first and a second molecular precursors that have different periphery functional groups Y1and Y2are used, e.g., to control the uniformity and defect density of the formed graphene films. According to embodiments more than two graphene molecular precursors or mixtures thereof may be used. According to some embodiments, a catalyst may be incorporated into the process; during the series of pulses one or more pulses of the vaporized catalyst are inserted into the chamber and at least partially deposited on the surface of the substrate. According to such embodiments the catalyst may be a metal catalyst selected from Pd, Pt, Cu, Au, Ni, W and Co, or a mixture thereof.

[0116] The chamber can be kept at elevated temperature to ensure sufficient reaction rate. According to some embodiments the temperature of the surface of the material should be kept at temperatures higher than 150 °C, 200 °C or 250 °C.

[0117] According to some embodiments the graphene-metal composite is formed on a surface that is a patterned surface comprising 3D geometrical features having profile dimensions smaller than 100 nm. Such 3D geometrical features may include protrusions, trenches or vias, which in the case the product is an electric circuit or a VLSI chip, may form the structure in which the electric elements and their interconnects are formed. According to certain embodiments the graphene-metal composite is formed coating of the surface is performed in chip manufacturing and the graphene 14804-PC molecular precursor is deposited on a surface of a substrate that comprises an interconnect arrangement embedded in a top layer comprising a semi-conductor substrate (e.g., a silicon substrate) having electric circuit elements formed on its upper surface. This interconnect arrangement is sometimes referred to as 'damascene' or 'damascene wiring'.

[0118] According to some embodiments, the graphene molecular precursors may comprise several compounds wherein each in turn may comprise several of: (i) compounds A or B having tethering groups for covalently bonding to the surface and (ii) compounds C having no tethering groups. According to some embodiments the mol ratio between the combined amount of compounds A and B and the combined amount of compounds C being between 50:1 and 1:5000, preferably between 10:1 and 1:1000 and more preferably between 1:5 and 1:100. According to embodiments in which the graphene molecular precursor is a mixture of compounds, several compound mixtures may form the graphene molecular precursor and may be mixed in advance (concomitantly) or used consecutively in interspersed manner.

[0119] Transforming the Graphene Molecular Precursor into Graphene

[0120] According to some embodiments, the thin coating of molecular precursors is transformed into a graphene coating in parallel to the continued cycles of the thin layer deposition process through reactions of precursors between themselves and / or with the surface of the substrate. According to some embodiments the transforming of the molecular precursors into a graphene coating requires additional energy or external initiation.

[0121] Following the forming of the graphene molecular precursor layer / coating on top of the surface or in parallel to the depositing, transforming (polymerization) the deposited first graphene molecular precursor coating into a surface bound graphene layer, (step 440), is performed, to obtain a graphene coated surface comprising a graphene layer, wherein in some embodiments the formed graphene layer is bound to the surface of the material by covalent bonds and in some embodiments, by weak (e.g. adhesion) bonds. According to some embodiments, the formed graphene layer is an 14804-PC interfacial graphene layer, i.e., a one atom thick layer separating between different phases or materials. According to some embodiments the formed graphene layer comprises linkers, i.e., tethering groups that link the graphene layer to the surface of the substrate. According to some embodiments the formed graphene layer comprises free linkers, i.e., tethering groups that are not connected to the surface of the substrate and are positioned above the graphene layer. According to some embodiments these tethering groups may be adapted for forming bonds with an additional graphene layer. According to some embodiments these tethering groups may be adapted for forming bonds with a metal or a non-metal layer that will be deposited and formed on top of the formed graphene layer.

[0122] Thermal Considerations

[0123] According to some embodiments, the transforming of the graphene molecular precursors coating the surface is achieved by maintaining the surface at elevated temperature, preferably at temperatures higher than 150 °C, preferably at temperatures higher than 200 °C, and more preferably at temperatures higher than 250 °C.

[0124] According to some embodiments of the invention the process of the formation of the graphene interfacial layer or coating from graphene precursor is performed at relatively low temperatures, below 500 °C or below 400 °C and in some embodiments, below 350 °C below 300 °C, below 250 °C or below 200 °C. Process temperature may be controlled by controlling the temperature in a process chamber or by locally controlling the temperature in the region that is exposed to the radiation from the first radiation source and in particular by controlling the temperature in the graphene precursor layer region that is exposed to the radiation from the first radiation source. This can be performed for example by a second radiation source selected to locally irradiate in coordinated fashion said region of the graphene precursor layer radiated by the first irradiation source. The wavelengths of such second radiation source may be selected to have the absorption ratio (between absorption coefficient of the graphene precursor and the absorption coefficient of the surface material that is higher than 10, 14804-PC in some embodiments higher than 100 and in some embodiments, higher than 1000. An advantage of the use of a combination of localized heating and localized photoexcitation is the ability to precisely localize the formation of the graphene film.

[0125] Additionally, or alternatively, the temperature in the reaction chamber during the polymerization process is monitored by common methods available in the art, for example, by positioning, on the metallic surface, labels containing photo thermal switching dyes, indicative of the maximal temperature on the surface. An example of such labels are non-reversible temperature labels marketed by Omega Engineering Inc. of Norwalk, CT, USA. An infra-red camera or a thermocouple may also be used to monitor the temperature as known in the art.

[0126] ALD of The Metals

[0127] According to a further aspect of the method, metal is deposited on the top surface of the formed graphene layer (step 450). According to some embodiments, metal is deposited by ALD. Numerus methods for metal ALD are known in the art these include the use of hydrogen gas as the co-reactant, which for example, in the case of copper may be performed at temperatures below 100 °C or the use of fluorosilane elimination reactions using a metal halide and a silicon precursor (e.g. SiFU, SizHe) as the reactants. According to some embodiments, the ALD is hot-wire ALD or PEALD. As is evident to a person practiced in the art, various known metal ALD methods may be adapted and incorporated in step 450. According to some embodiments, the metal may be selected from copper, aluminum, nickel alloy, ruthenium, gold, palladium, molybdenum, tungsten or cobalt or a combination thereof. According to some embodiments step 450 comprises depositing a first metal to obtain a metal layer of a first metal and depositing a second metal to obtain a metal layer of a second metal. According to some embodiments at least one of the metal depositions is performed by hot wire ALD or PEALD.

[0128] According to some embodiments, the graphene-metal composite comprises a first metal layer comprising one or more metals and a second metal layer comprising one or more metals wherein the one or more metals of the first metal layer are same 14804-PC or different from the metals of the second metal layer. According to some embodiments, the first metal layer and the second metal layer are disposed between the same two graphene layers. According to some embodiments, the graphene-metal composite comprises a heterogeneous metal layer having mol ratio between at least two different metals which differ from their relative electric potential or relative atom size.

[0129] Nano Clusters

[0130] According to some embodiments, the metal layer is in the form of nanoclusters. The formation of nanoclusters may be performed by self-limiting the deposition of a metal on top of a graphene layer. According to some embodiments nanoclusters of metal atoms are formed at preconfigured temperature conditions or at a preconfigured temperature conditions variation profile of the ALD. According to the embodiments the preconfigured temperature conditions or the preconfigured temperature conditions variation profile is within the ALD preconfigured temperature range i.e., between 100°C and 450°C. Thus, according to some embodiments, the graphene-metal composite comprises graphene layers and at least one metal layer, at least one metal layer being disposed between two graphene layers, wherein the metal layer is in the form of nanoclusters. According to some embodiments the nanoclusters may be of one or more types characterized by their composition and size.

[0131] General Properties of The Graphene-Metal Composite

[0132] According to some embodiments, the graphene-metal composite excludes a graphene-metal composite comprising a covalent, ionic or coordinate bond between a metal layer and a functional group of the graphene layer. According to some embodiments, the graphene-metal composite excludes a graphene-metal composite comprising a covalent, ionic or coordinate bond between a functional group of the graphene layer and the substrate.

[0133] The graphene-metal composite may have higher conductivity than the conductivity of the corresponding metal doped graphene ribbon (the graphene ribbon 14804-PC doped with the same metal. According to some embodiments, the graphene-metal composite comprises graphene layers and metal layers, at least one metal layer being disposed between two graphene layers, wherein at least one metal layer is ferromagnetic.

[0134] Raman Monitoring

[0135] According to certain embodiments, the formation of the graphene layer or coating orthe formation of the metal layer may be monitored by Raman spectrography. According to such embodiments, a radiation source is used to generate Raman scattering, typically in the visible or IR wavelength range. In the of monitoring the formation of the graphene coating, Raman scattering is used to characterize the presence of graphene and may provide signals indicative of the regions comprising the un-polymerized graphene precursor layer. Accordingly, in some embodiments, Raman scattering signal indicative of a presence of a full layer of graphene within a detected region (or indicative of elimination of the graphene precursor) is used to indicate the state of the polymerization of graphene precursor layer and when appropriate, to arrest the radiation of light of the first or second source which, in some embodiments, drive the generation of the graphene interfacial layer or coating. According to some embodiments, Raman spectra may also be used to monitor the quality of the formed graphene film using for example the intensity ratio of the respective spectral lines / peaks indicative of the formation of the graphene layer and the exhaustion of the precursor. As for example disclosed in Araujo P. T. et al. Materials Today 2012, 15, 98- 109, defect density (number of defects per cm2) may be estimated directly from this ratio. Alternatively, coverage ratio or coverage continuity of the graphene film may be used to quantify its quality, measuring the percentage of the area of the graphene film that is without defect. However, this measure should be used carefully in the right context as for example, in large, say 100 cm2, transparent electrode 99% coverage can be a 1 cm2hole (a single discontinuation) or a hundred 1 mm2separate holes - two extreme cases which might have very different implications on the quality of the product. According to certain embodiments, Raman scattering which is dependent on the temperature of the scattering material is used to probe the temperature of the 14804-PC irradiated graphene precursor layer or the formed graphene layer or coating, to monitor and control their respective temperatures, thereby enabling better control of process temperature and higher, more repeatable quality of the formed graphene layer coating.

[0136] Other spectroscopic methods known in the art may additionally or alternatively be used to monitor the formation of the graphene layer or the metal layer.

[0137] Defects Ratios and Component Ratios

[0138] According to some embodiments, the first graphene layer is formed on an exposed surface of a material to form a graphene coating covering more than 90%, more than 95% or more than 99% of the exposed surface onto which the graphene molecular precursors are being deposited. According to some embodiments, the ratio of defects in the formed graphene interfacial layer or coating may be controlled by controlling the depositing conditions and / or the ratios of different graphene molecular precursors. In some embodiments, the used graphene molecular precursor comprises compounds without tethering groups or a reduced ratio of compounds that have tethering groups leading to a reduced ratio of defects in the manufactured graphene interfacial layer or coating. Further, the use of use graphene molecular precursor comprising a compound without tethering groups may reduce steric effects and allow for better packing of the graphene molecular precursors on the surface further reducing the ratio of potential defects in the graphene layer. The larger the ratio of the compound without tethering groups will result in a lower defect density. Controlling other ALD conditions such as temperature profile or pulsing profile (e.g., pulse duration and repetition rate) may further reduce the number of potential defects. According to some examples the ratio of defects in the graphene layer is less than 1E12 defects per cm2, according to some embodiments less than 1E11 defects per cm2or less than 1E10 defects per cm2.

[0139] Additional Graphene Layers 14804-PC

[0140] After completing a graphene layer, e.g., a first graphene layer, a further graphene layer or layers may be deposited on top of the first graphene layer before a metal layer is deposited. To this end, a new layer of graphene molecular precursors, being the same or different from the graphene molecular precursors of the preceding layer may be deposited on top of the formed graphene layer or coating wherein the graphene coating is substantially similar in its properties (e.g., mechanical properties) and optionally different in the tethering groups or defect and edge properties. According to some embodiments, some properties of adjacent graphene layers may be different due to different interactions with adjacent coupled layers (graphene layers or metal or non-metal surfaces), or due to different defect densities or different tethering ratios and their respective characteristics. According to some embodiments, tethering groups protruding from the formed graphene layer are configured and adapted to bond with graphene molecular precursors that are deposited in a following step to form the adjacent layer graphene layer.

[0141] According to some embodiments, a metal coating is formed on top of the graphene layer that comprises tethering groups which are connected to the graphene layer, and which are conformationally oriented perpendicularly to the local main plain of the graphene layer. Thus, the tethering groups are integrated in the metal layer, forming local disruptions in the metal layer and / or protruding through it. According to some embodiments, graphene molecular precursors are deposited on top of the metal layer that comprises the integrated or protruding tethering groups. . According to such embodiments, during transforming of the graphene molecular precursor layer into a top graphene layer, bonds are formed between the graphene molecular precursors and the tethering groups, forming bonds between the graphene layers and comprising an intermediate thin metal layer.

[0142] Thus, if for example the first graphene layer is formed on a metal layer, the molecular precursor groups used in forming this layer will be selected and configured to coat a metal surface and if a second graphene layer will be formed directly on top of the first graphene layer the graphene molecular precursors will be configured and selected to be compatible with a graphene surface. Further, graphene molecular 14804-PC precursor used in forming the first layer according to this example may comprise tethering groups configured to bond to the metal surface and to graphene molecular precursor selected for forming the second layer and graphene molecular precursor selected for forming the second graphene layer may comprise tethering groups configured to bond to the graphene layer on to which they are deposited. Additionally, if for example a third graphene layer should be formed and if a metal layer is to be formed between the second and the third graphene layers then the graphene molecular precursors used in forming the second layer may be additionally configured to comprise tethering groups that would protrude from the formed graphene layer, e.g. due to steric constraints, to enable bonding of the second graphene layer to the third graphene layer, generally, as describes with respect to embodiments disclosed above.

[0143] The deposition and transforming process for generating the graphene layer and the process of metal deposition can be iterated as much as needed in order to obtain a desired number of graphene layers or coatings. The graphene molecular precursors can be the same or different in each iteration. According to some embodiments the method further comprises the steps of obtaining a second graphene molecular precursor, depositing of said second graphene molecular precursor on top of the first graphene coated material, or on top of the metal layer, and transforming the deposited graphene molecular precursor to a top graphene coating. According to some embodiments, these steps are repeated, as indicated by arrow 480 in Figure 5, to obtain a graphene coating comprising at least three graphene coatings and at least one metal layer. As would be evident, not all steps of the process need to be repeated, and some metal layer or graphene layer can be formed in sequence without interleaving a respective complementary graphene or metal layer. For example, the number of graphene layers may be 6 layers while the number of interleaved metals layers may be 2. According to some embodiments the number of graphene layers formed in the thus repeated process is 2 to 12 graphene coating layers, according to some embodiments the number is 2 to 6. According to some embodiments the number of intermediate metal layers is at least 2, at least 4 or at least 8. According to some embodiments, a 14804-PC metal layer of the first metal is deposited on top of a first graphene layer and the metal layer of the second metal is deposited on top of a second graphene layer.

[0144] According to some embodiments, during depositing of the graphene molecular precursor the conditions for transforming are maintained (e.g., maintaining elevated temperature within the reaction chamber) and transforming the precursor deposited onto the surface is performed in parallel to the ongoing depositing of the graphene molecular precursor.

[0145] Applications

[0146] According to some embodiments, the surface of the material is a metal surface, and the coating is performed on the metal surface. According to some embodiments the surface of the material is a non-metal surface, and the coating is performed on the non-metal surface. According to some embodiments the graphene-metal composite is for use in a wide range of applications such as, without wishing to be limited thereto, an interconnection in a device selected from the group consisting of back end of lines (BEOL), nano-electro-mechanical device, photovoltaic cells, Organic LED and transparent conductive electrodes, electro-optical sensors, and graphene transistors, or high conduction interconnects.

[0147] The description of the present invention has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Embodiments were chosen and described to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. 14804-PC

[0148] The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims appended to this specification are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

[0149] References in the specification to "one embodiment", "an embodiment", etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to combine, affect or connect such aspect, feature, structure, or characteristic with other embodiments, whether or not such connection or combination is explicitly described. In other words, any element or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility between the two, or it is specifically excluded.

[0150] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely," "only," and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms "preferably," "preferred," "prefer," "optionally," "may," and similar terms are used to indicate that an item, condition, or step being referred to is an optional (not required) feature of the invention.

[0151] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated.

[0152] As will be understood by one skilled in the art, for all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual 14804-PC values making up the range, particularly integer values. A recited range (e.g., weight percent or carbon groups) includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc.

[0153] As will also be understood by one skilled in the art, all ranges described herein, and all language such as "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number(s) recited and such terms refer to ranges that can be subsequently broken down into sub-ranges as discussed above.

[0154] Examples

[0155] Examples are provided for different steps as disclosed, e.g., with respect to Figure 5.

[0156] Example 1

[0157] ALD can be used to deposit the graphene molecular precursor mercaptomethylenelhexabenzocoronene metal wafer a metal interconnect net patter embedded on a dielectric or semi-conductor wafer. ALD in a Savannah® 100 Veeco is exemplified. A solution of the graphene molecular precursor in xylene is placed in a reservoir. A ruthenium wafer, copper wafer and cobalt wafer are placed in the reactor. Temperatures in the precursor reservoir, the manifold leading from the reservoir to the reaction chamber and in the reaction chamber are respectively set to 130°C, 150°C and 250°C and stabilized for 10 minutes with 20 seem nitrogen flow. Depositing repeated 100 times ("Cycles"). During each cycle the precursor valve is opened for 0.015 sec ("pulse") and then waiting for exposure 60 sec before evacuating and cleaning with N2 flow.

[0158] Graphene synthesis can be performed by maintaining the thin film of the graphene molecular precursor at 250 °C for 60 minutes. Consequently, the ruthenium, 14804-PC copper and cobalt wafers are each covered by the graphene film wherein the surface of the metal wafer is covalently connected to the interfacial graphene layer film.

[0159] Characterization of the coated wafers is conducted by XPS and Raman spectroscopy.

[0160] Example 2

[0161] ALD can be used to deposit the graphene molecular precursor comprising a mixture of 1:100 mercaptomethylene-hexabenzocoronene / octachloropyrene onto a metal wafer or metal interconnect net pattern embedded on a dielectric or semiconductor wafer following mutatis mutandis the same procedure and conditions as described in Example 1. The graphene molecular precursor can be applied by placing a 1:100 mercaptomethylene-hexabenzocoronene / octachloropyrene solution in xylene in the reservoir. Alternatively, the deposition of each component of the graphene molecular precursor can be performed sequentially. Following the deposition of the mercaptomethylene-hexabenzocoronene at the conditions detailed above, the process can be repeated at the same conditions with the octachloropyrene, having the latter fill in voids which are left after the deposition of the former.

[0162] Consequently, the metal wafer or metal interconnect net pattern embedded on a dielectric or semi-conductor wafer is covered by the graphene film wherein the surface of interconnect net pattern being covalently connected to the interfacial graphene layer film.

[0163] ALD is used to deposit the graphene molecular precursor comprising a mixture of 1:100 mercaptomethylene-hexabenzocoronene / octabromopyrene onto an interconnect net pattern following the procedure above.

[0164] Characterization of the coated wafers is conducted by XPS and Raman spectroscopy.

[0165] Example 3

[0166] ALD is used to deposit a thin metal layer on top of the graphene layers formed on a metal substrate. To create a uniform thin metal layer on top of the graphene by ALD, functional groups on the graphene surface are used; tethering groups that provide 14804-PC functional groups. Additionally, or alternatively, O3 pre-treatment is used to mildly oxidize the graphene and leave epoxide (C-O) carbonyl (C=O) and carboxyl (O-C=O) groups on the graphene surface.

[0167] Ruthenium organometallic complex; r|4 -2,3-dimethylbutadiene Ruthenium tricarbonyl (Ru(DMBD)(CO)3) as a Ru precursor is used to deposit Ru thin layer on top of the graphene layers using Savannah® 100 Veeco. The decomposition of the Ruthenium organometallic complex by H2O follows procedures such as the procedure referred to in "Thermal atomic layer deposition of ruthenium metal thin films using nonoxidative coreactants" by S. Cwik et. al., published in J. Vac. Sci. Technol. A 2020, 38, 012402; doi: 10.1116 / 1.51251090.

[0168] RU(DMBD)(CO)3 as Ru precursor is placed in a reservoir, and a sample with graphene layers is placed in the reactor. Temperature in the reaction chamber is set to between 160°C and 210°C and stabilized for 20 minutes with 20 seem nitrogen flow. After optional O3 pre-treatment of the graphene layer, the Ru organometallic is repeatedly deposited in "pulses" and treated to decompose the complex:

[0169] 1. A pulse of Ru(DMBD)(CO)3 is inserted into the chamber. Pulse length is determined by the pulse length required to reach surface saturation. To ensure the deposition of the Ru organometallic complex on the functionalized graphene surface sufficient wait time (e.g., 30 sec) is used between cycles.

[0170] 2. Next, the reactor is evacuated and cleaned with N2 flow for 10 sec.

[0171] 3. Following the evacuation step a pulse of H2O is provided with a, and waiting cycle for exposure and decomposition of the organometallic complex.

[0172] 4. Next, the reactor is evacuated and cleaned with N2 flow.

[0173] Characterization of the oxidized graphene can be conducted by XPS and Raman spectroscopy, and the metal coated sample can be characterized using XPS, SEM, TEM.

Claims

14804-PCCLAIMS1. A graphene-metal composite comprising at least two graphene layers and at least one metal layer being disposed between two graphene layers, characterized by at least one of:• any one of the metal layers is essentially free of residuals selected from the group consisting of water, organic solvents, metal oxides, metal halides, halides, halogen molecules, and organo-metallic compounds;• at least one metal layer having layer normalized spatial thickness deviation lower than 10%;• at least one metal layer covering at least 90% of an adjacent one of the at least two graphene layers; and• graphene layer defect density lower than lell defects per cm2.

2. The graphene-metal composite according to claim 1 wherein the graphenemetal composite is a coating of a surface.

3. The graphene-metal composite according to claim 2 wherein the graphenemetal composite is a coating of a patterned surface having surface conformality.

4. The graphene-metal composite according to claim 3 and wherein surface conformality is characterized by GAR-PD50 > 3.

5. The graphene-metal composite according to claim 3 wherein the surface pattern has pattern features smaller than 500 nm.

6. The graphene-metal composite according to claim 3 wherein the patterned surface is the surface of a lithographically etched substrate.

7. The graphene-metal composite according to claim 1 wherein at least two graphene layers are interlayered with at least one metal layer.

8. The graphene-metal composite according to claim 1 wherein the thickness of at least one metal layer is monoatomic.

9. The graphene-metal composite according to claim 1 wherein the metal layer is a heterogeneous metal layer comprising at least two metals.

10. The graphene-metal composite according to claim 1 comprising a first metal layer comprising one or more metals and a second metal layer comprising one14804-PC or more metals wherein the one or more metals of the first metal layer are same or different from the metals of the second metal layer.

11. The graphene-metal composite according to claim 10 wherein the first metal layer and the second metal layer are disposed between the same two graphene layers.

12. The graphene-metal composite according to any one of claim 1 to 11 comprising a heterogeneous metal layer having mol ratio between at least two different metals which differ from their relative electric potential or relative atom size.

13. The graphene-metal composite according to any one of claim 1 to 12 excluding a graphene-metal composite comprising a covalent, ionic or coordinate bond between a metal layer and a functional group of the graphene layer.

14. The graphene-metal composite according to claim 13 excluding a graphenemetal composite comprising a covalent, ionic or coordinate bond between a functional group of the graphene layer and the substrate.

15. The graphene-metal composite according to any one of the preceding claims, wherein the metal in between the graphene layers is, aluminum, nickel alloy, ruthenium, palladium, molybdenum, tungsten, cobalt, or mixtures thereof.

16. The graphene-metal composite according to any one of the preceding claims, wherein two alternating layers of graphene are bound to each other by a linker covalently bound to the two alternating graphene layers.

17. The graphene-metal composite according to any one of the preceding claims, wherein the graphene-metal composite has conductivity higher than the conductivity of the corresponding metal doped graphene ribbon.

18. The graphene metal composite according to any one of the preceding claims wherein a top graphene layer of the graphene-metal composite is bound to a surface of a material deposited on top of said top graphene layer.

19. The graphene metal composite according to any one of the preceding claims, wherein the metal layer is in the form of nanoclusters.

20. A graphene-metal composite comprising graphene layers and at least one metal layer, at least one metal layer being disposed between two graphene layers, wherein the metal layer is in the form of nanoclusters.14804-PC21. A graphene-metal composite comprising graphene layers and metal layers, at least one metal layer being disposed between two graphene layers, wherein any one of the metal layers is essentially free of residuals selected from the group consisting of water, organic solvents, metal oxides, metal halides, halides, halogen molecules, and organo-metallic compounds.

22. The graphene metal composite according to claim 21 wherein the residual concentration is in trace concentration in the graphene-metal composite and wherein the concentration ratio of any of said residual to the number of metal atoms is being lower than IE-4.

23. A graphene-metal composite comprising graphene layers and metal layers, at least one metal layer being disposed between two graphene layers, wherein at least one metal layer is ferromagnetic.

24. A graphene-metal composite comprising graphene layers and metal layers, at least one metal layer being disposed between two graphene layers, wherein the thickness of the metal layer is larger than 0.34 nm.

25. A device comprising the graphene metal composite as in any one of the preceding claims.

26. A method for producing a graphene-metal composite comprising the steps of depositing a molecular graphene precursor on a surface; transforming said deposited molecular graphene precursor into a graphene layer; depositing a metal on top of the graphene layer to obtain metal layer deposited on the graphene layer depositing a moleculargraphene precursor on top of the metal layerand transforming the molecular graphene precursor into a graphene layer on top of the metal layer, to obtain a metal graphene composite.

27. The method according to claim 26 wherein forming the graphene-metal composite conductor further comprises repeating steps of depositing a metal layer, depositing molecular graphene precursors and transforming the latter into graphene to obtain a graphene-metal composite, said graphene-metal composite comprising at least 3 graphene layers.14804-PC28. The method according to claim 26 or 27 wherein the surface is a patterned surfaces comprising 3D geometrical features having profile dimensions smaller than 100 nm.

29. The method according to claim 26 wherein the depositing is by atomic layer deposition or by molecular layer deposition.

30. The method according to any one of claims 26 to 29 wherein the metal is copper, aluminum, nickel alloy, ruthenium, gold, palladium, molybdenum, tungsten or cobalt.

31. The method according to any one of claims 26 to 30 comprising depositing a first metal to obtain a metal layer of a first metal and depositing a second metal to obtain a metal layer of a second metal.

32. The method according to claim 31 wherein the metal layer of the first metal is deposited on top of a first graphene layer and the metal layer of the second metal is deposited on top of a second graphene layer.

33. The method to any one of claims 26 to 32 wherein transforming comprises maintaining the surface coated with the graphene precursor at a temperature higher than 150 °C.

34. The method to any one of claims 26 to 33 further comprising maintaining the temperature of the non-metallic surface at below 400 °C.

35. The method according to any one of claims 26 to 34 further comprising detecting the Raman scattering while radiating with a second radiation source, IR light, characterizing presence of graphene, the Raman scattering is indicative of a presence of a full layer of graphene (ii) measuring contact angle of the surface and (iii) detecting fluorescence of the surface by a fluorescence microscope.

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