Methods for forming graphene-containing devices

Abstract

The present invention relates to a method for forming a graphene-comprising device (5), comprising the steps of: forming a graphene film (1) on a substrate (2) S1; depositing on the graphene film (1) a functionalization material (3) configured to modify the physicochemical properties of the graphene film (1), the deposition of the functionalization material being configured to partially cover the graphene film (1); vapor-phase depositing S3 of a polymeric material (4) covering the graphene film (1) and the functionalization material (3); and removing S4 of the substrate (2) such that the polymeric material (4) forms a support for the graphene film (1).

Description

[Technical field]

[0001] The present invention relates to the field of methods for forming devices comprising graphene, in particular to methods for forming devices comprising functionalized graphene, for example by placing the graphene in contact with an object that allows functionalization, in particular by doping, on its rear surface. [Background technology]

[0002] Graphene is a material composed of carbon atoms that form a crystal lattice one atom thick. More specifically, multi-layer graphene is a compact stack of two to typically ten layers of single-layer graphene. Graphene is particularly advantageous in applications where a semiconductor with high electron mobility is desired to detect the movement of charge in the environment and convert it into a change in the electrical conductivity of the graphene surface. Most electronic applications of graphene require a continuous macroscopic layer of graphene, composed of one or several layers of carbon atoms, which is transferred onto a substrate made of a material selected for the specific application. Continuous graphene is typically synthesized using chemical vapor deposition (a technique also known as CVD by those skilled in the art), where graphene is crystallized on a catalytic base substrate such as copper foil at the scale of one to several atomic layers. The carbon of graphene is supplied from precursor gases such as methane or other hydrocarbons.

[0003] It remains difficult to remove a graphene layer from a base substrate and transfer it onto a target substrate, the surface of which is an electrical insulator, without structurally damaging or contaminating the two surfaces of the graphene layer and / or degrading its electronic properties, such as electrical conductivity and charge carrier mobility.

[0004] It is also difficult to deposit entities on one side of graphene without damaging or contaminating the overlying graphene layer and / or reducing its electronic properties, especially its sensitivity to the environment, in order to functionalize it, in particular by doping or the proximity effect.

[0005] Graphene is functionalized by a functionalizing material in contact with or in close proximity to the graphene that either changes the physicochemical properties (such as electronic, optical, mechanical, chemical properties) of the graphene film or alters the surrounding environment of the graphene film by shielding, filtering, or influencing at a distance.

[0006] Therefore, there is a need for a method of forming a functionalized graphene-containing device that preserves the structural and electronic integrity of the graphene layer and reduces the degree of contamination of the exposed surface while exposing its cleanest surface, i.e., the surface in contact with the catalytic substrate, to the environment. Summary of the Invention

[0007] The present invention aims to propose a method for the formation of a device comprising functionalized graphene, which overcomes the problems of the prior art.

[0008] The object of the present invention is to provide a method for forming a device comprising graphene, comprising the steps of: forming a graphene film on a substrate; depositing a functionalization material on the graphene film, the functionalization material being configured to modify a physicochemical property of the graphene film, the deposition of the functionalization material being configured to partially cover the graphene film such that at least a portion of the graphene film is not covered by the functionalization material; vapor-depositing a polymeric material covering the graphene film and the functionalization material such that the polymeric material contacts at least a portion of the graphene film that is not covered by the functionalization material; and removing the substrate so that the polymer material forms a support for the graphene film.

[0009] In this method, the integrity of the graphene film is not compromised by the various deposition and removal steps. When the substrate is removed, the graphene surface is exposed, which is uncontaminated since it was in contact with the substrate. The polymer material directly contacts the rear face of the graphene film and functionalizes it. The exposed (free) face of the graphene is uncontaminated and clean. The challenge of functionalizing graphene while preserving the quality of the graphene layer and ensuring that one of the two faces is free of surface contamination is achieved. This functionalization allows interaction with elements in the vicinity of the graphene film in the fluid that is deposited on the graphene.

[0010] Such a method is advantageously and optionally complemented by the various following features, taken alone or in combination:

[0011] The functionalizing material is deposited on the graphene film in the form of elements that have an average thickness perpendicular to the graphene film and an average lateral extent in a plane parallel to the graphene film. The graphene film has a front surface and a rear surface opposite the front surface at the end of the step of removing the substrate. The rear surface is in contact with the functionalized material and the polymeric material. The front surface is a free surface and has a roughness that is less than the average thickness of the elements of functionalizing material. Roughness is determined relative to a flat surface, where roughness is equal to the standard deviation of the front height in the vertical direction as a function of position in the plane of the graphene film, the front height being defined relative to an area in the plane that is greater in size than the average lateral extent.

[0012] The roughness relative to the reference surface is less than 10% of the average thickness, preferably less than 5% of the average thickness.

[0013] The polymeric material includes parylene.

[0014] The functionalization material is deposited in the form of metal nanowires, and / or in the form of semiconductor nanowires or semiconductor quantum dots, and / or in the form of magnetic metal nanoparticles, and / or in the form of patterned metal thin films, and / or in the form of dielectric layers deposited by atomic layer deposition (ALD), and / or in the form of boron nitride layers deposited by chemical vapor deposition (CVD).

[0015] The present invention also relates to a graphene-containing device, the device comprising: a graphene film partially covered by a functionalization material configured to modify an electrical or magnetic property of the graphene film; and a polymeric material covering the graphene film and the functionalization material such that the polymeric material is in contact with at least a portion of the graphene film that is not covered by the functionalization material.

[0016] Such a device is advantageously and optionally complemented by various features:

[0017] The functionalizing material is composed of elements that have an average thickness perpendicular to the graphene film and an average lateral extent in a plane parallel to the graphene film. The graphene film has a front surface and a rear surface opposite the front surface. The rear surface is in contact with the functionalized material and the polymeric material. The front surface is a free surface and has a roughness that is less than the average thickness of the elements of functionalizing material. Roughness is determined relative to a flat surface, where roughness is equal to the standard deviation of the front height in the vertical direction as a function of position in the plane of the graphene film, the front height being defined relative to an area in the plane that is greater in size than the average lateral extent.

[0018] The roughness relative to the reference surface is less than 10% of the average thickness, preferably less than 5% of the average thickness.

[0019] The polymeric material includes parylene.

[0020] The functionalization material is present in the form of metal nanowires, and / or in the form of semiconductor nanowires or semiconductor quantum dots, and / or in the form of magnetic metal nanoparticles, and / or in the form of patterned metal thin films, and / or in the form of dielectric layers deposited by atomic layer deposition (ALD), and / or in the form of boron nitride layers deposited by chemical vapor deposition (CVD).

[0021] Other characteristics and advantages of the invention will become apparent from the following description, given by way of example and not of limitation, and read with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of a method for forming a graphene-containing device according to one embodiment of the present invention; [Diagram 2] 1A-1D are schematic diagrams illustrating steps in a method of forming a device according to an embodiment of the present invention. [Figure 3A] 1A-1D are schematic diagrams illustrating steps in a method of forming a device according to an embodiment of the present invention. [Figure 3B] 1A-1D are schematic diagrams illustrating steps of a method for forming a device according to an embodiment of the present invention; [Figure 3C] 1A-1D are schematic diagrams illustrating steps of a method for forming a device according to an embodiment of the present invention; [Figure 3D] 1A-1D are schematic diagrams illustrating steps in a method of forming a device according to an embodiment of the present invention. [Figure 4] 1A-1D are schematic diagrams illustrating steps in a method of forming a device according to an embodiment of the present invention. [Diagram 5] 1A-1D are schematic diagrams illustrating steps in a method of forming a device according to an embodiment of the present invention. [Figure 6] 2 is a schematic diagram of a device obtained by a formation method according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Methods for forming graphene-containing devices A method of forming a graphene-containing device is shown with reference to Figure 1. Figure 1 shows a cross-sectional view of a graphene device during fabrication.

[0024] In a first step S1, a graphene film 1 is formed, for example by chemical vapour deposition (CVD), on a substrate 2, for example made of copper.

[0025] Here, the substrate 2 serves as a growth substrate.

[0026] The substrate can be formed from materials other than copper, including metals such as nickel, cobalt, ruthenium, copper alloys such as alloys of copper and nickel, copper and cobalt, and copper and ruthenium, and dielectric materials such as zirconium oxide, hafnium oxide, boron nitride, and aluminum oxide.

[0027] Step S1 may in particular be carried out in a growth furnace.

[0028] The substrate 2 may be a foil, as shown in Figure 1. The foil has a thickness of 100 nm to 100 µm, but a thickness of about 1 cm to 10 cm is also possible.

[0029] The substrate 2 may be a laminate of a reactive layer (such as copper) and a refractory layer (such as alumina). If ultra-fine layers of copper (eg 200 nm) are used, a multi-layer substrate is required.

[0030] The thickness of the graphene film 1 is, for example, one atom to eight atomic layers, and can be adjusted depending on the application and the desired electronic properties.

[0031] The formation of graphene films on substrates is described in French patent application FR 3 033 554 A1.

[0032] The surface of the graphene film 1 facing the substrate 2 is called the front surface, and the surface opposite to the front surface of the graphene film 1 is called the rear surface. The rear surface is a free surface, in other words, an uncovered surface, at the end of step S1.

[0033] In a second step S2, a functionalization material 3 configured to modify the physicochemical properties of the graphene film is deposited on the graphene film so as to partially cover the graphene film.

[0034] The deposition is arranged so that at least a portion of the graphene film 1 is not covered by the functionalization material 3 .

[0035] Functionalization can be achieved directly by physical bonding of the functionalization material to the graphene through contact, or indirectly by remote influences (e.g., electric or magnetic fields).

[0036] A functionalization material 3 is deposited on the rear surface of the graphene membrane and is in direct contact with the graphene membrane at the end of step S2.

[0037] The functionalization material 3 only partially covers the rear surface of the graphene membrane 1 such that at least a part of the rear surface is free, in other words at least a part of the rear surface is not covered by the functionalization material. Preferably, 5% or more of the rear surface of the graphene membrane is kept free during deposition of the functionalization material. More preferably, 10% or more of the rear surface of the graphene membrane is kept free during deposition of the functionalization material.

[0038] The functionalization material partially covers the graphene, allowing a polymer to be deposited later on the functionalization material and graphene while maintaining adhesion between the graphene and the polymer.

[0039] The thickness of the functionalization material deposited in step S2 is typically 10 nm.

[0040] The thickness of the functionalizing material can typically be from 0.1 nm to 1 mm.

[0041] The types and morphologies of functionalizing materials that can be deposited are discussed in more detail below.

[0042] To protect the components from contamination of the rear surface of the graphene film and oxidation of the substrate, step S2 can be performed under a protective atmosphere.

[0043] For the same purpose, it is useful to perform step S2 quickly after step S1 has been performed.

[0044] In a third step S3, a polymer material 4 is vapor-deposited over the graphene film 1 and the functionalization material 3. In particular, the polymer material 4 is in contact with at least a part of the graphene film 1 that is not covered by the functionalization material 3.

[0045] The deposition of the polymer material is performed on the rear side of the graphene membrane, in other words, the polymer material is deposited on the parts of the rear side of the graphene membrane 1 that are not covered with material and on the functionalization material deposited in step S2, thereby forming a layer of polymer material on the rear side of the graphene membrane.

[0046] The polymeric material has an inner surface in contact with the graphene rear surface and the functionalized material, and an outer surface opposite the inner surface. The outer surface is a free surface.

[0047] The deposition of the polymer material may be performed to produce a layer thickness of the polymer material that is much larger than the thickness of the functionalized material deposited at the end of step S2, such that the shape of the outer surface of the polymer material deposited at the end of step S3 is independent of the irregularities formed by step S2, in particular the rear surface of the graphene and the functionalized material partially covering it.

[0048] Step S3 can be configured so that the outer surface is flat and parallel to the graphene film.

[0049] The layer thickness of the polymer material can be between 100 nm and 50 μm.

[0050] An example of a polymeric material is poly(para-xylylene), also known as n-xylylene or parylene.

[0051] Parylene is a biocompatible material.

[0052] Parylene also has the advantage that it can be evaporated in the gas phase, forming a conformal layer on the coated surface regardless of horizontal or vertical orientation.

[0053] Moreover, this method of forming the parylene layer can be carried out at room temperature, i.e. 20-30 °C. Therefore, there is no risk of damaging the functionalization material deposited on the graphene film. This makes it possible to encapsulate temperature-sensitive functionalization materials, for example one or more biological substances.

[0054] Parylene also contains aromatic functional groups that interact strongly with graphene, providing important adhesion between the two materials.

[0055] Finally, Parylene has the advantage that it can be stretched up to 200% before breaking and remains flexible over a relatively wide temperature range. By way of example, the polymeric material may include Parylene C or Parylene N. Both Parylene C and Parylene N have the advantage of being relatively elastic, although Parylene N has a slightly lower Young's modulus and is more elastic than Parylene C.

[0056] In a fourth step S4, the substrate 2 is removed. This results in a device blank 5 consisting of the graphene film, the functionalization material 3 and the polymer layer 4.

[0057] The front side of the graphene film is exposed or free, i.e., it is not covered and is in direct contact with the outside air and can be contacted with the object to be characterized.

[0058] The rear surface of the graphene film is in contact with a functionalization material that imparts a specific function to the graphene.

[0059] Both the graphene film and the functionalization material are held by a layer of polymer material.

[0060] The deposition of the polymeric material allows to retain the functionalizing material that functionalizes the graphene while maintaining good adhesion, high flexibility of the graphene surface, and large-scale electronic continuity of the graphene. In particular, the method does not damage the structure of the graphene film and the front surface of the graphene film is clean and free of contamination. Thus, surprisingly, even if the functionalizing material does not have adhesive properties to the graphene and / or the polymeric material, the bonding of the polymeric material to the graphene in the areas vacated by the deposition of the functionalizing material alone can ensure good mechanical adhesion of the stack of the graphene film, the functionalizing material, and the polymeric material.

[0061] The placement of the functionalization material on the graphene is achieved with better bonding, and the functionalization material is deposited on clean graphene with good surface condition. The deposition of the functionalization material can minimize the mechanical stress on the graphene compared to other existing techniques.

[0062] The copper substrate 2 can be removed by chemical attack using iron(III) chloride or sodium persulfate, by oxidation of copper in hot water, or by electrochemical removal or formation of a gas film at the copper / graphene interface.

[0063] The graphene surface revealed by removal of the substrate is cleaned to remove contaminants, particularly those associated with copper etching.

[0064] Such a method has the advantage that large-scale devices can be fabricated by spraying the graphene removed from the growth furnace, i.e., the graphene at the end of step S1.

[0065] Following step S4, steps can be performed to complete the device, in particular subsequent integration steps such as the creation of electrical or electronic tracks for electrically connecting the graphene and / or the functionalization material to the connection terminals of the device.

[0066] <Roughness of the front surface of the graphene film> The polymeric materials used in this method, particularly parylene, allow for conformal deposition of functionalizing materials onto the graphene.

[0067] This allows the polymer material to encapsulate the functionalization material and the elements that compose it, even if these elements have a high degree of roughness, while preserving the initial flatness of the graphene on the initial growth substrate.

[0068] Surface roughness is defined in the present invention relative to a perfectly flat reference surface.

[0069] The reference plane includes mutually perpendicular directions X and Y (referred to as the lateral directions) and defines a third direction Z (referred to as the thickness direction) perpendicular to the plane.

[0070] In the vertical direction, the height (or altitude) z of the surface relative to a reference plane is defined.

[0071] This height z(x,y) is the average elevation of the surface relative to the reference plane in an area centred on a point with coordinates x,y on the reference plane, this area having lateral magnitude ΔX and magnitude ΔY in the lateral directions X,Y.

[0072] To quantify how a polymeric material allows for the encapsulation of the material and the elements that make up this material while maintaining the flatness of the graphene, the roughness of the graphene film (e.g., the front surface) is defined for an area that has a lateral size, i.e., lateral extent, that is greater than the average lateral extent of the elements that make up the functionalized material deposited on the graphene.

[0073] The average lateral extent of an element refers to the average size of the elements deposited on the graphene film, measured in the lateral directions X and Y.

[0074] The average element thickness refers to the average size of the elements deposited on the graphene film, measured in the thickness direction Z.

[0075] Furthermore, roughness is defined as the standard deviation of the distribution of front heights z as a function of position on the plane of the graphene film, this distribution being measured over an area with a lateral extent greater than that of the deposit.

[0076] For example, by defining roughness for a region having a size two or three times larger than the average range of elements, the increase in roughness with deposition of functionalizing material in this size range can be determined.

[0077] The method allows the flatness of the graphene to be maintained, so that the roughness of the front surface of the graphene film is less than the average thickness of the deposited elements compared to a surface without the deposited elements.

[0078] Preferably, this roughness is less than 10% of the average thickness of the deposition element, more preferably less than 1% of the average thickness of the deposition element.

[0079] For example, if the functionalization material consists of spherical beads, the surface roughness defined by the assembly of the rear surface of the graphene membrane and the functionalization material covering it, i.e., the “rear surface + functionalization material” assembly, increases by the value of the bead diameter for lateral samples larger than the bead diameter.

[0080] When the diameter of the beads is 4 μm, the surface roughness is about 4 μm.

[0081] The roughness of the front surface of the graphene obtained at the end of the method remains low and is significantly smaller than the roughness of the surface defined by the "back surface + functionalized material" assembly.

[0082] This is on the order of 1%, less than 5% and in any case always less than 10% of the thickness of the deposit.

[0083] Figure 6 illustrates this effect in a device obtained by the method described above, consisting of a graphene film 1, beads of functionalized material 3 and a polymer material 4.

[0084] The graphene membrane has a free front surface 1 a and a rear surface 1 b in contact with a functionalization material 3 and a polymer material 4 .

[0085] Roughness relates to the change in height, measured in the thickness direction Z, relative to a lateral area of ​​size, measured in the lateral direction X.

[0086] The bead 3 has a diameter T which corresponds to its thickness and lateral size.

[0087] T is the average size in all directions of the elements that make up the functionalizing material.

[0088] The deposition of the polymer material is conformal and the thickness of the layer of polymer material has a variation of thickness e1 at the location of the beads 3. This variation is equal to or comparable to the average size T.

[0089] The roughness of the front surface 1a is related to the variation in height e2 measured in the thickness direction Z relative to the lateral area of ​​the surface measured in the lateral direction X.

[0090] This change e2 is less than one tenth of the change in height e1, so that the flatness of the graphene is maintained throughout the method.

[0091] In comparison, in a method in which a functionalization material is deposited on a substrate so as to partially cover the substrate and then the substrate and functionalization material are covered with a graphene film (e.g., by liquid phase deposition), the graphene deposition is conformal, so that the roughness of the graphene film (e.g., the roughness of the free surface of the film) is comparable to the thickness of the object that constitutes the functionalization material.

[0092] Because the flatness of graphene is preserved, this method is extremely useful when the functionalized materials consist of objects with a "thickness / lateral size" aspect ratio of 1 or greater, particularly when these objects are spherical nanoparticles, nanocrystals, or nanotubes.

[0093] Maintaining the flatness of the graphene helps to avoid mechanical stress on the graphene film and thus the risk of it breaking.

[0094] The method allows for direct contact between graphene and functionalizing materials with a “thickness / lateral size” aspect ratio of 1 or greater, while eliminating the risk of tearing.

[0095] <Functionalized materials> Various types and forms of functionalization materials can be deposited on the rear surface of the graphene film.

[0096] In a first embodiment, the functionalization material is deposited in the form of metal nanowires.

[0097] These metal nanowires can be deposited, inter alia, on the graphene film by drop casting (referring to a method in which a solution is deposited on a flat surface followed by evaporation of the solvent from the solution to form a fine solid layer) or spin coating (referring to a method known to those skilled in the art in which a surface is coated by centrifugation of a viscous liquid).

[0098] Figure 2 shows a scanning micrograph of a device with a polymer (in this case parylene) layer and a graphene membrane. Between the parylene and graphene layers, silver nanowires 6 have been deposited by spin coating. The graphene layers are too small to be seen in the image, and the grey background 8 in the figure corresponds to the polymer layer holding the silver nanowires 6 and the graphene layer.

[0099] Silver nanowires were deposited on the graphene film by drop casting during step S2.

[0100] This device was fabricated according to the method described above using a copper substrate, which was removed in step S4.

[0101] The presence of silver nanowires can enhance the electrical conductivity of the graphene layers.

[0102] Such devices can be used, inter alia, in the manufacture of electrodes and conductive thin films.

[0103] In a second embodiment, the functionalization material is deposited in the form of semiconductor or metal nanowires or semiconductor quantum dots.

[0104] These metal nanowires can be deposited by drop casting, spin coating, simple dipping or spraying onto the graphene film, among others.

[0105] The presence of semiconductor nanowires or semiconductor quantum dots allows the conversion of light into electric charges. The light flux incident on the nanowires or quantum dots is converted into a flow of electric charges. These semiconductor nanowires or semiconductor quantum dots are encapsulated by graphene or parylene, which provides them with sufficient protection from environmental influences.

[0106] Such devices can be used in the manufacture of optical sensors, flexible optical sensors, and oxygen saturation detectors (commonly referred to as "SpO2" sensors), among others.

[0107] In a third embodiment, the functionalization material is deposited in the form of magnetic metal nanoparticles.

[0108] These magnetic metal nanoparticles can be deposited on the graphene film by drop casting or spin coating, among others.

[0109] The presence of magnetic metal nanoparticles allows for the generation of localized magnetic fields.

[0110] Such devices can be used, inter alia, for the manufacture of magnetic sensors and biosensors.

[0111] In such devices, the graphene-mediated long-distance effect (graphene does not block certain interactions, especially electromagnetic interactions) allows the interaction of the object to be characterized with the functionalization medium, which is a metal nanoparticle, placed in front of the graphene. The long-distance interaction with the object thus allows the selectivity of the sensor.

[0112] Also, instead of magnetic nanoparticles, a discontinuous ferromagnetic layer can be used.

[0113] It should be noted that graphene-mediated interactions can be measured by the graphene itself: for example, if the functionalization material consists of a nanomagnet inserted between the graphene and a polymeric material, magnetic particles present near the front surface of the graphene will be attracted towards the front surface, and this attractive force can be detected by the graphene.

[0114] In a fourth embodiment, the functionalization material is deposited in the form of an imaged thin metal film.

[0115] This printed metal film can in particular be deposited by physical vapour deposition (also known by the acronym PVD), for example by evaporation under vacuum, or by inkjet deposition of an ink onto the graphene film.

[0116] 3A, 3B, 3C, 3D are images illustrating different steps of an embodiment of the fourth aspect.

[0117] Figure 3A shows the inkjet deposition of silver ink, which corresponds to step S2 of the method of the fourth embodiment example. The deposition is performed on a graphene covering a copper substrate. The graphene is so fine that the copper is visible through it in Figure 3A.

[0118] FIG. 3B shows the graphene covering the copper substrate after inkjet writing is completed.

[0119] FIG. 3C shows step S4 of removing the copper substrate.

[0120] FIG. 3D shows the graphene-containing device after the step of removing the copper substrate.

[0121] The printed metal films make it possible to implement underlying interconnect structures on the graphene, such as a series of electrical or electronic circuits that connect the graphene layer to the rest of a larger device.

[0122] Such devices can be used, inter alia, to manufacture flexible printed circuits and embedded sensors, such as sensors located in the skin of plasmonic optical sensors.

[0123] In a fifth embodiment, the functionalization material is deposited in the form of a dielectric layer by atomic layer deposition (also called by the acronym ALD), which requires temperatures up to 200° C., limiting the variety of functionalization materials that can be deposited without damage.

[0124] Figure 4 shows a scanning micrograph of a device with a polymer (in this case parylene) layer and a graphene membrane, with a dielectric layer of alumina (Al2O3) deposited between them.

[0125] The thickness of the alumina dielectric layer is about 10 nm.

[0126] The graphene layers are too tiny to be seen in the image, allowing the alumina layers to show through.

[0127] This device was fabricated according to the method described above using a copper substrate, which was removed in step S4.

[0128] The presence of the dielectric layer allows for surface treatment of the graphene.

[0129] Such devices can be used to enhance the electronic performance of graphene in particular.

[0130] In a sixth embodiment, the functionalization material is deposited in the form of a boron nitride layer. This dielectric layer can be deposited by CVD.

[0131] The presence of the boron nitride layer allows an electrically insulating layer to be placed in contact with the graphene.

[0132] Such devices can be used to enhance the electronic performance of graphene in particular.

[0133] In a seventh embodiment, the functionalization material is deposited in the form of atoms, ions or molecules. For example, in the case of molecules, viologens can be deposited. These materials can be deposited by spin coating.

[0134] Figure 5 shows two scanning micrographs of a device with a polymer (in this case parylene) layer and a graphene film with viologen molecules deposited between them.

[0135] This device was fabricated according to the method described above using a copper substrate, which was removed in step S4.

[0136] The presence of viologen allows for n-doping of the graphene layers.

[0137] Such devices can be used in particular to fabricate electrical devices using n-doped regions based on the spatial organization between non-viologen doped graphene regions and viologen doped graphene regions.

[0138] In an eighth embodiment, the functionalization material is deposited by evaporation. The functionalization material can be deposited by condensation of a vapor or mist on the graphene film. The vapor contains volatile components and is pumped, for example from a liquid phase, through a vacuum chamber. The vapor recondenses on contact with the graphene film. A pulsed valve can be used to pump very small amounts of vapor onto the graphene film.

[0139] The vapor may contain multiple volatile components.

[0140] For example, the volatile component may be an acid or a base, an oxidizing or reducing agent, or a volatile organic compound.

[0141] This volatile component can act as a dopant or functional species for graphene.

[0142] At the end of the manufacturing process, the volatile components are located between the graphene and the polymer, and in particular are protected by the graphene layer from oxidation by elements such as oxygen located on the other side of the graphene, although this protection does not prevent the volatile components from interacting through the graphene with elements smaller than oxygen, such as hydrogen, located on the other side of the graphene.

[0143] The above-described methods can produce a graphene-comprising device that includes a graphene film partially covered by a functionalization material configured to modify a physicochemical property of the graphene film, and a polymeric material covering the graphene film and the functionalization material such that the polymeric material contacts at least a portion of the graphene film that is not covered by the functionalization material.

[0144] The present invention therefore further relates to a device in which the front side of the graphene film exhibits surface conditions not obtainable with existing techniques in the prior art.

[0145] In particular, the present invention relates to devices in which the polymeric material is parylene.

[0146] The method also enables the fabrication of flexible field-effect transistors with graphene-containing channels, where the sensitive region of such a transistor may correspond to a break in the ribbon of functionalizing material that separates the graphene and the polymer.

Claims

1. A method of forming a device (5) comprising graphene, comprising: Step S1 of forming a graphene film (1) on a substrate (2); a step S2 of depositing on the graphene film (1) a functionalization material (3) configured to modify the physicochemical properties of the graphene film (1), the deposition of the functionalization material being configured to partially cover the graphene film (1) such that at least a portion of the graphene film (1) is not covered by the functionalization material; a step S3 of vapor-depositing a polymer material (4) covering the graphene film (1) and the functionalization material (3) so that the polymer material (4) contacts at least the portion of the graphene film (1) that is not covered by the functionalization material; a step S4 of removing the substrate (2) so that the polymer material (4) forms a support for the graphene film (1); A method comprising:

2. The functionalization material (3) is deposited on the graphene film (1) during step S2 in the form of elements having an average thickness perpendicular to the graphene film (1) and an average lateral extent in a plane parallel to the graphene film, the graphene film has a front surface and a rear surface opposite the front surface at the end of step S4 of removing the substrate; the rear surface is in contact with the functionalized material and the polymeric material; said front surface being a free surface and having a roughness less than said average thickness of said elements of said functionalization material (3); 2. The method of claim 1, wherein the roughness is determined relative to a flat surface, the roughness being equal to the standard deviation of the front surface height in the vertical direction as a function of position in the plane of the graphene film, the front surface height being defined relative to an area in the plane that is greater in size than the average lateral extent.

3. 3. The method of claim 2, wherein the roughness relative to a reference surface is less than 10% of the average thickness, preferably less than 5% of the average thickness.

4. The method according to any one of claims 1 to 3, wherein the polymer material (4) comprises parylene.

5. 4. The method according to any one of claims 1 to 3, wherein the functionalization material (3) is deposited in the form of at least one of metal nanowires, semiconductor nanowires or semiconductor quantum dots, magnetic metal nanoparticles, patterned metal thin films, dielectric layers deposited by atomic layer deposition (ALD), boron nitride layers deposited by chemical vapor deposition (CVD).

6. A device (5) comprising graphene, a graphene film (1) partially covered with a functionalization material (3) configured to modify the electrical or magnetic properties of the graphene film (1); a polymer material (4) covering the graphene film (1) and the functionalization material (3) such that the polymer material (4) is in contact with at least a portion of the graphene film (1) that is not covered by the functionalization material; Devices containing:

7. the functionalizing material (3) is composed of elements having an average thickness perpendicular to the graphene film (1) and an average lateral extent in a plane parallel to the graphene film, the graphene film has a front surface and a rear surface opposite the front surface; the rear surface is in contact with the functionalized material and the polymeric material; said front surface being a free surface and having a roughness less than said average thickness of said elements of said functionalization material (3); 7. The device of claim 6, wherein the roughness is determined relative to a flat surface, the roughness being equal to the standard deviation of the front surface height in the vertical direction as a function of position in the plane of the graphene film, the front surface height being defined relative to an area in the plane that is greater in size than the average lateral extent.

8. 8. A device according to claim 6 or 7, wherein the roughness relative to a reference surface is less than 10% of the average thickness, preferably less than 5% of the average thickness.

9. 8. The device according to claim 6 or 7, wherein the polymer material (4) comprises parylene.

10. 8. The device according to claim 6 or 7, wherein the functionalization material (3) is deposited in the form of at least one of metal nanowires, semiconductor nanowires or semiconductor quantum dots, magnetic metal nanoparticles, patterned metal thin films, dielectric layers deposited by atomic layer deposition (ALD), boron nitride layers deposited by chemical vapor deposition (CVD).

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