Scalable production of graphene structures

Abstract

The invention relates to a graphene structure, a graphene-based device and a manufacturing method thereof. A graphene structure detachably disposed and formed on a substrate includes a graphene layer formed on the substrate. In addition, the graphene structure includes a first patterned structure extending over a first side of a graphene layer formed on the substrate. The graphene structure further includes a capping layer attached over the first patterned structure and the graphene layer.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to stacked graphene structures and methods of forming such graphene structures. In particular, embodiments and aspects of the present disclosure relate to graphene-based devices comprising stacked graphene structures and applications thereof. BACKGROUND

[0002] Graphene has been a very promising two-dimensional (2D) material in the field of electronics and optoelectronics since its discovery. The flexibility, transparency and excellent electrical conductivity of graphene paved the way for advancements in several scientific fields, such as flexible electronic devices, sensor devices and transistor devices. The excellent mechanical properties of graphene have attracted great interest for use in stretchable electronic devices. In addition, graphene has ideal properties such as high chemical stability, wide optical absorption spectrum, excellent transparency and electrical sensitivity to biochemical substances, making it a promising material for displays, light harvesting devices and biosensors.

[0003] It has been found that chemical vapor deposition (CVD) of graphene on copper foils provides a scalable method to obtain high quality single layer graphene, which can then be used for further processing and intended applications. High quality graphene refers to a material that is free of contamination, wrinkles, cracks or any other defects, characterized by its single crystalline nature.

[0004] However, subsequent applications often require the transfer of graphene onto different substrates. A widely used method involves depositing a sacrificial polymer layer on the grown graphene layer, followed by removal of the copper substrate and dissolution of the polymer layer. Unfortunately, this process is cumbersome and often results in contamination of the graphene surface by polymer residues. Contamination leads to deterioration of the electrical properties of graphene, in particular to a reduction of the carrier mobility of the transferred graphene compared to exfoliated graphene. Despite ongoing efforts, large scale production of high quality graphene devices using scalable and cost-effective methods remains a challenge and there is a need in the field of graphene production as well as in the field of graphene-based devices to develop a general solution that addresses some of the above-mentioned shortcomings. SUMMARY

[0005] It is therefore an object of the present invention to improve the state of the art and to alleviate at least some of the above-mentioned problems.

[0006] These and other objects are achieved by providing a method of forming a stacked graphene structure as defined in the appended independent claims and dependent claims, the formed stacked graphene structure and a graphene-based device manufactured by the proposed method. The term exemplary is to be understood in the context of the present document as used by way of example, illustration or description.

[0007] According to a first aspect of the present disclosure, there is provided a method of manufacturing a stacked graphene structure. The method comprises forming a graphene layer on a substrate, and forming a first patterned structure extending over a first side of the graphene layer formed on the substrate. The method further comprises forming a cover layer over the first patterned structure by attaching the cover layer on the first patterned structure and the graphene layer formed on the substrate; wherein the stacked graphene structure comprises at least the graphene layer, the first patterned structure and the attached cover layer.

[0008] In various exemplary embodiments, the method can further comprise forming the first patterned structure by depositing the first patterned structure on top of the first side of the graphene layer formed on the substrate. Additionally or alternatively, the method can comprise forming the first patterned structure by depositing the first patterned structure on one or more edge portions of the graphene layer.

[0009] According to several embodiments, the method can further comprise attaching the cover layer on top of the first side of the first patterned structure and on top of the first side of the graphene layer formed on the substrate. More specifically, the method can comprise attaching the cover layer in physical contact with the first side of the first patterned structure by gluing the cover layer on top of the first side of the first patterned structure and the first side of the graphene layer. The method can further comprise providing permanent attachment of the cover layer on top of the first side of the first patterned structure and the first side of the graphene layer.

[0010] According to several embodiments, the method can further comprise forming a second layer stack between the graphene layer formed on the substrate and the first patterned structure by depositing a second layer stack on top of the first side of the graphene layer formed on the substrate. The method can further comprise forming the first patterned structure on top of the first side of the deposited second layer stack; wherein the stacked graphene structure can further comprise the second layer stack.

[0011] In several embodiments, the method can further comprise attaching the cover layer on top of the first side of the first patterned structure and the first side of the deposited second layer stack. More specifically, the method can comprise attaching the cover layer in physical contact with the first side of the first patterned structure and the first side of the deposited second layer stack by gluing the cover layer on top of the first side of the first patterned structure and the first side of the deposited second layer stack. Accordingly, the method can further comprise providing permanent attachment of the cover layer on top of the first side of the first patterned structure and the first side of the deposited second layer stack.

[0012] In several embodiments, the first patterned structure can comprise a conductive material or a conductive ink, the conductive material comprising a metal, and the first patterned structure can be adapted to function as a conductive electrode. In some embodiments, the first patterned structure can be made entirely of a conductive material.

[0013] In several embodiments, the second layer stack can be made of a dielectric material.

[0014] In several embodiments, the cover layer can comprise an insulating material. The insulating material can comprise any of a plastic, a glass, or a sapphire.

[0015] In several embodiments, the method can further comprise separating the stacked graphene structure from the substrate by detaching the stacked graphene structure, such that a second side of the graphene layer opposite the first side of the graphene layer can be exposed.

[0016] In several embodiments, the method can further comprise detaching the stacked graphene structure from the substrate by any of an electrochemical exfoliation method, a mechanical exfoliation method, or an etching process.

[0017] In several embodiments, the method can further comprise forming a third layer stack by depositing a third layer stack on top of the exposed second side of the graphene layer separated from the substrate. Additionally or alternatively, the method can comprise forming a second patterned structure extending over the second side of the graphene layer. Thus, the inventors have realized that the graphene layer can be subjected to several manufacturing steps, resulting in a manufacturing stack of several hundred nanometers on top of the graphene layer, which can comprise the first patterned structure and the second layer stack (e.g., a dielectric layer). Interestingly, the graphene retains its electrical and physical properties when the graphene layer and the patterned structures manufactured on the graphene layer according to the embodiments herein are released from the substrate, under the support of the cover layer.

[0018] According to a second aspect of the present disclosure, there is provided a graphene structure detachably arranged and formed on a substrate, wherein the graphene structure comprises a graphene layer formed on the substrate. The graphene structure further comprises: a first patterned structure extending over a first side of the graphene layer formed on the substrate; and a cover layer attached on the first patterned structure and the graphene layer.

[0019] In several embodiments, the graphene structure can further comprise a second layer stack arranged between the graphene layer and the first patterned structure, the second layer stack deposited on top of the first side of the graphene layer; wherein the first patterned structure can be arranged on top of a first side of the deposited second layer stack.

[0020] According to a third aspect of the present disclosure, there is provided a graphene-based sensor device or a graphene field effect transistor device comprising a stacked graphene structure manufactured by the method of any one of the embodiments of the method according to the first aspect of the present disclosure.

[0021] According to a fourth aspect of the present disclosure, there is provided a graphene field effect transistor device formed of or comprising a stacked graphene-based structure according to any one of the embodiments of the method according to the first aspect of the present disclosure or any one of the embodiments of the graphene structure according to the second aspect of the present disclosure. The transistor device comprises a graphene layer having a first side and a second side opposite the first side. The transistor device further comprises a gate dielectric layer stack arranged at the first side of the graphene layer. The transistor device further comprises a first patterned gate electrode arranged at the first side of the gate dielectric layer stack. The transistor device further comprises a cover layer attached on the first patterned gate electrode and the first side of the gate dielectric layer stack. The attached cover layer is configured to enclose the first patterned gate electrode and further support the first patterned gate electrode, the gate dielectric layer stack and the graphene layer. The transistor device further comprises a second patterned electrode structure comprising a first source electrode portion and a second drain electrode portion arranged at opposite ends of the graphene layer; wherein the second side of the graphene layer is exposed.

[0022] In several embodiments, the transistor device can further comprise a cover dielectric layer arranged at the second side of the graphene layer and configured to cover the exposed second side of the graphene layer.

[0023] According to a fifth aspect of the present disclosure, there is provided a method of manufacturing a stacked graphene structure, the method comprising: forming a first patterned structure extending over a first side of a cover layer configured to support the first patterned structure. The method comprises: forming a pre-patterned cover layer, wherein the first patterned structure is made of an electrically conductive material. The method further comprises: attaching the pre-patterned cover layer on a graphene layer formed on a copper foil substrate, wherein the stacked graphene structure comprises at least the graphene layer and the attached pre-patterned cover layer.

[0024] In several embodiments, the method of the fifth aspect can further comprise: attaching the pre-patterned cover layer by gluing the pre-patterned cover layer on top of the first side of the graphene layer. In this way, the first side of the patterned electrode structure and the first surface of the cover layer are arranged in physical contact with the first side of the graphene layer. The method can thus further comprise: providing a permanent attachment of the pre-patterned cover layer on top of the first side of the graphene layer.

[0025] According to a sixth aspect of the present disclosure, there is provided a stacked graphene structure, which is detachably arranged and formed on a copper foil substrate. The graphene structure comprises a graphene layer formed on the copper foil substrate. The graphene structure comprises a pre-patterned cover layer permanently attached on top of a first side of the graphene layer, wherein the pre-patterned cover layer comprises a first patterned structure made of an electrically conductive material and extending over the first side of the pre-patterned cover layer configured to support the first patterned structure.

[0026] Other features and advantages of the present application will become apparent from the accompanying claims and the following description. Those skilled in the art will recognize that the various features of the present disclosure can be combined in different ways without departing from the scope of the present disclosure.

[0027] Further embodiments are defined in the dependent claims.

[0028] It is noted that all embodiments, elements, features and advantages associated with the first aspect are likewise applicable analogously to the second aspect, the third aspect, the fourth aspect, the fifth aspect and the sixth aspect of the present disclosure.

[0029] These and other features and advantages of the present disclosure will be further clarified by the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0030] Further objects, features and advantages of embodiments of the present disclosure will appear from the following detailed description, with reference to the drawings. The drawings are not to scale.

[0031] Figure 1 a to Figure 1 Figures a to g show schematic cross-sectional side view illustrations of a stacked graphene structure according to several embodiments of the present disclosure.

[0032] Figure 2 a to Figure 2 Figures a to e show schematic cross-sectional side view illustrations of another stacked graphene structure according to several embodiments of the present disclosure.

[0033] Figure 3 a to Figure 3 Figures a to g show schematic cross-sectional side view illustrations of yet another stacked graphene structure according to several embodiments of the present disclosure.

[0034] Figure 4 a to Figure 4 Figures a to d show schematic cross-sectional side view illustrations of still another stacked graphene structure according to several embodiments of the present disclosure.

[0035] Figure 5A flowchart illustrating a method in accordance with several embodiments of the present disclosure is shown.

[0036] Figure 6 A flowchart illustrating a method in accordance with several embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0037] In the detailed description that follows, embodiments of the present disclosure are discussed with reference to the figures. In the description of the example embodiments below, like parts are marked throughout the figures with the same references numbers. It should be noted that those skilled in the art will understand that the present application can be practiced with the elements or features not specifically described herein but with any other type or variation of elements or features.

[0038] The following description can use terms such as "top," "bottom," "upper," "inner," "outer," "side," "edge," "ridge," "distal," "proximal," "front," "back," etc. Different components, layers, and structures herein can be described as having one or more sides, each of which can be considered to have a respective surface. These terms are generally made with reference to the views and orientations as shown in the drawings. These terms are used only to facilitate the reader's understanding of the present application and should not be construed to limit.

[0039] In the context of the present application, directions and orientations (e.g., vertical, horizontal, longitudinal, and transverse directions, as well as extensions) are to be interpreted broadly and generally refer to the geometric extension of an object in a coordinate system (e.g., a three-dimensional Cartesian coordinate system). The spatial extension and position of an object can be defined in at least one plane of the coordinate system (e.g., by using x, y, z coordinates and their corresponding angles).

[0040] It should also be understood that the terms used herein are for the purpose of describing particular embodiments and are not intended to be limiting. It should be noted that, as used in the specification and the appended claims, the articles "a," "an," "the," and "said” are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" can mean more than one unit, and the like. Furthermore, the words "comprise,” "comprises,” "comprising,” "include,” "includes,” and "including” are not used

[0041] In this context, and for the purposes of the proposed solutions, methods, implementations, and processes, the term “forming” encompasses any suitable fabrication and material deposition technique in the field of producing graphene structures and devices according to various aspects and embodiments of this document.

[0042] It will also be understood that although the terms first, second, etc., may be used herein to describe various elements or features, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0043] The various aspects of this disclosure will be described below in conjunction with the accompanying drawings to illustrate, rather than limit, the disclosure, wherein like reference numerals denote like elements, and variations of the described aspects are not limited to the embodiments specifically shown, but can be applied to other variations of the disclosure.

[0044] As previously mentioned, significant progress has been made in the synthesis of graphene, particularly through methods such as chemical vapor deposition (CVD), enabling the production of graphene films with robust structural integrity on transition metal substrates (typically copper). However, many graphene-related technologies require specific substrates, such as semiconductors and metal oxides. Therefore, additional processes are often needed to transfer CVD graphene onto the desired technology substrate. Achieving this transfer process while preserving the original properties of graphene requires meticulous care and precise process control. Preventing the introduction of any defects during the transfer process is crucial, emphasizing the need for rigorous attention to detail and adherence to best practices. The methods and devices presented in this paper offer a simpler and more sustainable fabrication approach for realizing high-quality graphene devices.

[0045] Figure 1 a to Figure 1 Figure d shows a schematic cross-sectional side view of a stacked graphene structure 1 according to several embodiments and aspects herein. The term "stacked" as used herein is to clarify that in various embodiments, the graphene structure may have several layers of material arranged on top of and / or on top of each other. For simplicity only, throughout the remainder of this specification, the stacked graphene structure 1 may be interchangeably referred to as graphene structure 1 or component 1. The figures illustrate several layers and their arrangements in the graphene structures and devices presented herein; however, the dimensions, extensions, and thicknesses of the layers depicted are not to scale and should not be construed as limiting.

[0046] As previously stated, the graphene structure 1 proposed herein can be fabricated using any method and manufacturing process, such as, but not limited to, material deposition methods known in the art via evaporation, CVD, or sputtering; wet or dry etching of materials; and patterning techniques using photolithography, electron beam lithography, nanoprinting lithography, or inkjet printing. The graphene structure 1 can be detachably, or removably, arranged and formed on the substrate 200. Figure 1(a) is shown, the graphene layer 11 is arranged on a top surface 200a of the substrate 200, with the second side 11b (bottom side 11b) of the graphene layer 11 in physical contact with the top surface 200a of the substrate 200. Figure 1 The first side 11a (top side 11a) of the graphene layer 11 in a is exposed. The extension and orientation of the substrate 200, the graphene layer 11 and other components of the graphene structure (e.g., the top or bottom side in Figures 1 to 4 a) is explained with respect to a Cartesian coordinate system as shown in Figure 1 These terms are only used for the convenience of the reader and shall not constitute a limitation. For example, the longest extension of the substrate 200 and the graphene layer 11 arranged thereon is shown to be in the x-direction. The graphene layer 11 is deposited on a surface 200a of the substrate 200 which extends in parallel to the longest direction. In some other examples, the longest extension of the substrate 200 can be in the y-direction. In the context herein, the term detachably or removably is to be understood that the graphene structure is manufactured, patterned and otherwise functionally prepared on the substrate 200. However, the graphene layer and the stacked structure manufactured on the graphene layer are adapted to be detached from the substrate as required. In other words, the functional components for forming the graphene structure or a graphene-based device comprising the graphene structure are all or partially manufactured on the substrate 200. The manufactured graphene structure 1 can then be removed or detached by the methods presented herein for the intended exemplary applications. In use, the graphene structure 1 or an exemplary graphene device comprising any of the various graphene structures 1 presented herein is in a detached state from the substrate 200. However, the graphene structure 1 presented herein can be manufactured and stored for later use while the graphene structure 1 is still arranged on the substrate 200. The detachment step according to several aspects and embodiments herein can ensure that the graphene structure 1 is used for the intended applications or for further processing and subsequent post-detachment manufacturing steps. In several embodiments, the substrate 200 can be a metal substrate. More specifically, the metal substrate 200 can be a metal foil, which can be a copper foil 200. In some embodiments, the metal substrate 200 can be a metal plate or block. When reference is made to the “substrate 200” in the present disclosure, it is to be understood that any of the above suitable alternatives can be utilized. The use of a copper foil as the substrate 200 according to various embodiments herein provides the advantage that the problem of depositing a thin film of metal on a solid substrate (such as Si / SiO2) using cumbersome physical vapor deposition methods (such as thermal or e-beam evaporation, sputtering, etc.) is alleviated. Furthermore, the use of a copper foil substrate makes the manufacturing process more cost-effective and time-efficient.

[0047] In Figure 1 a, a graphene layer 11 is formed (e.g., by a CVD deposition method) on the substrate 200. In Figure 1 b1 and Figure 1In b2, a first patterned structure 12 is formed extending above the first side 11a of the graphene layer formed on the substrate 200. Figure 1 In an alternative to b1, the first patterned structure 12 may be formed over the graphene layer 11, such that the first patterned structure 12 is in physical and electrical contact with the top surface or first side 11a of the graphene layer 11. In other words, the first patterned structure 12 is deposited on top of the first side 11a of the graphene layer 11. The patterned structure 12 may be deposited on top of the first surface 11a. In several embodiments, the first patterned structure 12 may be made of a conductive material, including metal, or conductive ink. The first patterned structure may be adapted to serve as a conductive electrode. The contact 12 deposited on the top surface 11a of the graphene layer 11, in physical and electrical contact with the graphene layer 11, may also be referred to herein as a top contact arrangement. However, in several embodiments, the first patterned structure 12 may be deposited on one or more edge portions 11c, 11d of the graphene layer 11. In other words, as exemplarily Figure 1 b2 and Figure 1 As shown in d2, the first patterned structure 12 may include edge contacts that are electrically and physically connected to the edge portions 11c and 11d of the graphene layer 11.

[0048] In any of the above alternatives, the stacking direction of the first patterned structure 12 is substantially perpendicular to the graphene layer 11. The first patterned structure 12 and the graphene layer 11 have... Figures 1 to 4 The example shows the corresponding height profile extending in the z-direction (representing the corresponding thicknesses of the first patterned structure 12 and the graphene layer 11). The z-direction corresponds to the stacking direction of the first patterned structure 12, the second layer stack 14, and the capping layer 13 when they are arranged on the substrate 200. In this context, when it is mentioned that the first patterned structure extends above the first side of the graphene layer, it should be understood that the height of the first patterned structure 12 extends beyond the height of the formed graphene layer 11. In other words, the first side 12a (top side 12a) of the first patterned structure 12 has a greater height relative to the top surface 200a of the substrate 200 than the first side 11a (top side 11a) of the graphene layer. Furthermore, as mentioned above regarding... Figure 1 b1 and Figure 1 The alternative to b2 explains that the first patterned structure extending above the first side of the graphene layer will be in physical and electrical contact with the graphene layer and / or the substrate.

[0049] The first patterned structure 12 can be formed by an etching or lift-off fabrication process. For example, a sacrificial photoresist layer (not shown) having the intended pattern of the first patterned structure can be applied on the first side 11a of the graphene layer 11, and a first layer stack (not specifically shown) for forming the first patterned structure can be deposited on the sacrificial layer. After a lift-off process, the remnants of the first layer stack that are not part of the intended pattern are removed, leaving the first patterned structure 12. Alternatively, the first layer stack (not specifically shown) can be deposited on the first side 11a of the graphene layer 11 and then etched away by chemical wet etching, leaving the first patterned structure 12. The above exemplary methods as well as other fabrication methods can be used to form various patterned structures according to the present disclosure.

[0050] In various embodiments, the graphene structure 1 further comprises a cover layer 13 or alternatively referred to herein as a cladding layer 13 or support layer 13. The cover layer 13 is formed over the first patterned structure 12 and the graphene layer 11 by attaching the cover layer 13 on the first patterned structure 12 and the graphene layer 11. In the present context, “attached on” means that the cover layer 13 is on top of and in direct physical contact with the first patterned layer 12 and the graphene layer 11, or that the cover layer 13 is attached to an intermediate layer (e.g. layer 14) arranged on the graphene layer 11, see Figure 2 a to Figure 2 e. In any case, the cover layer 13 at least partially surrounds and covers the layer or layers below the cover layer 13. In several embodiments, the cover layer 13 can completely cover the top surface of the layer or layers on which the cover layer 13 is deposited, e.g. the first side 11a of the graphene layer 11 and the entire surface of the first patterned layer 12 in Figure 1 a to Figure 1 d. In several embodiments, the cover layer 13 can be attached to the graphene layer and the first patterned layer by means of gluing the cover layer 13. Gluing can be performed by using an adhesive material. Thus, the gluing process in the present context should be understood as permanently attaching the cover layer to the layers below the cover layer by means of a gluing layer 113 or adhesive material. In several embodiments and for

[0051] In several embodiments herein, the cover layer can be made of an insulating material including any of a plastic, a thermoplastic, a glass, a sapphire or other dielectric material. The plastic can include different suitable types of plastic, such as PET / EVA (polyethylene terephthalate / ethylene-vinyl acetate). In several aspects and embodiments, the cover layer 13 can be attached to the graphene layer and the first patterned layer by means of gluing the cover layer 13. Gluing can be performed by using an adhesive material. Thus, the gluing process in the present context should be understood as permanently attaching the cover layer to the layers below the cover layer by means of a gluing layer 113 or adhesive material. In several embodiments and for Figures 1 to 4The adhesive layer 113 is configured to conform to the topography of the underlying layers in the illustrated device. In several embodiments, a separate layer of adhesive 113 can be applied to the underlying layers, and the insulating portion 114 of the cover layer 13 is disposed on top of the adhesive layer 113. However, in several embodiments, the cover layer 13 can include an integrated adhesive layer 13-1 (i.e., an adhesive layer that acts as an adhesive). For example, as illustrated in Figure 1 g, in several embodiments, the cover layer 13 can include a bi-layer structure, for example, a PET / EVA combination. The EVA sub-layer 13-1 will act as an adhesive layer that permanently attaches the top insulating PET sub-layer 13-2 to the underlying graphene layer 11 and first patterned layer 12. In some embodiments, the adhesive layer can be an epoxy or a cyanoacrylate (super glue), while the top sub-layer can be any other polymer, glass, or Si wafer. Thus, the adhesive layer 113, 13-1 will conform to the boundaries and topography of the underlying surface, for example, as illustrated in Figure 1 g for the PET / EVA combination. In some embodiments, the insulating portion 114 of the cover layer 13 can be made of a rigid material, for example, glass 114. The rigid insulating portion 114 will adhere to the underlying adhesive layer 113 that conforms to the topography of the underlying surface, as illustrated in Figure 1 f. Unless otherwise specified, in the context of this document and in the remainder of this specification, when referring to the cover layer 13, the cover layer 13 includes the adhesive layer 113, 13-1 and the insulating layer 114, 13-2 that is attached to the underlying surface by the adhesive layer 113, 13-1. Thus, even if not specifically illustrated, for example, in Figure 1 c1, exemplary arrangements of the insulating layer 114, 13-2 and adhesive layer 113, 13-1 are intended to have been applied and are present in Figures 1 to 4 the illustrated several embodiments.

[0052] The gluing can include laminating the cover layer 13. In some embodiments, the gluing can include partially melting the cover layer 13 by heating to cause the cover layer 13 to adhere to the underlying surface. In several exemplary embodiments, the lamination is achieved by using a polymeric adhesive, assisted by a standard hot roll lamination process. This step involves laminating the prepared graphene stack 1 to the cover layer 13 by a laminator.

[0053] In several embodiments, the cover layer can be attached on top of the first side 12a of the first patterned structure 12 and the first side 11a of the graphene layer formed on the substrate 200, as illustrated in Figure 1 c1, Figure 1 d1, Figure 1 c2and Figure 1d2. The adhesive cover layer 13 provides permanent attachment of the cover layer 13 to the surface on which the cover layer 13 is adhered. The first surface 13a (may alternatively be referred to as the first side 13a or bottom side 13a) of the permanently adhered cover layer 13 is arranged in physical contact with the surface to which the cover layer 13 is adhered. It should be clear to the skilled person that the bottom side 13a of the cover layer 13 can be the bottom surface 13a of the adhesive layer 113, 13-1 of the cover layer 13 in physical contact with the underlying surface, as Figure 1 f、 Figure 1 g.

[0054] Furthermore, it should be clear to the skilled person that when referring throughout the specification to a first component (e.g. the cover layer 13) being attached on top of a second component (e.g. the first side 12a of the first patterned structure 12), the term "on top of" is merely used for the convenience of the reader and should not be construed as limiting. It is equally conceivable that if Figure 1 c1、 Figure 1 d1、 Figure 1 c2and Figure 1 the vertical orientation of the exemplary device 1 in

[0055] In the present context, permanent attachment refers to an attachment that is irreversible and durable. The advantage provided in this way is that the cover layer 13 is used as the final support substrate 13 and forms the base of the device on which the entire device 1, 110, 120, 130 will rest, e.g. after being separated from the copper substrate 200 and during use and operation of the device 1, 110, 120, 130. More specifically, the second surface 13b (may alternatively be referred to as the second side 13b or top side 13b) of the cover layer 13 will act as the base of the final device 1, 110, 120, 130 having the bottom surface 13b.

[0056] In some exemplary embodiments, the graphene structure 1 or assembly 1 can be manufactured by forming a graphene layer or film 11 on a substrate 200. Furthermore, the electrical contacts 12 (first patterned structure) can be manufactured to be electrically connected with the graphene film 11, as Figure 1 a to Figure 1d. The assembly can be formed by gluing the support substrate 13 or the cover layer 13 to the graphene film 11 formed on the substrate 200. The substrate 200 (e.g. the metal foil 200) is removed (i.e. detached) from the assembly, thereby revealing the graphene film 11 at the bottom 1 lb of the assembly 1. Thus, a multilayer assembly 1 can be provided, which comprises at least the graphene film 11, the electrical contacts 12 to the graphene film 11 and the support substrate 13 glued to the graphene film 11. In several embodiments, the cover layer 13 can be a flexible support substrate configured to support the graphene structure 1. Thus, the advantages of manufacturing flexible graphene-based devices having various applications in the field of flexible electronics are achieved. Several graphene-based devices, such as sensor devices (biosensors), transistor devices (e.g. field effect transistors (FETs)), medical devices such as electrical stimulation devices for wound healing, etc. can be manufactured by the method and the graphene structure 1 presented herein. Thus, the devices advantageously can comprise various graphene structures 1 as explained herein suitable for their intended applications.

[0057] As previously mentioned, the two-dimensional structure of graphene has several benefits compared to bulk-type semiconductors (e.g. silicon) used in standard FETs. A FET is an electronic component that uses an electric field in its vicinity and its associated voltage difference to regulate the flow of electric current. A FET is typically a device with three terminals or electrodes: a semiconductor channel runs between two of these electrodes (the source and the drain), while the third electrode (called the gate) acts as a control. The voltage difference applied to the gate allows or prevents the transport of electric charges through the semiconductor channel depending on its direction and intensity. A graphene field effect transistor (GFET) adopts the typical FET device structure and inserts a graphene channel between the source and the drain. As graphene (only one atomic lattice of carbon atoms thick), the channel in a GFET has a high sensitivity to external stimuli, which can be used for a wide variety of applications (e.g. optical, magnetic and biosensing). Since most semiconductor transistor sensors are three-dimensional, changes in the charge at the surface of the channel do not always penetrate deep into the device. This limits the sensitivity of conventional devices. On the other hand, since graphene in a GFET is only one carbon atom thick, the entire channel is now a surface, which exposes the entire channel to any molecules present in the immediate environment. This is for example in a sensor device 110 in e, which will be further explained below. In this example, the graphene-based device 110 can be a GFET device 110 or a graphene-based sensor device 110, whose second side 1 lb of the graphene layer 11 is revealed, which can be brought into the immediate vicinity of e.g. a cell culture or a tissue in which a large number of molecules are present. Figure 2

[0058] ​Current diagnostic tools face numerous challenges in meeting the clinical requirements of speed, throughput, accuracy, cost, and ease of use. GFETs prepared according to embodiments herein are expected to be used in a variety of applications in the biomedical field and the like. For example, by the proposed graphene-based devices functionalized with receptors that capture infectious biomarkers, an infectious diagnostic kit can be developed. Such devices can be used as plug-and-play disposable chips with micro-SD jacks to simplify the contact of the chip. Miniaturized, low-cost, fast, high-sensitivity, and specific graphene-based sensors including graphene structure 1 can be developed for the detection of bacterial infections in hospital environments. These devices will be suitable for the detection and subspecies-level classification of infectious bacteria, particularly high virulence strains. The aforementioned devices can also be prepared to be incorporated into biomedical devices (e.g., catheters, implants), allowing for the timely replacement of the device in case of bacterial attachment.

[0059] By utilizing the proposed graphene structure 1 in biosensors, more economical and reliable devices for the detection of harmful bacteria and viruses can be produced. This also includes the detection of bacteria or fungi in food and the detection of food spoilage, thereby helping to use food more efficiently while avoiding food poisoning. In addition to biosensing, the prepared GFETs have great prospects in the field of low-cost electronics for future terahertz frequency-based high-speed wireless communication and non-invasive inspection. Graphene, with its unique combination of flexibility and high carrier mobility, can offer new opportunities for terahertz electronics. The power sensors based on graphene structure 1 herein can be used as fast and sensitive detectors within a wide portion of the electromagnetic spectrum. Graphene seems ideally suited as a sensing material in Hall effect sensors due to its very high mobility and low charge carrier density, as well as its mechanical flexibility. Fabricating graphene-based Hall sensors based on graphene structure 1 herein is expected to be superior to silicon and other rigid sensors based on III / V semiconductors. This is an additional advantage because graphene-based Hall sensors are significantly superior to all other technologies on flexible substrates. Magnetic field sensors are widely used in several key industries, such as consumer electronics, automotive, healthcare, and robotics, where they provide position and speed detection, switching applications, or current monitoring. By providing efficient, flexible, and scalable graphene structure 1 and methods of fabricating the same according to the present disclosure, a significant more efficient use of a large amount of time and resources can be used. Still further, electrical stimulation systems and devices for applications such as tissue stimulation, wound healing, and the like can be designed based on graphene structure 1 herein. For example, Figure 2 device 110 of e or Figure 1 d1 and Figure 1The device 110 with graphene structure 1 in d2 can interface with a biological environment (e.g. a tissue portion) using the exposed portion 1 1 b of graphene and the electrodes 12. Thus, the device can be used to read electrical or electrochemical signals from the tissue and its surrounding environment, operate as a biosensor, and transmit a stimulating electrical signal to the tissue. The excellent transparency of the graphene layer in graphene structure 1 will also allow these devices to be combined with laser-based technologies.

[0060] In the context herein, where it is mentioned that a first layer or structure is on top of another layer or structure (i.e. a second layer or structure), it is to be understood that the first layer has physical and / or electrical contact on top of the second layer, or alternatively, there can be one or more intermediate layers between the first and second layers.

[0061] For example, as shown in Figure 2 a to Figure 2 e, the first patterned structure 12 can be arranged on top of the graphene layer 1 1 without having any physical or electrical connection with the graphene layer 1 1. In this example, the second layer stack 14 (i.e. the intermediate layer 14) is arranged between the graphene layer 1 1 formed on the substrate 200 and the first patterned structure 12 by depositing the second layer stack 14 on top of the first side 1 1 a of the graphene layer 1 1 formed on the substrate. Thus, the first patterned structure 12 can be deposited on top of the first side 14a of the deposited second layer stack 14, i.e. in physical contact with the second layer stack 14, but not in physical contact with the graphene layer 1 1. The cover layer 13 can thus be attached on top of the first patterned structure 12, i.e. in physical contact with the first side 12a of the first patterned structure 12 and the first side 14a of the deposited second layer stack 14. In several embodiments and aspects, the second layer stack can be made of a dielectric material. In several embodiments, the dielectric material can be any suitable dielectric material. More specifically, in some examples, the dielectric material 14 can be a Parylene N dielectric layer. The inventors have recognized that the use of Parylene N has several advantages, i.e. Parylene N acts as a clean substrate for graphene and can be deposited at room temperature by a direct CVD deposition method. Furthermore, Parylene N is flexible, cost-effective, and can be manufactured in a scalable deposition process. Parylene N also has a high breakdown voltage and has a similar dielectric constant as Si02. Unlike other dielectrics (ALD Al203, Hf02), Parylene N does not require a seed layer.

[0062] In 4a to Figure 4 In another example embodiment shown in 4a to d, the first patterned structure 15a, 15b can be fabricated in the form of an edge contact, as discussed with respect to Figure 1 b2,Figure 1 c2 and Figure 1 As explained by d2. Figure 4 The difference in the example is that the second stack 14 is also arranged on top of the first side 11a of the graphene layer 11, covering the first side 11a. The edge contact structures or electrodes 15a, 15b are in physical and electrical contact with the two lateral sides 11c, 11d (i.e., the edge portions) of the graphene layer 11.

[0063] In the example Figure 4 In some exemplary embodiments shown in b, one or more openings 14b, 14c may be formed in the insulating dielectric layer 14, thereby exposing the edges of the graphene film. More specifically, portions of the dielectric layer and / or graphene layer corresponding to one or more openings 14b, 14c are removed, exposing the edge portions 11c, 11d of the graphene film. Note that Figure 4 The openings 14b and 14c shown in Figure b are only for the purpose of conveying the purpose of edge contact deposition in the spaces formed due to material removal, without depicting any precise dimensions of the formed spaces or a specific sequence of the removal / deposition steps. It will be clear to those skilled in the art that the edge contacts are deposited after the openings are prepared. Furthermore, by depositing metal through the openings 14b and 14c in the insulating dielectric layer 14, electrical edge contacts 15a and 15b that are electrically and physically connected to the exposed edge portions 11c and 11d of the graphene film can be formed. Component 1 can be formed by adhesively bonding a cover or support layer 13 to the dielectric layer 14 on top of the graphene film 11 and the conductive first patterned structures 15a and 15b, as previously described and Figure 4 As shown in c. The substrate 200 (e.g., metal foil 200) is removed (i.e., detached) from the component 1, thereby exposing the graphene film 11 on the second side 11b at the bottom of the component 1, as shown. Figure 4 As shown in d.

[0064] In some exemplary embodiments, the graphene structure 1 or component 1 can be fabricated by forming a graphene film 11 on a substrate 200. Furthermore, a dielectric insulating layer 14 can be deposited on top of the graphene film 11 formed on the metal foil 200. A conductive gate structure (i.e., a first patterned structure 12 serving as a gate electrode 12) can be formed on top of the dielectric insulating layer 14. The dielectric insulating layer 14 can be referred to as the gate dielectric layer 14. Component 1 can be formed by adhesively attaching a supporting substrate 13 to the dielectric layer 14 and the gate electrode 12 on top of the graphene film 11. The substrate 200, including the metal foil, can be removed (detached) from component 1, thereby creating a barrier at the bottom of component 1 (i.e., as shown in the image). Figure 2 a to Figure 2The graphene film 11 is revealed (i.e. the exposed side of the graphene layer 11b shown in the example of d). Furthermore, in one or more post-processing steps, edge electrical contacts 15a, 15b can be formed in electrical and physical connection with the revealed side (i.e. edge portions 11c or 11d) of the graphene film 11. The cover layer 13 is depicted as serving as a support layer 13 on which the entire device 110 will rest.

[0065] Thus, in Figure 2 A graphene field effect transistor device 110 formed from and including the stacked graphene structure 1 is shown in e. The GFET 110 can be referred to herein as a back-gated GFET. The GFET 110 includes a graphene layer 11 having a first side 11a and a second side 11b opposite the first side. Furthermore, the GFET device 110 includes a gate dielectric layer stack 14 arranged at the first side 11a of the graphene layer. A first patterned gate electrode 12 can be arranged at a first side 14a of the gate dielectric layer stack 14. A support layer 13 is attached (e.g. by lamination or gluing) on the first patterned gate electrode 12 and the first side of the gate dielectric layer stack 14a. The attached cover layer 13 can be configured to enclose the first patterned gate electrode 12 and further support the first patterned gate electrode, the gate dielectric layer stack and the graphene layer. A second patterned electrode structure 15a, 15b including a first source electrode portion (e.g. electrode 15a) and a second drain electrode portion (e.g. electrode 15b) can be arranged at opposite ends (e.g. edge portions 11c, 11d) of the graphene layer 11 exposed at the second side 11b. It will be clear to the skilled person that devices 1, 110, 120, 130 according to several embodiments herein can be manufactured with top or edge contacts depending on the required design constraints and / or applications. The back-gated GFET device 110 can further include a cover dielectric layer 16 arranged at the second side 11b of the graphene layer and configured to cover the exposed second side 11b of the graphene layer 11, e.g. as shown in Figure 3 The device 120 in f and Figure 3The device 130 shown in g. In some example embodiments, the dielectric material 16 can be a Parylene N dielectric layer 16. With the methods presented herein, a scalable, sustainable and simpler fabrication of high quality graphene devices can be achieved. The patterning of the gate electrode on top of graphene on a copper substrate enables the fabrication of back-gated GFETs, which is traditionally done on Si / SiO2 substrates using conventional transfer methods. The most traditional method involves first transferring graphene using a wet transfer method (from copper) and then patterning the device. The microfabrication techniques used in the embodiments herein are significantly simpler, sustainable and economical compared to the traditional process flow used by the academic and industrial community. All the steps are highly scalable and suitable for mass production. The presented methods can also be used to stack multiple layers of graphene for various practical applications.

[0066] As previously mentioned, the graphene structure 1 can be detachably arranged on the substrate 200. Thus, in several aspects and embodiments herein, the stacked graphene structure 1 can be separated from the substrate 200 by detaching the stacked graphene structure 1 such that a second side 1 lb of the graphene layer 11 opposite the first side 11a of the graphene layer is exposed to an external environment, e.g. air. In several embodiments, the stacked graphene structure can be detached from the substrate 200 by means of electrochemical exfoliation. Additionally or alternatively, the stacked graphene structure 1 can be detached from the substrate 200 by mechanical exfoliation or an etching process, e.g. a wet chemical etching process by e.g. dilute nitric acid (HNO3), iron trichloride (FeCl3) or ammonium persulfate ((NH4)2S2O8).

[0067] The inventors have realized that the graphene layer 11, being a single layer of carbon atoms with a thickness of about 0.34 nm, is able to withstand several fabrication steps, resulting in a fabrication stack of several hundred nanometers on top of the graphene layer 11, which can comprise the first patterned structure 12, the second layer stack 14 (e.g. a dielectric layer), etc.

[0068] Very interestingly, according to the embodiments herein, the graphene retains its electrical and physical properties when the graphene layer and the patterned structure are released from the substrate 200 under the support of the capping layer 13.

[0069] Attachment of the capping layer over the graphene layer and the entire patterned structure still arranged on the substrate 200 is also a unique feature of the solution presented herein. Detachment (i.e. release) of the prepared graphene assembly 1 from the copper substrate 200 by electrochemical exfoliation or mechanical exfoliation provides an additional advantage of reusing the copper substrate 200, as the copper substrate 200 does not dissolve during the release process. This way, a more cost-effective and scalable manufacturing process can be achieved. Detachment of the prepared graphene assembly 1 from the copper substrate 200 by electrochemical exfoliation provides a further advantage of largely preserving the electronic properties of the graphene layer from being affected. Thus, the method, structure and device presented herein can achieve a significantly higher carrier mobility compared to the prior art, at least four times higher, or at least seven times higher, or at least eight times higher in some cases.

[0070] The released graphene structure 1 according to various exemplary embodiments herein is shown in Figure 1 dl、 Figure 1 d2、 Figure 2 d to Figure 2 e、 Figure 3 d to Figure 3 g and Figure 4 d. It should be noted that the inventors have realized that the capping layer 13 can be used as a base and support layer 13 over which the entire graphene structure 1 can rest in its released state.

[0071] According to several embodiments and aspects, one or more appropriate post-processing steps can also be performed on the released graphene structure 1 to complete the device comprising the graphene structure 1 for its intended application. For example, a second patterned structure 15 can be formed such that it can extend over the second side lib of the graphene layer 11 exposed after release. This is for example shown in structure 110 in Figure 2 e, where a pair of conductive edge contact electrodes 15a and 15b are formed in physical and electrical contact with both sides (i.e. edge portions lie, lid) of the graphene layer 11 when the second side of the graphene layer lib is exposed.

[0072] It should be noted that the first patterned structure 12 (e.g. top / edge contact electrodes 12) and / or the second layer stack 14, or the second patterned structure 15 (e.g. edge contact electrodes 15a, 15b shown in Figures 1 to 4 may have any suitable thickness, for example at least 10 nm, 20 nm, 50 nm, 100 nm, 200 nm or 300 nm, and / or at most 300 nm or 1000 nm, depending on the intended design and application.

[0073] In a similar example, as Figure 3 e、 Figure 3 f andFigure 3 g, the graphene structure 1 can undergo a post-processing step of arranging the third layer stack 16 by depositing the third layer stack 16 on top of the exposed second side lib of the graphene layer 11 separated from the substrate 200. This is shown in Figure 3 f to Figure 3 g for the structures 120 and 130. In this example, a pair of electrically conductive edge contacts 15a and 15b are formed in physical and electrical contact with both sides lie, lid of the graphene layer 11, while the second side lib of the graphene layer is covered by the third layer stack 16. In Figure 3 g, an additional second patterned structure 15c can be arranged on top of the first side 16a of the third layer stack 16 in the structure 130. In some example embodiments, the third layer stack 16 can be made of Parylene N dielectric material.

[0074] Thus, in some example embodiments, after the metal foil (e.g., copper foil) is removed from the assembly 1 and the second side lib of the graphene film is revealed at the bottom of the assembly, a packaging insulating layer 16 (e.g., a dielectric layer 16) can be arranged on the surface of the revealed graphene film. Furthermore, openings 16b, 16c can be formed in the packaging insulating layer 16, which reveal the edge portions lie, lid of the graphene film 11, as shown in Figure 3 f. The openings can be formed by any of the patterning methods as previously explained. Removing the portions of the graphene film corresponding to the openings through the openings in the packaging insulating dielectric layer 16 can form the side edges lie, lid of the graphene film. By depositing metal through the openings in the packaging insulating layer 16, edge electrical contacts 15a, 15b can be formed in electrical and physical connection with the revealed lateral edges lie, lid of the graphene film 11, as shown in Figure 3 f for the example graphene-based device 120.

[0075] In some example embodiments, an additional electrically conductive structure 15c can be deposited on the outer surface (i.e., side 16a) of the packaging insulating layer 16, as shown in Figure 3 g for the example graphene-based device 130. The additional electrically conductive structure 15c can be an electrically conductive gate structure 15c in the graphene-based transistor device 130.

[0076] As mentioned previously with respect to conventional fabrication techniques for graphene devices, after wet transfer of the graphene layer to the target substrate, electrodes are applied to the graphene layer by micro-nano fabrication processes such as photolithography, evaporation and lift-off. These metal electrodes are used to transmit electrical signals to and receive electrical signals from the graphene. In one method, contact electrodes are deposited on the wet transferred graphene on a Si / SiO2substrate. These contact electrodes are referred to as top contacts. In another method, referred to as bottom contacts, CVD graphene on a copper foil is transferred by a wet transfer method onto a target substrate (e.g. Si / SiO2substrate) with pre-deposited metal electrodes. The advantage of bottom contacts is to minimize additional processing to the already transferred graphene, thereby reducing surface contamination and improving electrical performance. However, conventional bottom contact devices still suffer from the above-mentioned disadvantages of wet transfer and contamination of the graphene onto the pre-deposited metal electrodes. Furthermore, in order to utilize graphene devices for chemical sensing in liquid media, the metal electrodes undergo an isolation process using an insulating material (e.g. metal oxide or polymer) to avoid parasitic currents. This involves an additional photolithographic patterning step to coat or grow the insulating material on the fabricated graphene device. Common isolation methods include spin-coating SU8 photoresist or deposition of metal oxide (e.g. AI2O3) using atomic layer deposition. However, these methods not only add additional steps to the fabrication of graphene devices, but also risk contaminating the graphene surface.

[0077] The present inventors have devised methods and techniques to overcome the above-mentioned disadvantages in depositing contact electrodes in conventional methods. According to the present application, as described herein Figure 1 a3 to Figure 1The embodiments and aspects shown in e3 provide a stacked graphene structure 1 detachably disposed and formed on a copper foil substrate 200. The stacked graphene structure includes a graphene layer 11 formed on the copper foil substrate 200. The stacked graphene structure 1 further includes a pre-patterned capping layer 131 permanently attached to the top of a first side 11a of the graphene layer 11. The pre-patterned capping layer 131 includes a first patterned structure 12 made of a conductive material and extending over the first side 13a of the capping layer 13 configured to support the first patterned structure 12. In other words, the pre-patterned capping layer 131 is formed by pre-patterning an electrode 12 deposited on the top of the first surface 13a of the capping layer 13. The conductive electrode 12 can be deposited on the first surface 13a of the capping layer 13 configured to support the patterned electrode 12 by means of metal evaporation, inkjet printing, screen printing, etc. The conductive material deposition layer 121 can be patterned using conventional photolithography or any other micro / nanofabrication method to form a patterned electrode 12 on the capping layer 13 and to form a pre-patterned capping layer 131. The pre-patterned capping layer 131 can then be attached to the top of the first side 11a of the graphene layer 11 formed on the substrate 200. In several embodiments, the first side 12a of the patterned electrode structure 12 and the first surface 13a of the capping layer 13 can be arranged to physically contact the first side 11a of the graphene layer formed on the substrate 200. Similar to... Figure 1 c1、 Figure 1 d1、 Figure 1 c2 and Figure 1The method shown in d2 eliminates the need for wet transfer of CVD graphene, thus advantageously preventing unnecessary contamination of the graphene layer 11. A pre-patterned capping layer 131 can be attached to the graphene layer 11 by adhesive bonding. Adhesive bonding of the pre-patterned capping layer 131 provides a permanent attachment between the capping layer 13 and the surface on which it is adhered. The first surface 13a of the permanently bonded pre-patterned capping layer 131 is arranged to be in physical contact with the surface on which it is adhered. The advantage of this arrangement is that the pre-patterned capping layer 131 serves as the final support substrate 13 (i.e., the base for forming the device), on which the entire device 1 will rest. More specifically, the top surface 13b of the pre-patterned capping layer 131 will serve as the bottom surface 13b of the final device 1. Similar to the capping layer 13, the pre-patterned capping layer 131 can be made of an insulating material, including any of plastics, thermoplastics, glass, sapphire, or other dielectric materials. In several embodiments, the pre-patterned cover layer 131 may comprise a plastic formed of a bilayer structure, the bilayer structure comprising a first sublayer made of ethylene-vinyl acetate (EVA) and a second sublayer made of polyethylene terephthalate (PET). In this example, the cover layer comprises a flexible cover layer 13, such as a bilayer PET / EVA combination having an integrated EVA adhesive layer 13-1 and a PET insulating layer 13-2, as... Figure 1 As shown in a3. When the pre-patterned overlay is brought into contact with the graphene layer ( Figure 1 c3), the adhesive layer 13-1 conforms to the morphology of the underlying graphene layer 11 and the patterned electrode 12, such as Figure 1 As shown in d3.

[0078] Similar to Figure 1 d1 and Figure 1 In implementation d2, the graphene structure 1, including the pre-patterned capping layer 131, can be separated from the copper substrate 200 by electrochemical exfoliation. Alternatively or additionally, the graphene structure 1 can be detached from the substrate 200 by mechanical exfoliation or an etching process (e.g., wet chemical etching). Figure 1 d3). The graphene layer 11 can then be patterned into the desired geometry using photolithography and oxygen plasma etching, such as... Figure 5 As shown in e3.

[0079] An additional advantage of the above method is the isolation between the metal electrode 12 and the graphene layer 11 itself, for use in electrochemical sensing in liquid media. The attached graphene layer, which is in physical contact with the pre-deposited metal electrode 12 of the capping layer 13, is arranged to act as an insulating layer. It should be noted that, in this document, isolation is not equivalent to electrical insulation.

[0080] This not only omits the additional step of the required isolation by an insulating material, but also avoids further contamination of the graphene layer 11 by additional processing steps.

[0081] In several embodiments, the stacked graphene structure 1 can be detached from the copper foil substrate 200 by several detachment processes, such as the electrochemical exfoliation method, the mechanical exfoliation method or the etching process as previously described. In several embodiments, the stacked graphene structure 1 can comprise a patterned graphene layer 111, wherein the patterned graphene layer 111 can be arranged to cover a first side 12a of the first patterned structure 12. Thus, a second side 11b of the patterned graphene layer 111 can be exposed.

[0082] Another advantage achieved by the method presented herein is the mitigation of the degradation of the electrical properties of graphene that is heavily affected by conventional wet transfer methods. For example, the measured charge carrier mobility of wet-transferred graphene on Si / Si02substrates is 1000 cm 2 / Vs, while using the above-described method, a charge carrier mobility of 10000 cm 2 / Vs is obtained in the graphene devices presented herein.

[0083] The presented method can be used to fabricate liquid-gated graphene field effect transistors with on-chip integrated metal electrodes. The integrated metal electrodes allow for the replacement of bulky external reference electrodes. The fabricated GFETs can be used to develop graphene-based infection diagnostic kits functionalized with receptors for captured infection biomarkers. The devices fabricated using the fabrication method disclosed herein are significantly superior to commercially available devices on Si / Si02using wet-transferred graphene in terms of electrical performance, flexibility and scalability of the fabrication process, and cost efficiency.

[0084] Figure 6 A flowchart of a method 500 according to several embodiments and aspects of the present disclosure is shown. The method 500 is presented for fabricating a stacked graphene structure 1. The method 500 comprises forming 501 a graphene layer 11 on a substrate 200. In several embodiments, the substrate can be a metal substrate, such as a metal foil. The metal foil can be a copper foil. The method further comprises forming 503 a first patterned structure extending over a first side of the graphene layer formed on the substrate. Further, the method comprises forming 505 a cover layer over the first patterned structure by attaching 505a the cover layer on the first patterned structure and the graphene layer formed on the substrate, wherein the stacked graphene structure comprises at least the graphene layer 11, the first patterned structure 12 and the attached cover layer 13.

[0085] In some embodiments, the method can further comprise forming the first patterned structure by depositing the first patterned structure on top of the first side of the graphene layer formed on the substrate.

[0086] In several embodiments, the method can further comprise attaching 505a the cover layer on top of the first side 12a of the first patterned structure 12 and the first side of the graphene layer formed on the substrate. More specifically, the method can comprise attaching 505a the cover layer 13 in physical contact with the first side 12a of the first patterned structure 12 by gluing the cover layer 13 on top of the first side 12a of the first patterned structure and the first side 11a of the graphene layer. The method can further comprise providing 506 permanent attachment of the cover layer 13 on top of the first side 12a of the first patterned structure and the first side of the graphene layer formed on the substrate.

[0087] In several embodiments, the method can further comprise forming 507 a second layer stack between the graphene layer 11 formed on the substrate and the first patterned structure 12 by depositing the second layer stack on top of the first side of the graphene layer formed on the substrate. The method can further comprise forming the first patterned structure on top of the first side 14a of the deposited second layer stack, wherein the stacked graphene structure can further comprise the second layer stack. In several embodiments, the second layer stack can be made of a dielectric material.

[0088] In several embodiments, the method can further comprise attaching 505a the cover layer on top of the first side of the first patterned structure and the deposited second layer stack. More specifically, the method 500 can comprise attaching 505a the cover layer 13 in physical contact with the first side 12a of the first patterned structure 12 and the first side 14a of the deposited second layer stack by gluing 505a the cover layer 13 on top of the first side 12a of the first patterned structure 12 and the first side 14a of the deposited second layer stack. Accordingly, the method can further comprise providing 506 permanent attachment of the cover layer 13 on top of the first side 12a of the first patterned structure 12 and the first side 14a of the deposited second layer stack.

[0089] In several exemplary embodiments, the first patterned structure can be made of a conductive material including a metal or a conductive ink, and the first patterned structure can be adapted to function as a conductive electrode.

[0090] In several embodiments, the cover layer can be made of an insulating material including any one of plastic, glass, or sapphire.

[0091] In several embodiments, the method can further comprise separating 509 the stacked graphene structure from the substrate by detaching 509 the stacked graphene structure. Such that a second side of the graphene layer opposite the first side of the graphene layer can be exposed. Exposing the second side of the graphene layer is to be understood as the second side being revealed and in direct communication with its surrounding environment, i.e. its immediate area.

[0092] In several embodiments, the method can further comprise detaching the stacked graphene structure from the substrate by any one of an electrochemical exfoliation method, a mechanical exfoliation method or an etching process.

[0093] In several embodiments, the method can further comprise forming 511 a third layer stack by depositing a third layer stack on top of the exposed second side of the graphene layer separated from the substrate. Additionally or alternatively, the method can further comprise forming 513 a second patterned structure extending above the second side of the graphene layer.

[0094] ​ A flowchart of a method 600 according to several embodiments and aspects of the present disclosure is shown. The method 600 is proposed for manufacturing a stacked graphene structure 1. The method 600 comprises forming 601 a first patterned structure 12 extending above a first side 13a of a cover layer 13 configured to support the first patterned structure 12. Thereby a pre-patterned cover layer 131 is formed 603 accordingly. The first patterned structure 12 can be made of a conductive material or a conductive ink comprising a metal. The first patterned structure can be adapted to function as a conductive electrode 12. The first patterned electrode structure 12 can be achieved by depositing a layer of conductive material on top of the first side 13a of the cover layer 13 and patterning the deposited layer by a photolithography method as previously described. The method 600 further comprises attaching 605 the pre-patterned cover layer 131 on the graphene layer 11 formed on a copper foil substrate 200, wherein the stacked graphene structure 1 comprises at least the graphene layer 11 and the attached pre-patterned cover layer 131.

[0095] In several embodiments, the method 600 can further comprise attaching 605a the pre-patterned cover layer 131 by gluing 605a the pre-patterned cover layer 131 on top of the first side 11a of the graphene layer. In this way, the first side 12a of the patterned electrode structure 12 and the first surface 13a of the cover layer 13 are arranged in physical contact with the first side 11a of the graphene layer 11. Thereby, the method can further comprise providing 606 a permanent attachment of the pre-patterned cover layer 131 on top of the first side 11a of the graphene layer 11.

[0096] In several embodiments, the method 600 can further comprise separating 607 the stacked graphene structure 1 from the copper foil substrate 200 by detaching 607 the stacked graphene structure. Such that a second side 1 lb of the graphene layers 11 opposite the first side 1 lb of the graphene layers 11 can be exposed. Exposing the second side of the graphene layers is understood to mean that the second side is revealed and in direct communication with its surrounding environment (i.e. its immediate area). In several embodiments, the method 600 can further comprise detaching the stacked graphene structure from the substrate by any one of an electrochemical exfoliation method, a mechanical exfoliation method, or an etching process.

[0097] In some embodiments, the method 600 can comprise patterning 609 the graphene layers 11 in the detached stacked graphene structure 1 to form patterned graphene layers 111. The patterned graphene layers 111 can be arranged to cover the first side 12a of the first patterned structure 12, and wherein a second side 1 lb of the patterned graphene layers (111) can be exposed.

[0098] In several embodiments, the above-mentioned surrounding environment can be a liquid medium. Thus, the graphene devices presented herein can be used for chemical sensing in liquid media. The exposed portions 1 lb of the graphene layers and the electrodes 12 can interface with a biological environment (e.g. a tissue portion). Thus, the devices can be used to read electrical or electrochemical signals from the tissue and its surrounding environment, operate as a biosensor, and transmit a stimulating electrical signal to the tissue.

[0099] In several embodiments, the patterned graphene layers 111 can have portions (not specifically shown) that are not arranged on the patterned electrodes 12 but on other portions of the bottom side 13a of the cover layer 13. In various embodiments, the graphene layers can be used as isolation layers for the electrodes 12.

[0100] It is to be understood that the above description is only a detailed example and is not intended to limit the present disclosure, its application, or uses. While specific examples have been described in the specification and exemplified in the accompanying drawings, it is to be understood that the same are presented by way of example only and not limitation, and various changes can be made without departing from the scope of the disclosure as defined in the claims. Where methods are described in the specification and examples, it is to be understood that the order of steps can be modified without departing from the scope of the disclosure. Accordingly, where a particular step is recited, it should be appreciated that the step can be performed prior to, after, or during another step. Moreover, it should be appreciated that the various steps could be performed by different entities, and that the steps could be performed in any suitable order. In addition, modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from its scope. The various graphene structures and devices presented herein can be advantageously manufactured using any of the embodiments of the presented manufacturing methods 500 or 600.

[0101] Accordingly, the disclosure is intended to be illustrative, but not limiting, of the scope of the application, which is set forth with particularity in the following claims. Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearance of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

Claims

1. A method (500) of manufacturing a stacked graphene structure (1), the method comprising: forming a graphene layer (11) on a copper foil substrate (200); forming a first patterned structure (12) extending over a first side (11a) of the graphene layer formed on the copper foil substrate; forming a cover layer (13) over the first patterned structure by attaching the cover layer on the first patterned structure and the graphene layer; wherein the stacked graphene structure comprises at least the graphene layer, the first patterned structure and the attached cover layer.

2. The method (500) of claim 1, wherein the method further comprising: forming the first patterned structure (12) by depositing the first patterned structure on top of the first side (11a) of the graphene layer.

3. The method (500) of any one of claims 1 or 2, wherein, the method further comprising: attaching the cover layer (13) in physical contact with the first side (12a) of the first patterned structure (12) and the first side (11a) of the graphene layer by gluing the cover layer (13) on top of the first side (12a) of the first patterned structure and the first side (11a) of the graphene layer; and thereby providing permanent attachment of the cover layer (13) on top of the first side (12a) of the first patterned structure and the first side of the graphene layer.

4. The method (500) of claim 1, wherein the method further comprising: forming a second layer stack (14) made of Parylene N dielectric material between the graphene layer formed on the substrate and the first patterned structure by depositing the second layer stack on top of the first side (11a) of the graphene layer formed on the copper foil substrate; and forming the first patterned structure on top of a first side (14a) of the deposited second layer stack; wherein the stacked graphene structure further comprises the second layer stack.

5. The method (500) of claim 4, wherein, the method further comprising: attaching the cover layer in physical contact with the first side (12a) of the first patterned structure (12) and the first side (14a) of the deposited second layer stack (14) by gluing the cover layer on top of the first side (12a) of the first patterned structure (12) and the first side (14a) of the deposited second layer stack (14); and thereby providing permanent attachment of the cover layer (13) on top of the first side (12a) of the first patterned structure (12) and the first side (14a) of the deposited second layer stack.

6. The method (500) of any one of claims 1 to 5, wherein, the first patterned structure (12) comprises a conductive material or a conductive ink, the conductive material comprising a metal, and the first patterned structure is adapted to function as a conductive electrode.

7. The method (500) according to any of the preceding claims, wherein the cover layer (13) comprises an insulating material, the insulating material comprising any one of a plastic, a thermoplastic, a glass or a sapphire, and wherein the cover layer is arranged to form a base on which the stacked graphene structure (1) is to rest.

8. The method (500) of claim 7, wherein, The cover layer (13) comprises plastic formed by a double layer structure comprising a first sub-layer (13-1) made of ethylene-vinyl acetate EVA and a second sub-layer (13-2) made of polyethylene terephthalate PET.

9. The method (500) according to any of the preceding claims, wherein The method further comprises: separating the stacked graphene structure (1) from the copper foil substrate (200) by detaching the stacked graphene structure (1) such that a second side (lib) of the graphene layer opposite the first side (11a) of the graphene layer is exposed.

10. The method (500) of claim 9, wherein, The method further comprises: detaching the stacked graphene structure from the copper foil substrate by any one of: an electrochemical exfoliation method, a mechanical exfoliation method, or an etching process.

11. The method (500) of any one of claims 9 or 10, wherein, The method further comprises: forming the third layer stack by depositing a third layer stack (16) on top of the exposed second side (lib) of the graphene layer separated from the copper foil substrate; and / or forming a second patterned structure (15) extending over the second side of the graphene layer.

12. A stack of graphene structures (1) which are detachably arranged and formed on a copper foil substrate (200), wherein, The graphene structure comprises: a graphene layer (11) formed on the substrate; a first patterned structure (12) extending over a first side (11a) of the graphene layer formed on the substrate; and a cover layer (13) attached on the first patterned structure and the graphene layer.

13. The stacked graphene structure of claim 12, wherein, The graphene structure further comprises: a second layer stack (14) made of Parylene N dielectric material arranged between the graphene layer and the first patterned structure, the second layer stack deposited on top of the first side of the graphene layer; wherein the first patterned structure is arranged on top of a first side (14a) of the deposited second layer stack.

14. A graphene-based sensor device (110) or a graphene field effect transistor device (110, 120, 130) comprising a stacked graphene structure manufactured by the method according to any one of claims 1 to 11.

15. A graphene field effect transistor device (110, 120, 130) formed by the method according to any one of claims 1 to 13 and comprising a stacked graphene-based structure (1) according to any one of claims 1 to 13, the transistor device comprising: a graphene layer (11) having a first side (11a) and a second side (lib) opposite the first side; a gate dielectric layer stack (14) made of Parylene N arranged on the first side (11a) of the graphene layer; a first patterned gate electrode (12) arranged on a first side (14a) of the gate dielectric layer stack (14); a cover layer (13) attached on the first patterned gate electrode and the first side of the gate dielectric layer stack, the attached cover layer configured to enclose the first patterned gate electrode and further support the first patterned gate electrode, the gate dielectric layer stack, and the graphene layer; a second patterned electrode structure (15) comprising a first source electrode portion (15a) and a second drain electrode portion (15b) arranged at opposite ends (11c, 11d) of the graphene layer; wherein the second side (lib) of the graphene layer is exposed.

16. The graphene field effect transistor device according to claim 15, wherein the transistor device further comprises: a cover dielectric layer (16) arranged at the second side (lib) of the graphene layer and configured to cover the exposed second side of the graphene layer.

17. A method (600) of manufacturing a stacked graphene structure (1), the method comprising: forming a first patterned structure (12) extending over a first side (13a) of a cover layer (13) configured to support the first patterned structure (12), thereby forming a pre-patterned cover layer (131); wherein the first patterned structure (12) is made of an electrically conductive material; attaching the pre-patterned cover layer (131) on a graphene layer (11) formed on a copper foil substrate (200), wherein the stacked graphene structure (1) comprises at least the graphene layer (11) and the attached pre-patterned cover layer (131).

18. The method (600) of claim 17, wherein the method further comprising: attaching the pre-patterned cover layer (131) by gluing the pre-patterned cover layer (131) on top of the first side (11a) of the graphene layer; such that the first side (12a) of the patterned electrode structure (12) and the first surface (13a) of the cover layer (13) are arranged in physical contact with the first side (11a) of the graphene layer; thereby providing a permanent attachment of the pre-patterned cover layer (131) on top of the first side (11a) of the graphene layer (11).

19. The method (600) of any one of claims 17 or 18, wherein, the method further comprising: separating the stacked graphene structure from the copper foil substrate (200) by detaching the stacked graphene structure (1), such that a second side (lib) of the graphene layer (11) opposite the first side (lib) of the graphene layer (11) is exposed.

20. The method (600) of claim 19, wherein the method further comprising: patterning the graphene layer (11) in the detached stacked graphene structure (1) to form a patterned graphene layer (111), wherein the patterned graphene layer (111) is arranged to cover the first side (12a) of the first patterned structure (12), and wherein the second side (lib) of the patterned graphene layer (111) is exposed.

21. The method (600) of any of claims 17 to 20, wherein the pre-patterned cover layer (131) comprises an insulating material comprising any one of plastic, thermoplastic, glass or sapphire, and wherein the pre-patterned cover layer (131) is arranged to form a base on which the stacked graphene structure (1) is to rest.

22. The method (600) of claim 21, wherein The pre-patterned cover layer (131) comprises plastic formed by a double layer structure comprising a first sub-layer (13-1) made of ethylene-vinyl acetate EVA and a second sub-layer (13-2) made of polyethylene terephthalate PET.

23. A stack of graphene structures (1) which are detachably arranged and formed on a copper foil substrate (200), wherein, The graphene structure comprises: a graphene layer (11) formed on the copper foil substrate (200); a pre-patterned cover layer (131) permanently attached on top of a first side (11a) of the graphene layer (11), wherein the pre-patterned cover layer comprises a first patterned structure (12) made of electrically conductive material and extending over a first side (13a) of the pre-patterned cover layer (131) configured to support the first patterned structure (12).

24. The stacked graphene structure (1) according to claim 21, wherein, When the stacked graphene structure (1) is separated from the copper foil substrate (200), the stacked graphene structure (1) comprises: a patterned graphene layer (111), wherein the patterned graphene layer (111) is arranged to cover a first side (12a) of the first patterned structure (12), and wherein a second side (11b) of the patterned graphene layer (111) is exposed.

25. A graphene-based sensor device (1) comprising a stacked graphene structure (1) manufactured by the method according to any one of claims 17 to 22.

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