Patent Publication Number: US-11658232-B2

Title: Field effect transistor based on graphene nanoribbon and method for making the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to commonly-assigned application entitled, “GRAPHENE NANORIBBON COMPOSITE STRUCTURE AND METHOD FOR MAKING THE SAME”, concurrently filed; “FIELD EFFECT TRANSISTOR AND METHOD FOR MAKING THE SAME”, concurrently filed. The entire contents of which are incorporated herein by reference. 
     FIELD 
     The present application relates to a field effect transistor and a method for making the field effect transistor. 
     BACKGROUND 
     The field effect transistor (abbreviated as FET) has two main types: junction FET-JFET and metal-oxide semiconductor FET (abbreviated as MOS-FET). The field effect transistor is a voltage-controlled semiconductor device. The field effect transistor has the advantages of high input resistance, low noise, and low power, and has become a strong competitor of bipolar transistors and power transistors. 
     The material for forming the semiconductor layer of the field effect transistor is amorphous silicon or polysilicon. The preparation technology of amorphous silicon field effect transistor using amorphous silicon as the semiconductor layer is relatively mature. However, in the amorphous silicon field effect transistor, the semiconductor layer usually contains a large number of dangling bonds, resulting in low carrier mobility and a slower response speed of the field effect transistor. The field effect transistor using polysilicon as the semiconductor layer has a higher carrier mobility than the field effect transistor using amorphous silicon as the semiconductor layer, so the response speed is also faster. However, the low-temperature production cost of the polysilicon field effect transistor is relatively high, the method for making the polysilicon field effect transistor is more complicated, and large-area production of the polysilicon field effect transistor is difficult. 
     Therefore, there is room for improvement in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of embodiments, with reference to the attached figures, wherein: 
         FIG.  1    shows a schematic process flow of a method for making a graphene nanoribbon composite structure in a first embodiment. 
         FIG.  2    shows an atomic force microscope (AFM) image of a second composite structure in the first embodiment. 
         FIG.  3    shows a scanning electron microscope (SEM) image of the graphene nanoribbon composite structure of  FIG.  1   . 
         FIG.  4    shows an AFM image of the graphene nanoribbon composite structure of  FIG.  1   . 
         FIG.  5    shows a schematic top view of the graphene nanoribbon composite structure of  FIG.  1   . 
         FIG.  6    shows a schematic process flow of a method for making a graphene nanoribbon composite structure in a second embodiment. 
         FIG.  7    shows a schematic process flow of a method for making a graphene nanoribbon composite structure in a third embodiment. 
         FIG.  8    shows a schematic process flow of a method for making a graphene nanoribbon composite structure in a fourth embodiment. 
         FIG.  9    shows a schematic process flow of a method for making a field effect transistor in a fifth embodiment. 
         FIG.  10    shows a schematic view of the graphene nanoribbons electrically connected with the source electrodes and the drain electrodes in the fifth embodiment. 
         FIG.  11    shows a schematic view of the field effect transistor in the fifth embodiment. 
         FIG.  12    shows a schematic process flow of a method for making a field effect transistor in a sixth embodiment. 
         FIG.  13    shows a schematic view of the field effect transistor in the sixth embodiment. 
         FIG.  14    shows a schematic process flow of a method for making a field effect transistor in a seventh embodiment. 
         FIG.  15    shows a schematic view of an interdigital electrode in the seventh embodiment. 
         FIG.  16    shows a schematic top view of the field effect transistor in the seventh embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale, and the proportions of certain parts may be exaggerated to illustrate details and features better. The description is not to be considered as limiting the scope of the embodiments described herein. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
     An infrared absorber of a first embodiment is a carbon nanotube structure formed by stacking a plurality of drawn carbon nanotube films. 
     Referring to  FIG.  1   ,  FIG.  2   , and  FIG.  5   , a method for making a graphene nanoribbon composite structure  20  of a first embodiment, includes one or more of the following steps: 
     S 11 , locating a mask layer  12  on a base  10 , wherein the mask layer  12  has a first surface  122  and a second surface  124  opposite to the first surface  122 , the first surface  122  is in direct contact with the base  10 , the mask layer  12  defines a plurality of through holes  126  spaced apart from each other, the through holes  126  extend from the first surface  122  to the second surface  124 , an X direction and a Y direction are defined on the surface of the base  10 , and the X direction and the Y direction are perpendicular to each other; 
     S 12 , locating a metal layer  14  on the second surface  124 , wherein the through holes  126  are filled with the metal layer  14 ; 
     S 13 , peeling off the mask layer  12 , wherein the metal layer  14  on the second surface  124  is also removed while peeling off the mask layer  12 , and the metal layers  14  in the through holes  126  remain on the base  10 ; 
     S 14 , using the metal layer  14  remaining on the base  10  as a mask, and etching the base  10 ; 
     S 15 , removing the metal layer  14  remaining on the base  10  to obtain a structure  16 , wherein the structure  16  comprises a substrate body  162  and a plurality of protrusions  164  spaced apart from each other, the protrusions  164  are located on the surface of the substrate body  162 ; 
     S 16 , growing a graphene film  13  on a growth substrate  11 ; 
     S 17 , locating an adhesive layer  15  on the surface of the graphene film  13  away from the growth substrate  11 , removing the growth substrate  11 , and washing with water or organic solvent; 
     S 18 , taking the graphene film  13  and the adhesive layer  15  out of the water or the organic solution by using the substrate  16 , and drying, to obtain a first composite structure  17 , wherein the first composite structure  17  includes the substrate  16 , the graphene film  13 , and the adhesive layer  15 ; the graphene film  13  is located between the adhesive layer  15  and the substrate  16 , and the graphene film  13  is in direct contact with the protrusions  164 ; 
     S 19 , removing the adhesive layer  15  to obtain a second composite structure  19 , wherein the second composite structure  19  includes the substrate  16  and the graphene film  13 , the graphene film  13  is located on the surfaces of the protrusions  164  and the surface of the substrate body  162  between two adjacent protrusions  164 ; and the graphene film  13  forms a plurality of wrinkles  18  near the protrusions  164 , the wrinkles  18  are located on the surface of the substrate body  162  between the adjacent protrusions  164 , the wrinkles  18  extend substantially along the Y direction, and the thickness of the graphene film  13  at the wrinkle  18  is greater than the thickness of the graphene film  13  on the surface of the substrate body  162  between adjacent protrusions  164 ; and 
     S 20 , etching from the surface of the graphene film  13  away from the substrate  16 , to remove the graphene films  13  on the protrusions  164  and the graphene film  13  on the surface of the substrate body  162  between the adjacent protrusions  164  except for the wrinkles  18 , thereby obtaining the graphene nanoribbon composite structure  20 , wherein the graphene nanoribbon composite structure  20  includes the substrate body  162 , the plurality of protrusions  164 , and a plurality of graphene nanoribbons  22  parallel to each other; and the plurality of graphene nanoribbons  22  are spaced apart from each other and located on the substrate body  162 . 
     During step S 11 , the material of the base  10  can be conductive material, semiconducting material or insulating material. The material of the base  10  can be gallium nitride, gallium arsenide, sapphire, aluminum oxide, magnesium oxide, silicon, silicon dioxide, silicon nitride, quartz, glass, or the like. The material of the base  10  can also be flexible material, such as polyethylene terephthalate (PET) or polyimide (PI). Further, the material of the base  10  can also be a doped semiconductor material, such as P-type gallium nitride, N-type gallium nitride, and the like. The size, thickness and shape of the base  10  are not limited and can be selected according to actual needs. In one embodiment, the material of the base  10  is silicon oxide. In another embodiment, the base  10  is a silicon wafer with silicon oxide, the silicon oxide is located on the surface of the silicon wafer, and a thickness of the silicon oxide is about 300 nm. 
     The material of the mask layer  12  is not limited, and can be ZEP520A, HSQ (hydrogen silsesquioxane), PMMA (Polymethylmethacrylate), PS (Polystyrene), SOG (Silicon on glass), MMA (Methyl methacrylate) or other silicone oligomer materials. The mask layer  12  can be formed by depositing on the surface of the base  10  and then drying, or can be formed by a screen printing method. In one embodiment, the material of the mask layer  12  is PMMA. 
     The method for defining the plurality of through holes  126  on the mask layer  12  is not limited. In one embodiment, the electron beam exposure is used to form a through hole array. In one embodiment, a diameter of each through hole  126  is about 40 nm, a distance between two adjacent through holes  126  in each column is less than 500 nm, and a distance between two adjacent columns is greater than 500 nm. In the X direction, the distance between two adjacent through holes  126  is greater than 500 nm; in the Y direction, the distance between two adjacent through holes  126  is less than 500 nm. The shape of the through hole  126  is not limited, and can be a circle, a square, a triangle, or the like. 
     During step S 12 , the metal layer  14  can be deposited on the second surface  124  of the mask layer  12  by many methods, such as electron beam evaporation, ion beam sputtering, or the like. The metal layer  14  is also located in the through holes  126 . The material of the metal layer  14  is a metal that can be removed by an etching solution, and the material of the metal layer  14  can be iron, gold, chromium, copper, or aluminum. The thickness of the metal layer  14  is not limited. In one embodiment, the metal layer  14  is a copper layer with a thickness of about 15 nm. 
     During step S 13 , the method for peeling off the mask layer  12  is not limited, such as using tweezers and other tools to peel off the mask layer  12 . The mask layer  12  can be removed by dissolving the mask layer  12  in the organic solvent. 
     During step S 14 , the metal layer  14  that remains on the base  10  in the step S 13  is used as a mask, and the base  10  is dry-etched by reactive ion etching (RIE), so that the plurality of protrusions  164  are formed on the base  10 . The metal layer  14  that remains on the base  10  covers the plurality of protrusions  164 . In one embodiment, the etching depth is about 15 nm, and the height of the protrusion  164  is about 15 nm. 
     During step S 15 , the metal layer  14  that remains on the substrate  10  is removed with the etching solution. The metal layer  14  that remains on the substrate  10  is removed by a wet etching method. The type of the etching solution can be selected according to different materials of the metal layer  14 . In one embodiment, the metal layer  14  is a copper layer; the etching solution is sulfuric acid, nitric acid, hydrochloric acid, or a mixture; and the mixture is formed by hydrogen peroxide, hydrochloric acid, and deionized water (the volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is 1:1:50). In one embodiment, the plurality of protrusions  164  are arranged in order, the direction of each row is defined as the X direction, and the direction of each column is defined as the Y direction. The protrusions  164  in each row extend along the X direction, and the protrusions  164  in each column extend along the Y direction. The shape of the protrusion  164  is not limited, and can be a circle, a square, a triangle, or the like. In one embodiment, the protrusion  164  is a cylinder with a diameter of about 40 nm and a height of about 15 nm. 
     During step S 16 , the method of growing the graphene film  13  on the growth substrate  11  is not limited. The material of the growth substrate  11  can be copper, and the size of the growth substrate  11  is not limited and can be selected according to actual conditions. In one embodiment, the growth substrate  11  is a copper sheet. In one embodiment, the method of growing the graphene film  13  on the growth substrate  11  includes the following steps: 
     S 161 , depositing a catalyst layer on the growth substrate  11 ; and 
     S 162 , placing the growth substrate  11  with the catalyst layer in a chamber, supplying the carbon source gas into the chamber, and heating the growth substrate  11 , thereby forming the graphene film  13  on the growth substrate  11 . 
     During step S 161 , a metal or metal compound material is deposited on the surface of the growth substrate  11  to form the catalyst layer. The metal can be one of gold, silver, copper, iron, cobalt and nickel, or any combination thereof. The metal compound may be one of zinc sulfide, zinc oxide, iron nitrate, iron chloride, copper chloride, or any combination thereof. A method for depositing the catalyst layer on the growth substrate  11  is not limited, such as chemical vapor deposition, physical vapor deposition, vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition, or printing. 
     During step S 162 , the chamber can provide a reaction space for growing the graphene film  13 . The chamber can have a sealed cavity. The chamber includes a gas inlet and a gas outlet. The gas inlet is used to input a reaction gas or other resource gas. The gas outlet is connected with an evacuating device. The evacuating device can be used to adjust the pressure in the chamber. Furthermore, the chamber can include a water cooling device to adjust the temperature in the chamber. The chamber can be a quartz tube furnace. 
     The chamber is evacuated before heating the growth substrate  11 . In one embodiment, hydrogen gas can be introduced in the chamber through the gas inlet before heating the growth substrate  11 . The hydrogen gas can prevent the growth substrate  11  from oxidizing. The carbon source gas can be at least one of methane, ethane, ethylene, or acetylene. A flow rate of the carbon source gas can be in a range from about 20 standard cubic centimeters per minute (sccm) to about 90 sccm. The chamber is heated to a heating temperature that can be in a range from about 800 degrees Celsius to about 1000 degrees Celsius. The chamber is held at the heating temperature for a constant temperature period for about 10 minutes to about 60 minutes. A ratio between the flow rate of the carbon source gas and the hydrogen gas is in a range from about 45:2 to about 15:2. A pressure in the chamber can be in a range from about 10 −1  Pa to about 10 2  Pa. In one embodiment, the pressure of the chamber is about 500 mTorr, the temperature of the chamber is about 1000 degrees Celsius, the flow rate of the carbon source gas is about 25 sccm, the carbon gas is methane, and the constant temperature period is about 30 minutes. 
     During step S 17 , the material of the adhesive layer  15  is not limited. In one embodiment, the material of the adhesive layer  15  is PMMA (methyl methacrylate). The method for removing the growth substrate  11  is not limited, for example, the growth substrate  11  is removed by chemical etching. The material of the growth substrate  11  is copper, and the etching solution used to remove the growth substrate  11  is sulfuric acid, nitric acid, hydrochloric acid, or a mixture. The mixture is formed by hydrogen peroxide, hydrochloric acid and deionized water (the volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is 1:1:50). In one embodiment, the material of the growth substrate  11  is copper, and the etching solution used to remove the growth substrate  11  is a mixed solution composed of hydrogen peroxide, hydrochloric acid and deionized water (the volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is 1:1:50). After the growth substrate  11  is removed, the water or the organic solvent can be used to remove residual impurities. The water is preferably deionized water. The type of the organic solvent is not limited, such as isopropanol. 
     During step S 18 , in the process of taking the graphene film  13  and the adhesive layer  15  out of the water or the organic solution by using the substrate  16 , the substrate  16  is in direct contact with the graphene film  13 , and the adhesive layer  15  is located on the surface of the graphene film  13  away from the substrate  16 . Before drying, the water or organic solvent separates the graphene film  13  from the substrate  16 , and the water or the organic solvent is between the graphene film  13  and the substrate  16 . As the moisture (water) or the organic solvent evaporates, a vacuum state is gradually formed between the graphene film  13  and the substrate  16 , and the graphene film  13  is thus closely attached to the substrate  16 . The plurality of protrusions  164  are on the substrate body  162 , thus the graphene film  13  cannot be smoothly attached to the substrate body  162 , therefore wrinkles  18  are formed near the protrusions  164 . After combining the graphene film  13 , the adhesive layer  15 , and the substrate  16 , and before drying, the vacuum state between the grapheme film  13  and the substrate  16  is formed when water or organic solvent between the graphene film  13  and the substrate  16  evaporates; and the plurality of winkles  18  are formed on the grapheme film  13  by the plurality of protrusions  164  protruding from the substrate body  162 . 
     The wrinkles  18  are located on the surface of the substrate body  162  between adjacent protrusions  164  and extend along the Y direction, and the thickness of the graphene film  13  at the wrinkles  18  is greater than the thickness of the graphene film  13  on the surface of the substrate body  162  between adjacent protrusions  164 . In one embodiment, there are two layers of graphene film  13  at each wrinkle  18 , and one layer of graphene film  13  is formed on the surface of the substrate body  162  between adjacent protrusions  164 . In one embodiment, after taking the graphene film  13  and the adhesive layer  15  out of water or organic solution by using the substrate  16 , the graphene film  13  and the adhesive layer  15  are naturally dried for 3 hours to 6 hours, and then baked at a temperature of 150 degrees Celsius for 2 minutes. 
     The distance between two adjacent protrusions  164  in the Y direction is smaller than the distance between two adjacent protrusions  164  in the X direction, so that the plurality of wrinkles  18  are formed in the Y direction and the wrinkles  18  extend along the Y direction. The distance between two adjacent protrusions  164  in the X direction is in a range from about 200 nanometers to about 1 micron, and the distance between two adjacent protrusions  164  in the Y direction is in a range from about 100 nanometers to about 800 nanometers. In one embodiment, the distance between two adjacent protrusions  164  in the X direction is about 1 micron, and the distance between two adjacent protrusions  164  in the Y direction is about 500 nanometers. In one embodiment, the distance between two adjacent protrusions  164  in the X direction is 1 micron, and the distance between two adjacent protrusions  164  in the Y direction is 500 nanometers. 
     During step S 19 , the method for removing the adhesive layer  15  is not limited, for example, the adhesive layer  15  is dissolved using the organic solvent. The first composite structure  17  has one more adhesive layer  15  than the second composite structure  19 . In one embodiment, the material of the adhesive layer  15  is PMMA, and acetone is used to remove PMMA. In one embodiment, the organic solvent is used to remove the adhesive layer  15 , after taking the adhesive layer  15  out of the organic solution, the adhesive layer  15  is annealed. The effect of annealing is to remove residual adhesive layer  15  on the surface of the graphene film  13  during transferring the graphene film  13 . In one embodiment, the annealing conditions are as follows: hydrogen and argon are introduced under vacuum, the pressure is about 2 Pa, and annealing is performed at about 400 degrees Celsius for about 2 hours. In one embodiment, the annealing pressure is 2 Pa, and annealing is performed at 400 degrees Celsius for 2 hours. In one embodiment, the wrinkles  18  extend along the Y direction. 
     During step S 20 , etching is performed from the surface of the graphene film  13  away from the substrate  16 , so that the graphene film  13  located on the protrusions  164  and the graphene film  13  located on the surface of the substrate body  162  between two adjacent protrusions  164 , except for the wrinkles  18 , are removed. When the graphene film  13  on the surface of the substrate body  162  between the adjacent protrusions  164 , rather than the wrinkle  18 , is etched, the graphene film  13  at the wrinkle  18  is also etched at the same time. The thickness of the graphene film  13  at the wrinkle  18  is greater than the thickness of the graphene film  13  on the surface of the substrate body  162  between two adjacent protrusions  164 . Thus, when the graphene film  13  located on the protrusions  164  and the graphene film  13  located on the surface of the substrate body  162  between two adjacent protrusions  164 , except for the wrinkles  18 , are completely etched and removed, the graphene still exists at the wrinkles  18 , so that graphene nanoribbons  22  are formed at the wrinkles  18 . In one embodiment, RIE is used for etching in the step S 20 , and the etching conditions are: the volume flow of hydrogen is about 50 sccm, the pressure is about 5 Pa, the power is about 5 W (watts), and the etching time is about 50 s (seconds). In one embodiment, the etching conditions of RIE are: the volume flow of hydrogen is 50 sccm, the pressure is 5 Pa, the power is 5 W, and the etching time is 50 s. 
     Furthermore, the plurality of protrusions  164  may also be removed by etching. The preparation method of the graphene nanoribbon composite structure  20  further includes a step of removing the plurality of protrusions  164  by etching. 
     In one embodiment, a silicon wafer with 300 nm thick SiO 2  layer on the surface of the silicon wafer as the base  10 . PMMA electron beam glue is spin-coated on the surface of the SiO 2  layer away from the silicon wafer, and the SiO 2  layer is in direct contact with PMMA. The thickness of the PMMA is about 80 nm. The electron beam exposure and development are performed. The exposure pattern is an array having a plurality of through holes, and the array is made of the PMMA. The diameter of each through hole is about 40 nm, a distance between two adjacent through holes in each column of the through hole array is about 500 nm, and a distance between two adjacent columns is about 500 nm. Afterwards, electron beam evaporation is used to deposit copper with a thick of about 15 nm, and then PG solution is used to remove the PMMA glue and partial copper is also removed when removing the PMMA glue, to form a copper pillar array having a plurality of copper pillars. The diameter of each copper pillar is about 40 nm, a distance between two adjacent copper pillars in each column is about 500 nm, and a distance between two adjacent columns is about 500 nm. Then, the copper pillar array is used as a mask to etch the base  10 , and finally the copper pillars is removed to obtain the substrate  16  with an array structure. The protrusions  164  on the substrate  16  are cylindrical with a diameter of about 40 nm and a height of about 15 nm. 
     When transferring graphene, PMMA is first spin-coated on a copper foil grown with a single layer of graphene at a rotation speed of 3000 rpm, and then baked on a hot plate at 180 degrees Celsius for 2 minutes to volatilize the solvent. In the process of growing graphene, graphene will grow on two opposite surfaces of the copper foil, and the graphene structure on the back of the copper foil is incomplete and needs to be removed. Therefore, RIE is used to remove the graphene on the back of the copper foil. The etching conditions are: oxygen etching, pressure of about 2 Pa, flow rate of about 40 sccm, power of about 50 W, and etching time of about 30 seconds. Next, the copper foil is put in the etching solution. The etching solution is a mixture of hydrochloric acid, hydrogen peroxide and deionized water, and the volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is 1:1:50. After the copper foil is completely etched, the graphene and PMMA film are cleaned several times with deionized water. Then, the graphene and PMMA film are picked up using the substrate  16  and leave for 6 hours to evaporate the water. Then, the substrate  16  is baked for 2 minutes using the hot plate at 150 degrees Celsius, to obtain a sample. The sample is then put into an acetone solution and soaked for 10 minutes, and then taken out, the sample is cleaned with deionized water, and the water of the surface of the sample is blown off with nitrogen. Finally, the substrate  16  with graphene is put into an annealing furnace for annealing, and the annealing conditions are: the flow rate of H 2  is about 100 sccm, the flow rate of Ar is about 100 sccm, and annealing is performed at 400 degrees Celsius for 2 hours, so that the graphene nanoribbon composite structure  20  is formed. 
       FIG.  2    is an atomic force microscope (AFM) image of the second composite structure  19 . It can be seen from  FIG.  2    that one wrinkle  18  is formed near each protrusion  164 , the wrinkle  18  is located on the surface of the substrate body  162  between two adjacent protrusions  164 , the wrinkle  18  extends from one protrusion  164  to the adjacent protrusion  164 , and the extending directions of the plurality of wrinkles  18  are substantially parallel to each other. In one embodiment, the extending directions of the plurality of wrinkles  18  are parallel to each other. 
       FIG.  3    is a scanning electron microscope (SEM) image of the graphene nanoribbon composite structure  20  in the step S 20 .  FIG.  4    is an AFM image of the graphene nanoribbon composite structure  20  in the step S 20 . In  FIG.  4   , in the longitudinal direction, the ribbon-like structure between adjacent dots is the graphene nanoribbon  22 . The plurality of graphene nanoribbons  22  are arranged at intervals, extend in the same direction and are parallel to each other. 
     Referring to  FIG.  4    and  FIG.  5   , the graphene nanoribbon composite structure  20  includes the substrate  16  and the plurality of graphene nanoribbons  22  spaced apart from each other, and the plurality of graphene nanoribbons  22  are located on the substrate  16  and extend substantially along the same direction. The substrate  16  includes the substrate body  162  and the plurality of protrusions  164  spaced apart from each other, and the plurality of protrusions  164  are located on the surface of the substrate body  162 , and the graphene nanoribbons  22  are in direct contact with the substrate body  162 . Each graphene nanoribbon  22  is located between two adjacent protrusions  164  and extends between the two protrusions  164 , and the graphene nanoribbons  22  extend from one protrusion  164  to the adjacent protrusion  164 . The multiple graphene nanoribbons  22  are parallel to each other, and each graphene nanoribbon  22  has a ribbon structure or a one-dimensional linear structure. Furthermore, when the plurality of protrusions  164  are removed by etching, the graphene nanoribbon composite structure does not include the plurality of protrusions  164 , and is composed of the substrate body  162  and the plurality of graphene nanoribbons  22 . The material of the substrate  16  is the same as the material of the base  10 . In one embodiment, the plurality of graphene nanoribbons  22  extend along the same direction. 
     Referring to  FIG.  2   ,  FIG.  5   , and  FIG.  6   , a method for making the graphene nanoribbon composite structure  20  of the second embodiment, includes the following steps: 
     S 21 , providing the substrate  16  including the substrate body  162  and the plurality of protrusions  164  spaced apart from each other, wherein the plurality of protrusions  164  are located on the substrate body  162 ; 
     S 22 , growing the graphene film  13  on the growth substrate  11 ; 
     S 23 , locating the adhesive layer  15  on the surface of the graphene film  13  away from the growth substrate  11 ; 
     S 24 , removing the growth substrate  11 , and washing with water or organic solvent; 
     S 25 , taking the graphene film  13  and the adhesive layer  15  out of the water or the organic solution by using the substrate  16 , and drying, to obtain the first composite structure  17 , wherein the first composite structure  17  includes the substrate  16 , the graphene film  13 , and the adhesive layer  15 ; the graphene film  13  is located between the adhesive layer  15  and the substrate  16 , and the graphene film  13  is in direct contact with the protrusions  164 ; 
     S 26 , removing the adhesive layer  15  to obtain the second composite structure  19 , wherein the second composite structure  19  includes the substrate  16  and the graphene film  13 , the graphene film  13  is located on the surfaces of the protrusions  164  and the surface of the substrate body  162  between two adjacent protrusions  164 ; and the graphene film  13  forms the plurality of wrinkles  18  near the protrusions  164 , the wrinkles  18  are located on the surface of the substrate body  162  between the adjacent protrusions  164 , the wrinkles  18  extend along the Y direction, and the thickness of the graphene film  13  at the wrinkle  18  is greater than the thickness of the graphene film  13  on the surface of the substrate body  162  between adjacent protrusions  164 ; and 
     S 27 , etching from the surface of the graphene film  13  away from the substrate  16 , to remove the graphene films  13  on the protrusions  164  and the graphene film  13  on the surface of the substrate body  162  between the adjacent protrusions  164 , except for the wrinkles  18 , thereby obtaining the graphene nanoribbon composite structure  20 , wherein the graphene nanoribbon composite structure  20  includes the substrate body  162 , the plurality of protrusions  164 , and the plurality of graphene nanoribbons  22  parallel to each other; and the plurality of graphene nanoribbons  22  are spaced apart from each other and located on the substrate body  162 . 
     The method for making the graphene nanoribbon composite structure  20  in the second embodiment is similar to the method for making the graphene nanoribbon composite structure  20  in the first embodiment. In the second embodiment, the method for making the substrate  16  is not limited, as long as the substrate  16  includes the substrate body  162  and the plurality of protrusions  164  spaced apart from each other, and the plurality of protrusions  164  are located on the substrate body  162 . 
     Referring to  FIG.  2   ,  FIG.  5    and  FIG.  7   , a method for making the graphene nanoribbon composite structure  20  in a third embodiment, includes the following steps: 
     S 31 , providing the substrate  16  including the substrate body  162  and the plurality of protrusions  164  spaced apart from each other, wherein the plurality of protrusions  164  are located on the substrate body  162 ; 
     S 32 , dripping water or an organic solvent on the substrate body  162  between two adjacent protrusions  164  and the plurality of protrusions  164 ; 
     S 33 , locating the graphene film  13  on the surface of the substrate  16  and the protrusions  164  between the graphene film  13  and the substrate body  162 , and drying, so that the wrinkle  18  is formed near each protrusion  164 , wherein the wrinkles  18  are located on the surface of the substrate body  162  between two adjacent protrusions  164  and extends along the Y direction, and the thickness of the graphene film  13  at the wrinkle  18  is greater than the thickness of the graphene film  13  on the surface of the substrate body  162  between two adjacent protrusions  164 ; and 
     S 34 , etching from the surface of the graphene film  13  away from the substrate  16 , to remove the graphene films  13  on the protrusions  164  and the graphene film  13  on the surface of the substrate body  162  between the adjacent protrusions  164  except for the wrinkles  18 , thereby obtaining the graphene nanoribbon composite structure  20 , wherein the graphene nanoribbon composite structure  20  includes the substrate body  162 , the plurality of protrusions  164 , and the plurality of graphene nanoribbons  22  parallel to each other; and the plurality of graphene nanoribbons  22  are spaced apart from each other and located on the substrate body  162 . 
     During step S 32 , the method of dripping water or organic solvent on the surface of substrate  16  is not limited. The water or the organic solvent is dripped on the surface of the substrate body  162  between two adjacent protrusions  164  and the surface of the protrusion  164  by a dropper. In this way, during the drying process, as the water or organic solvent evaporates, a vacuum state is gradually formed between the graphene film  13  and the substrate  16 , and the graphene film  13  is thus closely attached to the substrate  16 . Since the plurality of protrusions  164  are on the substrate body  162 , the graphene film  13  cannot be smoothly attached to the substrate body  162 , therefore the wrinkles  18  are formed near the protrusions  164 . During step S 33 , before drying, the water or the organic solvent is between the graphene film  13  and the substrate  16 . 
     Furthermore, in the step S 33 , the graphene film  13  is located on the surface of the substrate  16  by using the adhesive layer  15 . The specific method for locating the graphene film  13  on the surface of the substrate  16  by using the adhesive layer  15  is as described in the second embodiment, which will not be repeated here. 
     The method for making the graphene nanoribbon composite structure  20  in the third embodiment is similar to the method for making the graphene nanoribbon composite structure  20  in the first embodiment. In the third embodiment, the method for making the substrate  16  is not limited, as long as the substrate  16  includes the substrate body  162  and the plurality of protrusions  164  spaced apart from each other, and the plurality of protrusions  164  are located on the substrate body  162 ; and before locating the graphene film  13  on the surface of the substrate  16 , it is necessary to drip the water or organic solvent on at least the protrusions  164 . 
     Referring to  FIG.  2   ,  FIG.  5   , and  FIG.  8   , a method for making the graphene nanoribbon composite structure  20  in a fourth embodiment, includes the following steps: 
     S 41 , providing the substrate  16  including the substrate body  162  and the plurality of protrusions  164  spaced apart from each other, wherein the plurality of protrusions  164  are located on the substrate body  162 ; 
     S 42 , locating the graphene film  13  on the surface of the substrate  16  and the protrusions  164  between the graphene film  13  and the substrate body  162  in a water or organic solvent environment, so that there is water or organic solvent between the substrate  16  and the graphene film  13 ; and then drying, so that the wrinkle  18  is formed near each protrusion  164 , wherein the wrinkles  18  are located on the surface of the substrate body  162  between two adjacent protrusions  164  and extends along the Y direction, and the thickness of the graphene film  13  at the wrinkle  18  is greater than the thickness of the graphene film  13  on the surface of the substrate body  162  between two adjacent protrusions  164 ; and 
     S 43 , etching from the surface of the graphene film  13  away from the substrate  16 , to remove the graphene films  13  on the protrusions  164  and the graphene film  13  on the surface of the substrate body  162  between the adjacent protrusions  164  except for the wrinkles  18 , thereby obtaining the graphene nanoribbon composite structure  20 , wherein the graphene nanoribbon composite structure  20  includes the substrate body  162 , the plurality of protrusions  164 , and the plurality of graphene nanoribbons  22  parallel to each other; and the plurality of graphene nanoribbons  22  are spaced apart from each other and located on the substrate body  162 . 
     Furthermore, in the step S 42 , the graphene film  13  is located on the surface of the substrate  16  by using the adhesive layer  15 . The specific method for making the graphene film  13  on the surface of the substrate  16  by using the adhesive layer  15  is as described in the second embodiment, and will not be repeated here. 
     The method for making the graphene nanoribbon composite structure  20  in the fourth embodiment is similar to the method for making the graphene nanoribbon composite structure  20  in the third embodiment. In the fourth embodiment, a graphene film  13  is located on the surface of the substrate  16  in an environment of water or organic solvent, and the protrusions  164  are located between the graphene film  13  and the substrate body  162 , there is water or organic solvent between the substrate  16  and the graphene film  13  before drying. Then, as the moisture or organic solvent evaporates, the wrinkles  18  formed by the graphene will be formed near the protrusions  164 . 
     Referring to  FIG.  9    and  FIG.  11   , a method for making a top-gate field effect transistor  100 , includes the following steps: 
     S 51 , providing the graphene nanoribbon composite structure  20  including the substrate  16  and the plurality of graphene nanoribbons  22  spaced apart from each other, wherein the plurality of graphene nanoribbons  22  are located on the substrate  16  and extend along the same direction, and each graphene nanoribbon  22  includes a first end and a second end opposite to the first end; 
     S 52 , forming a source electrode  102  on the first end of the graphene nanoribbon  22 , and forming a drain electrode  104  on the second end of the graphene nanoribbon  22 , wherein the source electrode  102  and the drain electrode  104  are electrically connected to the graphene nanoribbons  22 ; 
     S 53 , forming an insulating layer  106  on a surface of the graphene nanoribbons  22  away from the substrate  16 ; and 
     S 54 , forming a gate  108  on a surface of the insulating layer  106  away from the substrate  16 . 
     During step S 51 , the method for making the graphene nanoribbon composite structure  20  has been discussed in detail in the first embodiment to the fourth embodiment, and will not be repeated here. The plurality of graphene nanoribbons  22  are semiconductor layers of the field effect transistor  100 . The material of the substrate  16  is an insulating material, for example, P-type or N-type silicon with a certain thickness of oxide layer, transparent quartz, or transparent quartz with an oxide layer formed thereon. In addition, the insulating material may also be a resin, such as PET. 
     During step S 52 , in one embodiment, the source electrode  102  and the drain electrode  104  respectively cover the protrusion  164  and directly contact with the graphene nanoribbons  22 . The first end of the graphene nanoribbons  22  is in direct contact with the source  102 , and the second end of the graphene nanoribbons  22  is in direct contact with the drain  104 , as shown in  FIG.  10   . 
     The materials of the source  102  and the drain  104  have good conductivity. The material of the source electrode  102  and the drain electrode  104  may be metal, alloy, indium tin oxide (ITO), antimony tin oxide (ATO), conductive silver glue, conductive polymer, metallic carbon nanotube film, and so on. According to different types of materials for forming the source  102  and the drain  104 , different methods can be used to form the source  102  and the drain  104 . When the material of the source electrode  102  and the drain electrode  104  is metal, alloy, ITO or ATO, the source electrode  102  and the drain electrode  104  can be formed by evaporation, sputtering, deposition, masking, or etching. When the material of the source electrode  102  and the drain electrode  104  is conductive silver glue, conductive polymer or carbon nanotube film, the source electrode  102  and the drain electrode  104  can be formed by printing or direct laying the conductive silver glue or the carbon nanotube film. The thickness of the source electrode  102  and the drain electrode  104  is in a rang from about 0.5 nanometers to about 100 microns, and the distance between the source electrode  102  and the drain electrode  104  is in a range from about 10 nanometers to about 800 nanometers. In one embodiment, the material of the source  102  and the drain  104  is metal, the thickness of the source  102  and the drain  104  is about 50 nanometers, and the distance between the source  102  and the drain  104  is about 150 nanometers. 
     During step S 53 , the material of the insulating layer  106  may be hard materials such as silicon nitride and silicon oxide, or flexible materials such as benzocyclobutene (BCB), polyester, or acrylic resin. According to different types of materials of the insulating layer  106 , different methods can be used to form the insulating layer  106 . When the material of the insulating layer  106  is silicon nitride or silicon oxide, the insulating layer  106  can be formed by a deposition method. When the material of the insulating layer  106  is benzocyclobutene (BCB), polyester or acrylic resin, the insulating layer  106  can be formed by printing and coating. The thickness of the insulating layer  106  is in a range from about 0.5 nanometers to about 100 microns. In one embodiment, a deposition method is used to form a silicon nitride insulating layer  106 ; the silicon nitride insulating layer  106  covers the plurality of graphene nanoribbons  22 , the source  102 , and the drain  104 ; and the thickness of the insulating layer  106  is about 50 nanometers. 
     During step S 54 , the material of the gate  108  has good conductivity. The material of the gate  108  may be conductive materials such as metal, alloy, ITO, ATO, conductive silver glue, conductive polymer, and carbon nanotube film. The metal or alloy material may be aluminum, copper, tungsten, molybdenum, gold or their alloys. When the material of the gate  108  is metal, alloy, ITO or ATO, the gate  108  can be formed by methods such as evaporation, sputtering, deposition, masking, and etching. When the material of the gate  108  is conductive silver glue, conductive polymer or carbon nanotube film, the gate  108  can be formed by direct adhesion, printing, or coating. The thickness of the gate  108  is in a range from about 0.5 nanometers to about 100 microns. The gate  108  is electrically insulated from the plurality of graphene nanoribbons  22  by the insulating layer  106 . In one embodiment, the material of the gate  108  is aluminum, and the thickness of the gate  108  is about 50 nanometers. 
     Referring to  FIG.  11   , the field effect transistor  100  includes the graphene nanoribbon composite structure  20 , the source  102 , the drain  104 , the insulating layer  106  and the gate  108 . The source electrode  102  is located on the first end of the graphene nanoribbon  22 , and the drain electrode  104  is located on the second end of the graphene nanoribbon  22 . The source  102  and the drain  104  are electrically connected to the graphene nanoribbons  22 . In one embodiment, the source  102  and the drain  104  are in direct contact with the graphene nanoribbons  22 . The insulating layer  106  is located between the graphene nanoribbons  22  and the gate  108 , so that the graphene nanoribbons  22  and the gate  108  are electrically insulated. The source  102  and the gate  108  are electrically insulated by the insulating layer  106 . The drain  104  and the gate  108  are electrically insulated by the insulating layer  106 . 
     Referring to  FIG.  12    and  FIG.  13   , a method for making a bottom-gate field effect transistor  200 , includes the following steps: 
     S 61 , providing the graphene nanoribbon composite structure  20  including the substrate  16  and the plurality of graphene nanoribbons  22  spaced apart from each other, wherein the plurality of graphene nanoribbons  22  are located on the substrate  16  and extend along the same direction, and each graphene nanoribbon  22  includes a first end and a second end opposite to the first end; 
     S 62 , forming the source electrode  102  on the first end of the graphene nanoribbon  22 , and forming the drain electrode  104  on the second end of the graphene nanoribbon  22 , wherein the source electrode  102  and the drain electrode  104  are electrically connected to the graphene nanoribbons  22 ; and 
     S 63 , forming the gate  108  on a surface of the substrate  16  away from the graphene nanoribbons  22 . 
     During step S 61 , the material of the substrate  16  is an insulating material. During step S 63 , the graphene nanoribbons  22  and the gate  108  are respectively located on two opposite surfaces of the substrate  16 , and the substrate  16  is equivalent to the insulating layer of the field effect transistor  200 . When the substrate  16  is a silicon wafer with a certain thickness of silicon oxide, and the graphene nanoribbons  22  are in direct contact with the silicon oxide, the step S 63  can be omitted. In this case, the silicon wafer is equivalent to the gate of the field effect transistor  200  (silicon is conductive), and the silicon oxide is equivalent to the insulating layer of the field effect transistor  200  (silicon oxide is not conductive). In the process of preparing the graphene nanoribbon composite structure  20 , the substrate  10  is the silicon wafer with a certain thickness of silicon oxide, and the mask layer  12  is disposed on the silicon oxide, so that the silicon wafer substrate  16  with a certain thickness of silicon oxide can be obtained, and the graphene nanoribbons  22  are in direct contact with silicon oxide. 
     Referring to  FIG.  13   , the field effect transistor  200  includes the graphene nanoribbon composite structure  20 , the source  102 , the drain  104  and the gate  108 . The source electrode  102  is located on the first end of the graphene nanoribbon  22 , and the drain electrode  104  is located on the second end of the graphene nanoribbon  22 . The source  102  and the drain  104  are electrically connected to the graphene nanoribbons  22 . The material of the substrate  16  is the insulating material. In one embodiment, the source  102  and the drain  104  are in direct contact with the graphene nanoribbons  22 . The gate  108  is located on the surface of the substrate  16  away from the graphene nanoribbon composite structure  20 . 
     When the substrate  16  in the graphene nanoribbon composite structure  20  is the silicon wafer with the silicon oxide, and the graphene nanoribbons  22  are located on the silicon oxide, the gate  108  can be omitted. The silicon wafer can be used as the gate of the field effect transistor  200 , and the silicon oxide can be used as the insulating layer of the field effect transistor  200 . 
     The field effect transistor of the sixth embodiment is similar to the field effect transistor of the fifth embodiment, except that: the field effect transistor of the fifth embodiment is a top-gate field effect transistor, and the field effect transistor of the sixth embodiment is a bottom-gate field effect transistor. 
     Referring to  FIG.  14    and  FIG.  15   , a method for making a field effect transistor  300  in a seventh embodiment, includes the following steps: 
     S 71 , providing the graphene nanoribbon composite structure  20  including the substrate  16  and the plurality of graphene nanoribbons  22  spaced apart from each other, wherein the plurality of graphene nanoribbons  22  are located on the substrate  16  and extend along the same direction; and 
     S 72 , locating an interdigital electrode  210  on the surface of the graphene nanoribbon composite structure  20 , wherein the interdigital electrode  210  covers the plurality of protrusions  164  and is electrically connected to the graphene nanoribbons  22 . 
     During step S 71 , the substrate  16  of the graphene nanoribbon composite structure  20  is the silicon wafer with silicon oxide, and the graphene nanoribbons  22  are located on the silicon oxide and directly contact with the silicon oxide. 
     During step S 72 , in one embodiment, the interdigital electrode  210  is formed by two comb-teeth electrodes. The interdigital electrode  210  includes a first electrode  212  and a second electrode  214 . The first electrode  212  includes a plurality of first sub-electrodes  2120 , and the second electrode  214  includes a plurality of second sub-electrodes  2140 . The plurality of first sub-electrodes  2120  and the plurality of second sub-electrodes  2140  are spaced apart and alternately arranged on the surface of the graphene nanoribbon composite structure  20 . The plurality of first sub-electrodes  2120  and the plurality of second sub-electrodes  2140  cover the plurality of protrusions  164 , and electrically connected to the plurality of graphene nanoribbons  22 . The plurality of graphene nanoribbons  22  are between the substrate  16  and the interdigital electrode  210 . In one embodiment, the plurality of first sub-electrodes  2120  are in direct contact with the plurality of graphene nanoribbons  22 , and the plurality of second sub-electrodes  2140  are in direct contact with the plurality of graphene nanoribbons  22 . The extending directions of the plurality of first sub-electrodes  2120  are perpendicular to the extending directions of the plurality of graphene nanoribbons  22 , and the extending directions of the plurality of second sub-electrodes  2140  are perpendicular to the extending directions of the graphene nanoribbons  22 . The plurality of first sub-electrodes  2120  are electrically connected to each other, and the plurality of second sub-electrodes  2140  are electrically connected to each other. 
     In one embodiment, the plurality of first sub-electrodes  2120  are electrically connected through a connecting portion  2122 , and the plurality of second sub-electrodes  2140  are electrically connected through the connecting portion  2122 , as shown in  FIG.  15   . The connecting portion  2122  functions as an electrical connection, and is made of conductive material, such as metal. The connecting portion  2122  may be integrally formed with the plurality of first sub-electrodes  2120 , and the connecting portion  2122  may be integrally formed with the plurality of second sub-electrodes  2140 , to form the interdigital electrode  210 . The first electrode  212 , the second electrode  214 , the source electrode  102 , and the drain electrode  104  are made of the same material. 
     Referring to  FIG.  16   , the field effect transistor  300  includes the graphene nanoribbon composite structure  20  and the interdigital electrode  210 , and the interdigital electrode  210  is located on the graphene nanoribbon composite structure  20 . The interdigital electrode  210  is electrically connected to the graphene nanoribbons  22 . In one embodiment, the plurality of first sub-electrodes  2120  and the plurality of second sub-electrodes  2140  are spaced apart and alternately located on the surface of the graphene nanoribbon composite structure  20 , and the plurality of first sub-electrodes  2120  and the plurality of second sub-electrodes  2140  cover the plurality of protrusions  164 . The plurality of first sub-electrodes  2120  and the plurality of second sub-electrodes  2140  are in direct contact with the plurality of graphene nanoribbons  22 . The substrate  16  of the graphene nanoribbon composite structure  20  is the silicon wafer with silicon oxide, and the graphene nanoribbons  22  are located on the silicon oxide and directly contact the silicon oxide. The silicon wafer is used as the gate of the field effect transistor  300 , and silicon oxide is used as the insulating layer of the field effect transistor  300 . 
     The field effect transistors  100 ,  200 , and  300  and the methods for making the field effect transistors  100 ,  200 , and  300  have the following advantages: first, in the field effect transistors  100 ,  200 , and  300 , the semiconductor layer is the plurality of graphene nanoribbons  22 , before combining the graphene film  13  and the substrate  16 , water or organic solvent is located on the substrate  16 , so that the plurality of wrinkles  18  is formed near the protrusions  164  when combining the graphene film  13  and the substrate  16 ; and the plurality of graphene nanoribbons  22  is obtained by further etching the graphene film  13 ; second, the field effect transistors  100 ,  200 , and  300  can be prepared in a large area, and the cost and energy consumption are low. 
     The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including, the full extent established by the broad general meaning of the terms used in the claims. 
     Additionally, it is also to be understood that the above description and the claims drawn to a method may comprise some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.