ENHANCED GRAPHENE STRUCTURE BASED ON WEAK COUPLING, GRAPHENE FILM, AND PHOTOELECTRIC DEVICE

Abstract

A weakly coupled enhanced graphene film includes an enhanced graphene structure based on weak coupling, wherein the enhanced graphene structure based on weak coupling comprises a plurality of graphene units stacked vertically; the graphene unit is a single graphene sheet, or consists of two or more graphene sheets stacked in AB form; two vertically adjacent graphene units are weakly coupled, to promote the hot electron transition and increase the joint density of states, thereby increasing the number of hot electrons in high-energy states; the stacking direction of the graphene units in the graphene structure is in the thickness direction of the graphene film; and the graphene film enhances the accumulation of hot electrons in high-energy states by the enhanced graphene structure based on weak coupling.

Claims

1. A weakly coupled enhanced graphene film, comprising an enhanced graphene structure based on weak coupling, wherein the enhanced graphene structure based on weak coupling comprises a plurality of graphene units stacked vertically; the graphene unit is a single graphene sheet, or consists of two or more graphene sheets stacked in AB form; two vertically adjacent graphene units are weakly coupled, to promote the hot electron transition and increase the joint density of states, thereby increasing the number of hot electrons in high-energy states; the stacking direction of the graphene units in the graphene structure is in the thickness direction of the graphene film; and the graphene film enhances the accumulation of hot electrons in high-energy states by the enhanced graphene structure based on weak coupling.

2. The graphene film according to claim 1, wherein the graphene film has an I.sub.D/I.sub.G ratio of 0.05 or less.

3. The graphene film according to claim 1, wherein the graphene film has a non-AB structure content of 5% or more.

4. The graphene film according to claim 1, obtained by repairing, by thermal treatment, the defects in a graphene oxide film obtained by solution assembly, wherein the graphene oxide film having a thickness of 20 to 120 nm is deposited on a rigid substrate with a porosity of 60% or greater by solution assembly, and then peeled off from the rigid substrate through a process where the graphene oxide film is placed in a reduction chamber with HI vapor and chemically reduced until the graphene oxide film is automatically peeled off from the substrate, wherein the reduction process is continued for at least 10 min in an environment where the HI concentration is at least 0.3 g/L and the steam concentration is 0.07 g/L at most.

5. The graphene film according to claim 4, wherein in the process, an evaporation chamber connected to the reduction chamber is used to evaporate hydroiodic acid to feed HI vapor into the reduction chamber.

6. The graphene film according to claim 5, wherein the reduction chamber and the evaporation chamber are located in a same closed cavity, and the evaporation chamber is located below the reduction chamber; the evaporation chamber is located in an oil bath or a water bath at a temperature ranged from 80 to 120° C.; the reduction chamber has a condensation zone at the top, and the temperature in the condensation zone is ranged from 0 to 40° C.

7. The graphene film according to claim 6, wherein the condensation zone is provided with a water-absorbing material comprising a porous and strong water-absorbing material or a strong water-absorbing chemical, wherein the porous and strong water-absorbing material comprises at least one of water-absorbing filter paper and super absorbent resin, and the strong water-absorbing chemical comprises at least one of: calcium chloride and phosphorus pentoxide.

8. The graphene film according to claim 6, wherein a HI-resistant rack is provided in the reduction chamber for loading the substrate.

9. The graphene film according to claim 5, wherein the reduction chamber and the evaporation chamber are located in a same closed cavity; the two closed cavities are connected by a condenser tube; the temperature in the condenser tube is ranged from 0 to 40° C.; and the condenser tube condenses the steam evaporated in the evaporation chamber and returns the condensed water to the evaporation chamber.

10. The graphene film according to claim 9, wherein the evaporation chamber and the reduction chamber are both located in an oil bath or a water bath at a temperature ranged from 80 to 120° C., and the temperature of the reduction chamber is lower than that of the evaporation chamber.

11. The graphene film according to claim 4, wherein the substrate is anodic aluminum oxide, a tetrafluoroethylene filter membrane, or a glass fiber filter membrane,

12. The graphene film according to claim 1, obtained by stacking, layer-by-layer, graphene films grown by CVD, and then thermally treating to form a dense structure.

13. The graphene film according to claim 1, obtained by solution assembly of a graphitizable material and thermal treatment to graphitize the graphitizable material.

14. The graphene film according to claim 13, wherein the graphitizable material is selected from a group consisting of graphene oxide, polyimide, and a mixture of graphene oxide with a non-graphitizable or low-graphitizable polymer.

15. The graphene film according to claim 1, obtained from glass-transition small molecules under the catalysis of a nickel-based catalyst.

16. A graphene photoelectric device, comprising a weakly coupled enhanced graphene film according to claim 1 and a semiconductor substrate, wherein the weakly coupled enhanced graphene film is spread on the semiconductor substrate.

17. The graphene photoelectric device according to claim 16, wherein the graphene film is spread on the semiconductor substrate by placing the graphene film on the semiconductor substrate, and dripping a solvent of high surface tension on the edge of the graphene film, so that the solvent spreads out the wrinkles of the graphene film when the solvent penetrates from the edge of the graphene film to the inside, and volatilizing the solvent.

18. The graphene photoelectric device according to claim 16, wherein the solvent of high surface tension comprises one or more of the following: deionized water, dmf, dmac, ethylene glycol, propylene glycol, o-xylene, toluene, butyl acetate, liquid paraffin, Menthol and a mixture thereof.

19. The graphene photoelectric device according to claim 16, wherein after the solvent is volatilized, the graphene film is further sintered at a sintering temperature of 400 to 1000 degrees Celsius.

20. The graphene photoelectric device according to claim 16, wherein the semiconductor substrate comprises: an elemental semiconductor or a compound semiconductor, including one or more of the following: Si, Ge, diamond, Sn, InP, GaAs, AlGaAs, InGaP, InGaAs, AlInGaP, AlInGaAs, InGaAsP, AlInGaAsP, GaN, InGaN, AlGaN, AlInGaN, GaP, alloys and derivatives thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 is an xps spectrum of two graphene films prepared in Example 1.

[0041] FIG. 2 is a Raman spectrum of two graphene films prepared in Example 1.

[0042] FIG. 3 is an TEM image of two graphene films prepared in Example 1.

[0043] FIG. 4 is an electron diffraction pattern of two graphene films prepared in Example 1.

[0044] FIG. 5 shows the relaxation time of hot electrons of two graphene films prepared in Example 1.

[0045] FIG. 6 shows an electron diffraction pattern and corresponding electron lifetime after treatments at different temperature.

[0046] FIG. 7 shows the principle underlying the superposition of light absorption of a multilayer graphene by weak coupling.

[0047] FIG. 8 shows a gradual separation process of a graphene film from a substrate.

[0048] FIG. 9 shows a graphene oxide film (4 inches) obtained by suction filtration on a rigid anodic aluminum oxide filter membrane.

[0049] FIG. 10A1 shows a separated graphene oxide film (4 inches), in which a graphene nanofilm transferred with the aid of a solid phase transfer agent is shown.

[0050] FIG. 10A2 is an enlarged view of FIG. 10A1.

[0051] FIG. 10B1 shows a separated graphene oxide film (4 inches), in which a graphene nanofilm without damages prepared by the transfer agent-free method of the present application according to Examples 2 is shown.

[0052] FIG. 10B2 is an enlarged view of FIG. 10B1.

[0053] FIG. 10C1 shows a separated graphene oxide film (4 inches), in which a graphene nanofilm without damages prepared by the transfer agent-free method of the present application according to Examples 3 is shown.

[0054] FIG. 10C2 is an enlarged view of FIG. 10C1.

[0055] FIG. 10D1 shows a separated graphene oxide film (4 inches), in which a graphene nanofilm without damages prepared by the transfer agent-free method of the present application according to Examples 4 is shown.

[0056] FIG. 10D2 is an enlarged view of FIG. 10D1.

[0057] FIG. 11A shows a schematic plan view of a separation apparatus in Example 2.

[0058] FIG. 11B shows a schematic perspective view B of a separation apparatus in Example 2.

[0059] FIG. 12 shows a view of a separation apparatus in Example 3.

[0060] FIG. 13 shows a view of a separation apparatus in Example 4.

DESCRIPTION OF THE EMBODIMENTS

[0061] The following description is intended to disclose the present disclosure so that those skilled in the art can accomplish the present disclosure. The preferred embodiments in the following description are only exemplary, and other obvious variations easily occur to those skilled in the art. The basic principles of the present disclosure defined in the following description are applicable to other embodiments, variations, improvements, equivalents, and other technical solutions without departing from the spirit and scope of the present disclosure.

[0062] In the following examples, the I.sub.D/I.sub.G is tested as follows. A film is transferred to a silicon substrate, and tested over a full-wave band by Raman spectroscopy using 532-nm laser as a light source at a full power. A Raman spectrum containing a D peak, a G peak and a 2D peak is obtained. The areas of the D peak and the G peak are respectively defined as the intensity I.sub.D and I.sub.G of the D peak and the G peak, and I.sub.D/I.sub.G is obtained by a division operation.

[0063] In the following examples, the test method of the AB structure content is as described in: Measuring the degree of stacking order in graphite by Raman spectroscopy, Carbon, 2008, 46(2), 272-275.

[0064] Single-layer graphene or multi-layer AB-stacked graphene exhibits a set of diffraction patterns consisting of 6 diffraction spots (evenly distributed on the same circumference). Moreover, as the number of AB-stacked graphene layer increases, the brightness of the spots increases. The existence of non-AB structure causes the occurrence of multiple sets of non-overlapping spots in the diffraction pattern. Based on this, in the following examples, the prepared film is placed under a high-resolution TEM to collect the electron diffraction pattern, and the vertically stacked structure can be tested according to the diffraction pattern. On the one hand, the number of structural units in the film can be calculated by the sets of diffraction spots; on the other hand, the stacked layers of each structural unit can be estimated by the ratio of the brightness of the diffraction spots to the diffraction brightness of a single layer of graphene.

[0065] The weak coupling effect described in the present disclosure refers to the coupling effect of electron cloud caused by the disordered stacking of graphene sheets. In this case, the electron cloud between the sheets does not achieve a complete coupling effect, and the intersheet spacing is 0.334-0.36 nm. For the AB-stacked structure, the orbit coupling strength of electron cloud between the graphene sheets is the largest, and the intersheet spacing is 0.334 nm; and this is a strong coupling effect.

[0066] In the present disclosure, the graphene unit is a single graphene sheet, or consists of 2-9 stacked graphene sheets. The number of graphene units in the vertical direction in the graphene film can be obtained by measuring the total thickness of the graphene film and dividing the thickness by the thickness of single-layer graphene. Moreover, the number of graphene sheets in a single graphene unit can be calculated by determining the AB structure content by Raman spectroscopy and averaging.

Example 1: Calculation of Enhancement by Weak Coupling

[0067] In this example, thin films with the same thickness were prepared, and the influence of the structure transformation of graphene films on the relaxation time of hot electrons and photoelectric detection were determined under the premise that the defects were ≈0. The preparation method was as follows:

[0068] Graphene film of non-AB structure: The graphene oxide was spin-coated to prepare a 24 nm-thick film, and heated to 2000° C. for 16 hrs at a ramping rate of 10° C. per minute. The content of non-AB structure is ≈100%, the number of graphene structural units in the vertical direction is 30, and the number of graphene sheet in a single graphene structural unit is 1.

[0069] Graphene film of AB structure: The graphene oxide was spin-coated to prepare a 24 nm-thick film, and heated to 2800° C. for 2 hrs at a ramping rate of 10° C. per minute.

[0070] As shown in FIG. 1, after high-temperature sintering, the oxygen atoms in the two materials are completely removed, and no signal peaks of O are detected in the XPS spectrum. On this basis, the sp3 structure content and stacking form of the film were characterized by Raman spectroscopy in the present application. As shown in FIG. 2, no D peaks are observed for the two films, indicating that no sp3 structures exist in the two film; and the 2D peaks have obvious differences, the 2D peak of the film with high content of AB structure has high asymmetry.

[0071] The test results by TEM are in complete agreement with the test results by Raman spectroscopy. FIG. 3 shows an electron diffraction pattern of the graphene film with AB structure. This graphene film is stacked with only two structural units, and the spot brightness of one structural unit is significantly higher than that of the second structural unit. That is to say, one of the two structural units is extremely thick, and the other one has very few atomic layers, and the two are stacked on each other in non-AB form. The graphene film of non-AB structure has more sets of diffraction spots (FIG. 4), which even forms an amorphous diffraction ring, indicating that this film consists of a large number of structural units stacked on top of each other in non-AB form.

[0072] Based on the above structure, the relaxation time of hot electrons of the two film is tested in the present application. As shown in FIG. 5, with the same excitation time of 200 fs, the relaxation time of hot electrons of the graphene film with AB structure reaches 25 ps, and the relaxation time of hot electrons of the graphene film with non-AB structure is maintained within 10 ps. It can be seen that the graphene units are weakly coupled, and their structure much resembles single-sheet graphene units, which increases the joint density of states and thus increases the number of hot electrons in high-energy states.

[0073] The two graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0074] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0075] (2) The graphene film was spread on the working window and in contact with the electrode layer. Ethylene glycol was dripped to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0076] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0077] A reverse bias voltage of −2V to −1V (where the silicon terminal was grounded) was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown in Table 1.

TABLE-US-00001 TABLE 1 Graphene film of non-AB Graphene film of AB Test Item structure structure Irradiate the graphene layer with A 600 μA photocurrent A 98 μA photocurrent infrared light having a wavelength signal is measured within 20 ns signal is measured within 20 ns of 1 μm and a power of 5 mW Irradiate the graphene layer with A 35 μA photocurrent signal A 4 μA photocurrent signal infrared light having a wavelength is measured within 25 ns is measured within 25 ns of 4 μm and a power of 20 mW Irradiate the graphene layer with A 2.5 μA photocurrent A 1.1 μA photocurrent infrared light having a wavelength signal is measured within 80 ns signal is measured within 80 ns of 10.6 μm and a power of 50 mW

Example 2

[0078] Step 1: The graphene oxide obtained by the hummer method was prepared into a graphene oxide aqueous solution with a concentration of 0.5 μg/mL. Then the graphene oxide aqueous solution was suction filtered to form a graphene oxide film having a thickness of 100 nm and an area of 80±5 cm.sup.2 on a rigid tetrafluoroethylene filter membrane with a porosity of 60% as a substrate.

[0079] In this example, an apparatus as shown in FIGS. 11A and B was used to peel off the graphene oxide film. The apparatus includes a cylindrical cavity 3 containing a hydroiodic acid solution 2, a PTFE net rack 2 fixed above the liquid surface of the hydroiodic acid solution, a top cover 4 for sealing the cylindrical cavity, and a water-absorbing filter paper 5 provided on the top cover.

[0080] A lower part of the cylindrical cavity was located in a water bath 1 at 80° C., and a sample to be peeled was placed on the PTFE net rack 2.

[0081] The hydroiodic acid solution was evaporated by heating into HI vapor and steam. The steam was condensed on the top and absorbed by the water-absorbing filter paper, so the steam content in the cavity was reduced. Whereas, the condensation temperature of HI was lower, and it remained gaseous.

[0082] In this embodiment, the cylindrical cavity 3 has a volume of 1 L and a bottom area of 120 cm.sup.2. The mass concentration of the hydroiodic acid solution in the cavity 3 was 50%, the weight content of HI was 0.42 g, and the rest was water (0.42 g). The water absorption limit of the water-absorbing filter paper (2 g) was 60% of its weight. The ambient temperature of the upper part of the cavity 3 was 0° C.

[0083] After heating for 5 min, the hydroiodic acid solution 2 was completely evaporated, and the contained hydrogen iodide solution became invisible to the naked eyes. On the top layer, some condensed water droplets were observed, and the water-absorbing filter paper expanded after moisture absorption. The water-absorbing filter paper was sampled and tested to gain 0.44 g in weight. At this time, the gas was sampled and tested for the acidity, and the concentration of hydroiodic acid was found to remain at 0.33 g/L. It was proved that the steam content in the cavity 3 is below 0.07 g/L. After 1 h, the gas was sampled and tested for the acidity again, and the concentration of hydroiodic acid was found to still remain at 0.32 g/L.

[0084] In order to avoid the influence of the above-mentioned sampling and test on the graphene film, a same device was additionally provided in this example, where no water-absorbing filter paper (2 g) and gas in the cavity were sampled, and a same graphene oxide film was directly peeled off. The treatment time was 4 hrs, and the graphene was peeled off after 4 hrs, as shown in FIGS. 10B1 and B2. It can be seen from the figure that by the reduction with hydroiodic acid, the graphene film is completely separated from the substrate under stress, and there is no occurrence of macroscopic damage or microscopic holes in the separation process.

[0085] 3 graphene films were prepared following the method in Step 1.

[0086] Step 2: The three sample films were respectively annealed in a graphitization furnace at 1600° C., 1800° C., and 2000° C. for 2 hrs.

[0087] The films were tested by Raman spectroscopy. The I.sub.D/I.sub.G and non-AB structure content are shown in Table 2.

[0088] As shown in A1-A3 in FIG. 6, the test of vertically stacked structure by TEM and electron diffraction and the same analysis as in Example 1 confirm that the three graphene films contain a large number of weakly coupled graphene structures including a plurality of graphene units stacked vertically, where the graphene unit is formed by irregularly stacking single-sheet graphene and two vertically adjacent graphene units are weakly coupled.

[0089] With an excitation time of 200 fs, the relaxation times of hot electrons of the graphene film are shown in B1-B3 in FIG. 6, and they are all not less than 5 ps.

[0090] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0091] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0092] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent to obtain an independent photoelectric device.

[0093] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0094] A reverse bias voltage of −2V to −1V (where the silicon terminal was grounded) was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown in Table 2.

TABLE-US-00002 TABLE 2 Graphitization Graphitization furnace annealing at furnace annealing Graphitization furnace Test Item 1600° C. at 1800° C. annealing at 2000° C. I.sub.D/I.sub.G 0.23 0.08 0.005 Non-AB structure content ≈100% ≈100% ≈100% Number of graphene ≈200    ≈200    ≈200    structural units in the vertical direction Number of graphene ≈1 ≈1 ≈1 sheets in the structural unit Irradiate the graphene A 1.54 mA A 1.58 mA A 1.6 mA layer with infrared light photocurrent signal photocurrent signal photocurrent signal is having a wavelength of 1 is measured within is measured within measured within 20 ns μm and a power of 5 mW 52 ns 31 ns Irradiate the graphene A 155 μA A 161 μA A 164 mA layer with infrared light photocurrent signal photocurrent signal photocurrent signal is having a wavelength of 4 is measured within is measured within measured within 18 ns μm and a power of 20 mW 18 ns 18 ns Irradiate the graphene A 10.7 μA A 11.2 μA A 12 μA photocurrent layer with infrared light photocurrent signal photocurrent signal signal is measured having a wavelength of is measured within is measured within within 20 ns 10.6 μm and a power of 20 ns 20 ns 50 mW

Example 3

[0095] (1) The graphene oxide obtained by the hummer method was prepared into a graphene oxide aqueous solution with a concentration of 0.5 μg/mL. Then the graphene oxide aqueous solution was suction filtered to form a graphene oxide film having a thickness of 60 nm and an area of 80±5 cm.sup.2 on a rigid anodic aluminum oxide filter membrane with a porosity of 80% as a substrate.

[0096] In this example, the device as shown in FIG. 12 was used to peel off the graphene oxide film. The device includes a left cavity 11 and a right cavity 12. The cavities 11 and 12 communicate with each other through an inclined condenser tube 13. Both cavities 11 and 12 were placed in a water bath 14 at 80° C.

[0097] The cavity 11 contained a hydroiodic acid solution, and the cavity 12 was used to hold the graphene oxide film to be stripped. The hydroiodic acid solution in the cavity 11 was volatilized. The steam therein was condensed in the condenser tube and returned to the cavity 11. The condensation temperature of HI was relatively high, and it was fed to the cavity 12 through the condenser tube 13, to create an environment of high HI concentration and low steam concentration in the cavity 12.

[0098] In this example, the volume of the cavities 11 and 12 is 400 mL, and the bottom area is 50 cm.sup.2. The content of the hydroiodic acid solution in the cavity 11 was 0.5 g (the mass concentration of HI was 55%). The ambient temperature of the condenser tube 13 was 40° C., the length of the condenser tube was 20 cm, and the inclination angle was 30 degrees. These can effectively ensure the creation of an environment of high HI concentration and low steam concentration in the cavity 12.

[0099] Experiments have proved that after heating for 5 min, the hydroiodic acid solution was completely evaporated, and the steam was condensed and returned to the cavity 11 in a front part of the condenser tube. No condensed water was produced in a rear part of the condenser tube, indicating that almost no steam enters the reduction room at the right side. The gas in the reduction chamber was sampled and tested for the acidity, and the concentration of hydroiodic acid was found to still remain at 0.43 g/L.

[0100] After 30 min, evaporation-condensation reflux was kept in the evaporation chamber, and there was still no condensed water in the rear part of the condenser tube. The gas in the reduction chamber was sampled and tested for the acidity, and the concentration of hydroiodic acid was found to still remain at 0.41 g/L.

[0101] In order to avoid the influence of the above-mentioned sampling and test on the graphene film, a same device was additionally provided in this example, where no gas in the cavity was sampled, and a same graphene oxide film was directly peeled off. After 1 hr of reduction, the graphene film was peeled off, as shown in FIGS. 10C1 and C2. It can be seen from the figure that by the reduction with hydroiodic acid, the graphene film is completely separated from the substrate under stress, and there is no occurrence of macroscopic damage or microscopic holes in the separation process.

[0102] (2) The film was annealed for 0.5 hr in a graphitization furnace at 2000° C.

[0103] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is 0.05, the content of non-AB structure is ≈100%, the number of graphene structural units in the vertical direction is 60, and the number of graphene sheet in a single graphene structural unit is 1.

[0104] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of weakly coupled graphene structures including a plurality of graphene units stacked vertically, where the graphene unit is formed by irregularly stacking single-sheet graphene, and two vertically adjacent graphene units are weakly coupled.

[0105] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0106] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0107] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0108] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0109] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0110] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 1.1 mA was measured within 20 ns.

[0111] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 97 μA was measured within 25 ns.

[0112] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 8.3 μA was measured within 80 ns.

Example 4

[0113] (1) The graphene oxide obtained by the hummer method was prepared into a graphene oxide aqueous solution with a concentration of 0.5 μg/mL. Then the graphene oxide aqueous solution was suction filtered to form a graphene oxide film having a thickness of 60 nm and an area of 80±5 cm.sup.2 on a rigid anodic aluminum oxide filter membrane with a porosity of 80% as a substrate.

[0114] In this example, the device as shown in FIG. 13 was used to peel off the graphene oxide film. The device includes a left cavity 11 and a right cavity 12. The cavities 11 and 12 communicate with each other through an inclined condenser tube 13. The cavity 11 was placed in an oil bath 14 at 120° C., and the cavity 12 was placed in a water bath 14 at 80° C.

[0115] The cavity 11 contained a hydroiodic acid solution, and the cavity 12 was used to hold the graphene oxide film to be stripped. The hydroiodic acid solution in the cavity 11 was volatilized. The steam therein was condensed in the condenser tube and returned to the cavity 11. The condensation temperature of HI was relatively high, and it was fed to the cavity 12 through the condenser tube 13, to create an environment in the cavity 12 with high HI concentration and low steam concentration.

[0116] As described in Example 2, in this example, the volume of the cavities 11 and 12 is 400 mL, and the bottom area is 50 cm.sup.2. The content of the hydroiodic acid solution in the cavity 11 was 0.3 g (the mass concentration of HI was 55%). The ambient temperature of the condenser tube 13 was 20° C., the length of the condenser tube was 20 cm, and the inclination angle was 30 degrees. These can effectively ensure the creation of an environment of high HI concentration and low steam concentration in the cavity 12.

[0117] Experiments have proved that after heating for 5 min, the hydroiodic acid solution was completely evaporated, and the steam was condensed and returned to the cavity 11 in a front part of the condenser tube. No condensed water was produced in a rear part of the condenser tube, indicating that almost no steam enters the reduction room at the right side. The gas in the reduction chamber was sampled and tested for the acidity, and the concentration of hydroiodic acid was found to still remain at 0.33 g/L.

[0118] After 10 min, evaporation-condensation reflux was kept in the evaporation chamber, and there was still no condensed water in the rear part of the condenser tube. The gas in the reduction chamber was sampled and tested for the acidity, and the concentration of hydroiodic acid was found to still remain at 0.30 g/L.

[0119] In order to avoid the influence of the above-mentioned sampling and test on the graphene film, a same device was additionally provided in this example, where no gas in the cavity was sampled, and a same graphene oxide film was directly peeled off. After 2 hrs of reduction, the graphene film was peeled off, as shown in FIGS. 10D1 and D2. It can be seen from the figure that by the reduction with hydroiodic acid, the graphene film is completely separated from the substrate under stress, and there is no occurrence of macroscopic damage or microscopic holes in the separation process.

[0120] (2) The film was annealed for 12 hrs in a graphitization furnace at 2000° C.

[0121] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is 0.003, the content of non-AB structure is ≈100%, the number of graphene structural units in the vertical direction is 60, and the number of graphene sheet in a single graphene structural unit is 1.

[0122] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of weakly coupled graphene structures including a plurality of graphene units stacked vertically, where the graphene unit is formed by irregularly stacking single-sheet graphene, and two vertically adjacent graphene units are weakly coupled.

[0123] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0124] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0125] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0126] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0127] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0128] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 1.13 mA was measured within 20 ns.

[0129] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 99 μA was measured within 25 ns.

[0130] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 8.1 μA was measured within 80 ns.

Example 5

[0131] (1) The graphene oxide obtained by the hummer method was prepared into a graphene oxide aqueous solution with a concentration of 0.5 μg/mL. Then the graphene oxide aqueous solution was suction filtered to form a graphene oxide film on anodic aluminum oxide as a substrate, where the number of atomic layers of graphene oxide is 120.

[0132] In this example, an existing solid-phase transfer agent was used to finely transfer a graphene oxide film deposited on anodic aluminum oxide and an intact independent self-supporting film was obtained after many attempts.

[0133] (2) The film was annealed for 4 hrs in a graphitization furnace at 2300° C.

[0134] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0 (below the detection limit of Raman spectroscopy), the content of AB structure is 50%, the number of graphene structural units in the vertical direction is 60, and the number of graphene sheet in a single graphene structural unit is 2.

[0135] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of weakly coupled graphene structures including a plurality of graphene units stacked vertically, where the graphene unit is formed by irregularly stacking single-sheet graphene, and two vertically adjacent graphene units are weakly coupled.

[0136] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0137] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0138] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0139] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0140] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0141] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 1.3 mA was measured within 20 ns.

[0142] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 122 mA was measured within 25 ns.

[0143] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 10 μA was measured within 80 ns.

Example 6

[0144] (1) The graphene oxide obtained by the hummer method was prepared into a graphene oxide aqueous solution with a concentration of 0.5 μg/mL. Then the graphene oxide aqueous solution was suction filtered to form a graphene oxide film on anodic aluminum oxide as a substrate, where the number of atomic layers of graphene oxide is 120.

[0145] In this example, an existing solid-phase transfer agent was used to finely transfer a graphene oxide film deposited on anodic aluminum oxide and an intact independent self-supporting film was obtained after many attempts.

[0146] (2) The film was annealed for 2 hrs in a graphitization furnace at 2800° C.

[0147] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0, the content of AB structure is 90%, the number of graphene structural units in the vertical direction is 13, and the number of graphene sheet in a single graphene structural unit is 9.

[0148] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form, and two vertically adjacent graphene units are weakly coupled.

[0149] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0150] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0151] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0152] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0153] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0154] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 1.1 mA was measured within 20 ns.

[0155] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 113 μA was measured within 25 ns.

[0156] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 9 μA was measured within 80 ns.

Example 7

[0157] (1) A single-layer graphene on copper prepared by CVD was removed from the substrate by the hydrogen evolution method, and stacked layer by layer until the number of atomic layers of graphene is 150.

[0158] (2) The film was annealed for 12 hrs in a graphitization furnace at 2000° C.

[0159] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is 0.003, the content of non-AB structure is ≈100%, the number of graphene structural units in the vertical direction is 150, and the number of graphene sheet in a single graphene structural unit is 1.

[0160] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of weakly coupled graphene structures including a plurality of graphene units stacked vertically, where the graphene unit is formed by irregularly stacking single-sheet graphene, and two vertically adjacent graphene units are weakly coupled.

[0161] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0162] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0163] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0164] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0165] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0166] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 4 mA was measured within 20 ns.

[0167] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 160 μA was measured within 25 ns.

[0168] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 15 μA was measured within 80 ns.

Example 8

[0169] (1) A single-layer graphene on copper prepared by CVD was removed from the substrate by the hydrogen evolution method, and stacked layer by layer until the number of atomic layers of graphene is 150.

[0170] (2) The film was annealed for 2 hrs in a graphitization furnace at 2800° C.

[0171] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0, the content of AB structure is ≈50%, the number of graphene structural units in the vertical direction is 75, and the number of graphene sheet in a single graphene structural unit is 2.

[0172] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form, and two vertically adjacent graphene units are weakly coupled.

[0173] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0174] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0175] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0176] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0177] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0178] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 3.3 mA was measured within 20 ns.

[0179] The graphene layer with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 130 μA was measured within 18 ns.

[0180] The graphene layer with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 14 μA was measured within 20 ns.

Example 9

[0181] (1) A multi-layer graphene on nickel prepared by CVD was removed from the substrate by etching with hydrochloric acid and hydrogen peroxide and stacked layer by layer until the number of atomic layers of graphene is 180.

[0182] (2) The film was annealed for 12 hrs in a graphitization furnace at 2000° C.

[0183] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is 0.003, the content of non-AB structure is 50%, the number of graphene structural units in the vertical direction is 90, and the number of graphene sheet in a single graphene structural unit is 2.

[0184] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of weakly coupled graphene structures including a plurality of graphene units stacked vertically, where the graphene unit is formed by irregularly stacking single-sheet graphene, and two vertically adjacent graphene units are weakly coupled.

[0185] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0186] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0187] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0188] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0189] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0190] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0191] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 5.0 mA was measured within 20 ns.

[0192] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 190 μA was measured within 25 ns.

[0193] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 17 μA was measured within 80 ns.

Example 10

[0194] (1) A multi-layer graphene on nickel prepared by CVD was removed from the substrate by etching with hydrochloric acid and hydrogen peroxide and stacked layer by layer until the number of atomic layers of graphene is 180.

[0195] (2) The film was annealed for 2 hrs in a graphitization furnace at 2800° C.

[0196] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0, the content of AB structure is 89%, the number of graphene structural units in the vertical direction is 60, and the number of graphene sheet in a single graphene structural unit is 3.

[0197] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form, and two vertically adjacent graphene units are weakly coupled.

[0198] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0199] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0200] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0201] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0202] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0203] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 4.1 mA was measured within 20 ns.

[0204] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 120 μA was measured within 25 ns.

[0205] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 11 μA was measured within 80 ns.

Example 11

[0206] (1) A multi-layer graphene on nickel prepared by CVD was removed from the substrate by etching with hydrochloric acid and hydrogen peroxide and stacked alternately layer-by-layer with a single-layer graphene prepared on a copper substrate, until the number of atomic layers of graphene is 180.

[0207] (2) The film was annealed for 2 hrs in a graphitization furnace at 2800° C.

[0208] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0, the content of AB structure is 75%, the number of graphene structural units in the vertical direction is 60, and the number of graphene sheet in a single graphene structural unit is 3.

[0209] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form, and two vertically adjacent graphene units are weakly coupled.

[0210] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0211] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0212] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0213] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0214] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0215] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 4.4 mA was measured within 20 ns.

[0216] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 130 μA was measured within 25 ns.

[0217] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 14 μA was measured within 80 ns.

Example 12

[0218] (1) A polyimide solution was spin-coated on a multilayer graphene on nickel prepared by CVD, and a polyimide/graphene composite film with a total thickness of 100 nm was obtained. The substrate was removed by etching with hydrochloric acid and hydrogen peroxide.

[0219] (2) The film was annealed for 2 hrs in a graphitization furnace at 2800° C.

[0220] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0, the content of AB structure is 90%, the number of graphene structural units in the vertical direction is 14, and the number of graphene sheet in a single graphene structural unit is 9.

[0221] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form, and two vertically adjacent graphene units are weakly coupled.

[0222] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0223] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0224] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0225] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0226] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data obtained is shown.

[0227] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 0.91 mA was measured within 20 ns.

[0228] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 97 μA was measured within 25 ns.

[0229] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 7.3 μA was measured within 80 ns.

Example 13

[0230] (1) Polyacrylonitrile with a thickness of 100 nm was spin coated on a single-layer graphene on copper prepared by CVD, and then the substrate was removed by the hydrogen evolution method.

[0231] (2) The film was annealed for 12 hrs in a graphitization furnace at 2300° C.

[0232] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is 0.04, the content of non-AB structure is 50%, the number of graphene structural units in the vertical direction is 60, and the number of graphene sheet in a single graphene structural unit is 2.

[0233] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form, and two vertically adjacent graphene units are weakly coupled.

[0234] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0235] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0236] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0237] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0238] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data was obtained.

[0239] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 1.21 mA was measured within 20 ns.

[0240] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 35 μA was measured within 25 ns.

[0241] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 9.2 μA was measured within 80 ns.

Example 14

[0242] (1) A single-layer graphene was formed on the surface of anodic aluminum oxide by suction filtration, and then a mixture of pitch and graphene oxide (at a weight ratio of 1:1) with a thickness of 200 nm was formed by suction filtration. The substrate was removed by camphor transfer.

[0243] (2) The film was annealed for 2 hrs in a graphitization furnace at 2800° C.

[0244] The film was tested by Raman spectroscopy. I.sub.D/I.sub.G is ≈0, the content of AB structure is 95%, the number of graphene structural units in the vertical direction is 8, and the number of graphene sheet in a single graphene structural unit is 19.

[0245] The test of vertically stacked structure by TEM and electron diffraction confirms that the graphene film contains a large number of strongly coupled graphene structures including a small number of graphene units stacked vertically, where the graphene unit is formed by stacking single-sheet graphene in AB form and two vertically adjacent graphene units are weakly coupled.

[0246] The graphene films prepared above were used to fabricate a photoelectric device according to the following steps:

[0247] (1) A working window was reserved on a Si substrate, an insulating layer was coated in other areas than the working window, and then a Pt electrode layer was sputtered in the insulating layer.

[0248] (2) The graphene film was spread flatly on the working window and in contact with the electrode layer. Ethylene glycol was added dropwise to the edge of the graphene film to allow ethylene glycol to penetrate from the edge of the graphene film to the inside. The solvent was volatilized, and the film was tightly bound to the semiconductor by virtue of the surface tension of the solvent, to obtain an independent photoelectric device.

[0249] (3) The photoelectric device was encapsulated, and a lead wire is respectively connected to the electrode layer and the semiconductor substrate of the photoelectric device for outputting detection signals.

[0250] A reverse bias voltage of −2V to −1V was applied between the electrode and the semiconductor of the device by a Keithley source meter, and then the device was connected to an amplifier circuit and then to an oscilloscope. The test data was obtained.

[0251] The graphene layer was irradiated with infrared light having a wavelength of 1 μm and a power of 5 mW, and a photocurrent signal of 3.1 mA was measured within 20 ns.

[0252] The graphene layer was irradiated with infrared light having a wavelength of 4 μm and a power of 20 mW, and a photocurrent signal of 112 μA was measured within 25 ns.

[0253] The graphene layer was irradiated with infrared light having a wavelength of 10.6 μm and a power of 50 mW, and a photocurrent signal of 12.5 μA was measured within 80 ns.