Background
With the rapid development of electronic and communication technologies, the connection between commercial portable electronic products (such as tablet computers, smart phones, etc.) and people's daily life is becoming more and more tight. The development of modern big data, cloud computing, communication and electronic product applications put flexible, miniaturized, intelligent and highly integrated application demands on the development of electronic components. However, for the trend toward miniaturized, high density transistors and integrated circuit devices, the increase in computing power is often at the expense of increased device and chip heat dissipation, which can result in dramatic reductions in product performance and reliability.
The core process for realizing the flexibility of the device is to print a semiconductor functional film on a flexible substrate such as plastic or metal foil, and the like, wherein the currently adopted flexible substrate is mostly a high polymer substrates (polymer substrates), Ultra-thin glass (Ultra-thin glass), Ultra-thin metal (Ultra-thin metal), flexible mica sheets and the like. However, the chemical stability and thermal stability of the high molecular polymer substrate are poor; ultra-thin glass is expensive; when the electronic device based on the ultrathin metal works normally, the thermal diffusion to the functional material can occur, so that the performance of the device is directly influenced; although the flexible mica sheet can resist certain high temperature and has certain chemical stability, the mica has high brittleness and can not realize full flexibility.
Therefore, it is urgently needed to find a flexible multifunctional substrate material which is cheap and has ultrahigh electrical conductivity and thermal conductivity and excellent flexibility and is applied to next-generation portable electronic devices and wearable devices.
Graphene as a single atomic layer thick carbon atom in sp2In the form of honeycomb lattice two-dimensional nano material bonded togetherThe material has excellent properties such as high current density, ballistic transport, chemical inertness, high thermal conductivity, and superhydrophobicity. Graphene, a single layer of carbon atoms bonded in a hexagonal lattice, is an ultra-thin material possessing excellent electrical and thermal conductivity and a resistivity of only 10-8Omega cm, conductivity of about 106S·m-1Therefore, graphene has become one of the most pyrogenic materials studied in recent years.
Graphene is a layered two-dimensional material, and if the graphene is directly combined with an electrode, the interfacial bonding force is poor, and an electrode layer is easy to fall off. CN108486568B adopts a large-scale graphene film as a substrate, and a layer of metal copper is compounded on the surface of the graphene film, so that a composite film with good electrical conductivity, thermal conductivity and flexibility is prepared. However, due to the chemical inertness of graphene, other materials such as metallic titanium are difficult to realize tight combination with graphene, which also limits the practical application of graphene in the field of substrates.
Therefore, the problem of interface bonding between a large graphene sheet and a functionalized thin film is solved, and the graphene flexible substrate material is ensured to have comprehensive properties such as excellent flexibility, bending resistance, electrical conductivity, thermal conductivity, high temperature resistance and the like, so that the problem to be solved is needed at present.
Disclosure of Invention
In view of the problems in the prior art, an object of the present invention is to provide a large-area graphene-based flexible substrate and a method for manufacturing the same, so as to solve the technical problem of how to use graphene as a substrate in a large area and how to combine the bottom surface of graphene with other materials, thereby manufacturing a graphene-based flexible substrate with excellent overall properties such as flexibility, bending resistance, electrical conductivity, thermal conductivity, and high temperature resistance.
In order to solve the technical problems, the invention provides a large-area graphene-based flexible substrate, which comprises structures arranged from bottom to top in sequence: big piece graphite alkene layer, buffer layer, go up intercalation, upper electrode. The large graphene layer can be used as a flexible substrate material in a large area, the buffer layer and the upper intercalation layer are made of corresponding metal materials, so that the bonding force between the two layers is stronger, specifically, metal silver is used as the buffer layer, and metal titanium is used as the upper intercalation layer. Because titanium cannot be directly combined with graphene, metal silver is required to be used as a buffer layer, and the graphene and the titanium can form a very stable eutectic body with a good combination state through silver at high temperature, so that the titanium, the silver and the graphene sheets are sequentially and tightly anchored together; the metal titanium is used as an upper intercalation layer, and other functionalized upper electrodes can be prepared on the upper intercalation layer due to the strong activity of the metal titanium.
Further, the buffer layer is made of metal silver; the upper intercalation material is metallic titanium; the upper electrode material includes all commonly commercialized metals, conductive metal oxides, and the like.
Further, the thickness of the buffer layer material is 500nm-1 μm.
Further, the thickness of the upper intercalation material is 30-150 nm.
The invention also provides a preparation method of the large-area graphene-based flexible substrate, which comprises the following steps:
step 1, preparing a large-area graphene flexible film to obtain a large graphene layer;
step 2, preparing a silver (Ag) buffer layer on the large graphene layer by adopting a magnetron sputtering or vacuum evaporation method;
step 3, preparing a titanium (Ti) upper intercalation layer on the silver (Ag) buffer layer by adopting a magnetron sputtering or vacuum evaporation method to obtain a primary large-area graphene flexible substrate;
and 4, sintering the primary large-area graphene flexible substrate prepared by the method to obtain the large-area graphene flexible substrate.
Further, when the magnetron sputtering method is adopted to prepare the Ag buffer layer in the step 2, the sputtering power is 90-110w, the pressure is 0.1-0.5Pa, the substrate temperature is room temperature, and the sputtering time is 900-.
Further, when the magnetron sputtering method is adopted to prepare the Ti upper intercalation layer in the step 3, the sputtering power is 90-110w, the pressure is 0.1-0.5Pa, the substrate temperature is room temperature, and the sputtering time is 100-3000 s.
Further, after the intercalation is performed on the prepared Ti in the step 3, a functionalized upper electrode layer can be prepared on the Ti by adopting a magnetron sputtering or vacuum evaporation method, so that the functionalized primary large-area graphene flexible substrate is obtained.
Further, the magnetron sputtering method is adopted to prepare the functionalized upper electrode layer, the sputtering power is 90-110w, the pressure is 0.1-0.5Pa, the substrate temperature is room temperature, and the sputtering time is 100-3000 s.
Further, in step 4, the primary flexible substrate is sintered at a temperature of 1000 ℃ to 1500 ℃ and under a pressure of 0.01 to 0.001 atmosphere.
The high vacuum is used in the step 4 to prevent oxidation of titanium.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the large-area graphene-based flexible substrate, a large-area graphene film is used as the substrate, Ag is used as a buffer layer, and Ti is used as an upper intercalation layer, so that titanium, silver and graphene sheets are tightly anchored together in sequence, and other functionalized upper electrodes can be further prepared on the upper intercalation layer;
(2) compared with a common functional material substrate, the conductivity of the large-area graphene-based flexible substrate can reach 4.28 multiplied by 106~5.23×106S/m, thermal conductivity up to 1484-2014 Wm-1K-1;
(3) The large-area graphene-based flexible substrate has excellent flexibility and bending resistance, and can resist temperature of more than 1500 ℃;
(4) the thickness of the large-area graphene-based flexible substrate can be adjusted correspondingly according to practical application, the requirements of the flexible substrate on electrical conductivity, thermal conductivity and functional film process adaptability can be met, the large-area graphene-based flexible substrate is wide in application fields, such as electronic devices, microprocessors, flexible wearable devices, corrosion resistance fields and the like, and the large-area graphene-based flexible substrate can be used as a heat conduction material of high-power and high-integration systems such as LED illumination, computers, satellite circuits, laser weapons, handheld terminal equipment and the like;
(5) the preparation method provided by the invention is simple and feasible, has low operation cost, and is beneficial to commercial popularization.
Detailed Description
The technical solutions in the embodiments of the present invention are described in detail below with reference to the drawings in the patent embodiments of the present invention. It should be understood that the embodiment described in this embodiment is merely a general case of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step other than that described in the claims, are within the scope of protection of the present invention.
Example 1
A Pt/Ag/large-area graphene composite flexible substrate is prepared by the following steps:
1. preparation of large graphene flexible film
A suspension of commercial graphene oxide was diluted with ultrapure water having a resistivity of 18.25 M.OMEGA.cm to a concentration of 1mg/mL and centrifuged. The bottom 20% volume solution was diluted to 1mg/mL and centrifuged again for the next cycle. Repeating the above operation 7 times, taking the last solution with the volume of 20% at the bottom, concentrating the solution into graphene oxide gel with the volume of 10mg/mL, coating the graphene oxide gel on the surface of the PET film by blade, drying the film for 24 hours in vacuum, forming a large graphene oxide film on the PET film, and separating the large graphene oxide film from the PET film.
The large graphene oxide film is placed in a graphite high-temperature furnace, carbonized for 5 hours at 1300 ℃ in an inert argon atmosphere, and then thermally treated for 2 hours at 2800 ℃. And after cooling, further heating and rolling at 300 ℃ for forming to obtain the large graphene flexible film.
2. Preparation of buffer layer
And depositing metal silver on the prepared large graphene flexible film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 100w, the pressure is 0.3Pa, the substrate temperature is room temperature, the sputtering time is 900-1200s, the thickness of the silver layer is controlled to be 500-800 nm, and annealing is carried out for 50min to prepare the Ag/large graphene composite film.
3. Preparation of the Upper intercalation layer
Depositing metal titanium on the prepared Ag/large graphene composite film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 100w, the pressure is 0.3Pa, the substrate temperature is room temperature, the sputtering time is 100-3000s, the thickness of a titanium layer is controlled to be 30-150nm, and annealing is carried out for 50min to prepare the Ti/Ag/large graphene composite film.
4. Preparation of the Upper electrode
Depositing metal platinum (Pt) on the prepared Ti/Ag/large graphene composite film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 90-110w, the pressure is 0.1-0.5Pa, the substrate temperature is room temperature, the sputtering time is 100-3000s, and the thickness of the Pt layer is controlled at 100-300nm to prepare the Pt/Ag/large graphene composite film.
5. Sintering
The Pt/Ag/large graphene composite film is placed in a graphite high-temperature furnace and sintered for 6 hours at the temperature of 1200 ℃ under high vacuum (0.001 atmospheric pressure), and the large-area graphene-based flexible substrate is successfully prepared.
Example 2
An ITO/Ag/large-area graphene composite flexible substrate is prepared by the following steps:
1. preparation of large graphene flexible film
A suspension of commercial graphene oxide was diluted with ultrapure water having a resistivity of 18.25 M.OMEGA.cm to a concentration of 2mg/mL and centrifuged. The bottom 30% volume solution was diluted to 2mg/mL and centrifuged again for the next cycle. Repeating the above operation 7 times, taking the final solution with the volume of 30% at the bottom, concentrating into graphene oxide gel with the volume of 20mg/mL, coating on the surface of the PET film by blade, vacuum drying for 24 hours, forming a large graphene oxide film on the PET film, and separating the large graphene oxide film from the PET film.
Placing a large graphene oxide film in a graphite high-temperature furnace, firstly carbonizing at 1200 ℃ for 2 hours in an inert argon atmosphere, and then carrying out heat treatment at 3000 ℃ for 1 hour. And after cooling, further heating and rolling at 200 ℃ for forming to obtain the large graphene flexible film.
2. Preparation of buffer layer
And depositing metal silver on the prepared large graphene flexible film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 100w, the pressure is 0.3Pa, the substrate temperature is room temperature, the sputtering time is 900-1200s, the thickness of the silver layer is controlled to be 500-800 nm, and annealing is carried out for 30min to prepare the Ag/large graphene composite film.
3. Preparation of the Upper intercalation layer
Depositing metal titanium on the prepared Ag/large graphene composite film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 100w, the pressure is 0.3Pa, the substrate temperature is room temperature, the sputtering time is 100-3000s, the thickness of a titanium layer is controlled to be 30-150nm, and annealing is carried out for 30min to prepare the Ti/Ag/large graphene composite film.
4. Preparation of the Upper electrode
And depositing Indium Tin Oxide (ITO) on the prepared Ti/Ag/large graphene composite film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 90-110w, the pressure is 0.1-0.5Pa, the substrate temperature is room temperature, the sputtering time is 100-3000s, and the thickness of the ITO layer is controlled to be 100-300nm to prepare the ITO/Ag/large graphene composite film.
5. Sintering
The ITO/Ag/large graphene composite film is placed in a graphite high-temperature furnace and sintered for 3 hours at the temperature of 1100 ℃ in high vacuum (0.005 atmospheric pressure), and the large-area graphene-based flexible substrate is successfully prepared.
Example 3
An FTO/Ag/large-area graphene composite flexible substrate is prepared by the following steps:
1. preparation of large graphene flexible film
A suspension of commercial graphene oxide was diluted with ultrapure water having a resistivity of 18.25 M.OMEGA.cm to a concentration of 5mg/mL and centrifuged. The bottom 10% volume solution was diluted to 5mg/mL and centrifuged again for the next cycle. Repeating the above operation 7 times, taking the final solution with the bottom 10% volume, concentrating into 50mg/mL graphene oxide gel, coating on the surface of a PET film by blade, vacuum drying for 24 hours, forming a large graphene oxide film on the PET film, and separating the large graphene oxide film from the PET film.
The large graphene oxide film is placed in a graphite high-temperature furnace, carbonized for 3 hours at the temperature of 1100 ℃ in an inert argon atmosphere, and then thermally treated for 0.5 hour at the temperature of 3500 ℃. And after cooling, further heating and rolling at 300 ℃ for forming to obtain the large graphene flexible film.
2. Preparation of buffer layer
And depositing metal silver on the prepared large graphene flexible film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 100w, the pressure is 0.3Pa, the substrate temperature is room temperature, the sputtering time is 900-1200s, the thickness of the silver layer is controlled to be 500-800 nm, and annealing is carried out for 40min to prepare the Ag/large graphene composite film.
3. Preparation of the Upper intercalation layer
And depositing titanium on the prepared Ag/large graphene composite film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 100w, the pressure is 0.3Pa, the substrate temperature is room temperature, the sputtering time is 100-3000s, the thickness of the titanium layer is controlled to be 30-150nm, and annealing is carried out for 30min to prepare the Ti/Ag/large graphene composite film.
4. Preparation of the Upper electrode
And (3) depositing FTO (fluorine-doped tin dioxide) on the prepared Ti/Ag/large graphene composite film by using a magnetron sputtering method, wherein in the deposition process, the sputtering power is 90-110w, the pressure is 0.1-0.5Pa, the substrate temperature is room temperature, the sputtering time is 100-3000s, and the thickness of the FTO layer is controlled to be 100-300nm, so that the FTO/Ag/large graphene composite film is prepared.
5. Sintering
Placing the FTO/Ag/large graphene composite film in a graphite high-temperature furnace, sintering for 4 hours at the temperature of 1200 ℃ in high vacuum (0.01 atmospheric pressure), and successfully preparing the large-area graphene-based flexible substrate.
Testing one: atomic force scan analysis
Atomic force scanning analysis is respectively carried out on the large graphene flexible film prepared in the step 1 of the embodiment 1 and the large-area graphene-based flexible substrate prepared in the embodiment 1, and fig. 2 and fig. 3 are obtained, and it can be seen from the figures that the large graphene flexible film related to fig. 2 has a rough surface and cannot be directly used as a device substrate; the large-area graphene-based flexible substrate surface related to fig. 3 achieves atomic-level flatness and can be used as a graphene-based flexible substrate for depositing other functional films.
And (2) testing: cross section scan analysis
The cross section scanning analysis of the large-area graphene-based flexible substrate prepared in example 1 is performed to obtain a graph 4, and it can be known from the graph that the upper intercalation layer has an obvious phenomenon of diffusion towards graphene, and the layers of the large-area graphene-based flexible substrate are tightly combined.
And (3) testing: other Performance tests
After the Ti/Ag/large graphene composite films prepared in the above examples 1 to 3 were respectively sintered, the electrical conductivity, the conductivity retention rate after 200 times of bending, the thermal conductivity, the flexibility (tested using the flexible test platform shown in fig. 5), and other properties were tested, and the test results are shown in table 1.
TABLE 1 test results of Ti/Ag/Large graphene composite films fabricated in examples 1-3
The table shows that the large-area graphene flexible substrate provided by the invention has excellent comprehensive properties such as flexibility, bending resistance, electrical conductivity, thermal conductivity and high temperature resistance.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.