CN112941476B

CN112941476B - Tin dioxide/copper/tin dioxide multilayer transparent conductive film and preparation method and application thereof

Info

Publication number: CN112941476B
Application number: CN202110120008.1A
Authority: CN
Inventors: 宋安刚; 霍方方; 胡俊华; 朱地; 赵保峰; 关海滨; 徐丹; 王树元
Original assignee: Energy Research Institute of Shandong Academy of Sciences
Current assignee: Shandong Chanyan New Energy Technology Co.,Ltd.
Priority date: 2021-01-28
Filing date: 2021-01-28
Publication date: 2022-09-16
Anticipated expiration: 2041-01-28
Also published as: CN112941476A

Abstract

The invention discloses a tin dioxide/copper/tin dioxide multilayer transparent conductive film, a preparation method and application thereof.

Description

Tin dioxide/copper/tin dioxide multilayer transparent conductive film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of novel transparent conductive oxide films, and particularly relates to a tin dioxide/copper/tin dioxide multilayer transparent conductive film, and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

Transparent conductive oxide thin films (TCOs) have been widely used in optoelectronic devices, particularly flat panel displays, light emitting diodes, touch panels, thin film solar cells, energy saving glass screens, and the like. In order for the film to be both transparent and conductive, the film must have a large forbidden bandwidth to avoid electrons from transiting from the valence band to the conduction band under visible light illumination, as this would create inter-band absorption. The thin film preferably also has impurity levels near the conduction or valence band so that electrons or holes are excited to the conduction or valence band by external factors and electrons move to form a current under the action of an applied electric field. In order to maintain good visible light transmittance, a broadband transparent conductive oxide semiconductor needs to have a plasma frequency lower than a visible light frequency, and needs to have a carrier concentration proportional to a plasma frequency in order to maintain a certain conductivity.

The development of transparent conductive films is based on how to make the two better organic. Since the first discovery that both light transmittance and conductivity can coexist in a transparent conductive oxide, the development of a novel TCO and the design of a composite multilayer film have been conducted around such a pair of lances. The TCO can control a band gap structure, carrier concentration and mobility, a work function, and the like by component adjustment to unify contradictions between light transmittance and conductivity. The single metal film has poor light transmission, so that the application of the single metal film is limited, and therefore, the single metal film and a dielectric medium with high refractive index are often formed into a composite multilayer film, so that the conductivity of metal and the light transmission of an antireflection film are organically unified, and the later developed composite of the TCO with high refractive index and the metal also obtains good matching of the light transmission and the conductivity. According to different materials, the early researches can divide the materials into a metal transparent conductive film, an oxide transparent conductive film (TCO), a non-oxide transparent conductive film and a polymer transparent conductive film.

Currently, the mainstream TCO thin film material mainly includes Indium Tin Oxide (ITO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), and the like. The tin oxide-based film material is a TCO film which is put into commercial use earlier, and compared with other film materials, the tin oxide-based film material has the advantages of lower price, higher chemical stability and acid corrosion resistance; high thermal stability and better mechanical performance. The tin oxide-based film is an N-type semiconductor material with wide forbidden band, the forbidden band width is between 3.5eV and 4eV, the crystal structures of the doped tin oxide and the undoped tin oxide are both tetragonal rutile type, and the unit cell of the film is a bodyRight-centered parallelepipeds. The tin oxide crystal in the ideal state has a full valence band structure with no conduction holes and a full conduction band structure with no free electrons providing carriers, so the tin oxide crystal in the ideal state is non-conductive. However, in practice, because the tin atoms and the oxygen atoms in the crystal lattice can deviate from the set positions due to the thermal shock caused by the thermal fluctuation of the material, the displacement of the tin atoms and the vacancy of the oxygen atoms are easily generated, and the formation of the oxygen vacancy can cause the film material to generate a certain amount of current carriers, so that the material has conductivity. The intrinsic tin oxide has poor conductivity, and the conductivity of the intrinsic tin oxide film can be greatly improved by properly doping the intrinsic tin oxide film. When fluorine is doped into the intrinsic tin oxide film, F ^- Will replace O ^2- Or forming interstitial fluorine atoms on the basis of the original tin oxide crystal structure, thereby obviously increasing the carrier concentration in the thin film and greatly improving the conductivity of the tin oxide thin film.

However, the stability of the FTO film in plasma is poor, the textured surface of the FTO film is not easy to corrode, and the FTO film can only be prepared on a large scale by using a high-temperature online Chemical Vapor Deposition (CVD) method in production practice. Chemical vapor deposition is a method in which one or more compounds or elemental gases containing elements constituting a thin film are supplied to a substrate or a base plate, and the compound or the elemental gas reacts with the substrate or the base plate via a vapor phase reaction to form a thin film on the surface of the substrate or the base plate. The process is less flexible, many gas phase precursors suitable for forming film layer materials are lacking or expensive, and practical production applications are limited. In addition, the conductivity of the existing FTO film is poor, and has a certain difference compared with other transparent conductive oxide films, and the requirement of practical application cannot be met. In addition, most of the transparent conductive films in commercial use require high deposition temperature or post annealing treatment to achieve the desired photoelectric properties, which results in complicated process and high cost. It is also difficult to prepare transparent conductive films on flexible substrates (such as PET or PEN) that cannot withstand high temperatures.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides a tin dioxide/copper/tin dioxide multilayer transparent conductive film and a preparation method and application thereof.

To solve the above technical problem, one or more of the following embodiments of the present invention provide the following technical solutions:

in a first aspect, the invention provides a tin dioxide/copper/tin dioxide multilayer transparent conductive film, which comprises a first tin dioxide film, a copper film and a second tin dioxide film which are sequentially overlapped, wherein the thickness of the copper film is less than 10nm, and the thickness of the tin dioxide film is 50-150 nm.

In a second aspect, the invention provides a preparation method of the tin dioxide/copper/tin dioxide multilayer transparent conductive film, which comprises the following steps:

and sputtering a first tin dioxide film, a copper film and a second tin dioxide film on the substrate in sequence by taking argon as a plasma gas source and oxygen as a reaction gas, wherein the tin dioxide film is deposited by reactive sputtering by adopting a remote source plasma sputtering technology, and the copper film is deposited by sputtering by adopting a direct current sputtering method.

In a third aspect, the invention provides an application of the tin dioxide/copper/tin dioxide multilayer transparent conductive film in the fields of flat panel displays, solar cells, microwave shielding and protective glasses and sensors.

Compared with the prior art, one or more technical schemes of the invention have the following beneficial effects:

the tin dioxide film prepared by the method is amorphous, generally, the conductivity of the amorphous film is poor, and the amorphous film prepared by the method has excellent conductivity.

In addition, by adopting the method, the sputtering preparation temperature is low, so that the transparent conductive film can be prepared on the flexible substrate, and further, the flexible conductive film can be applied to flexible electronic devices such as flexible display screens, and the application field of the transparent conductive film can be widened.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of a remote source plasma sputtering system used in an embodiment;

FIG. 2 is an X-ray diffraction pattern of the as-deposited tin dioxide/copper/tin dioxide transparent conductive film prepared in example 1 at different thicknesses of the intermediate copper film;

FIG. 3 is a Scanning Electron Microscope (SEM) chromatogram of the tin dioxide/copper/tin dioxide transparent conductive film of example 2 at different magnifications;

FIG. 4 is a graph showing the results of measuring the visible light transmittance of the tin dioxide/copper/tin dioxide transparent conductive film comprising examples 1, 2 and 3 at different thicknesses of the copper film in the intermediate layer;

FIG. 5 is a graph showing Hall electrical properties of as-deposited tin dioxide/copper/tin dioxide transparent conductive films comprising examples 1, 2 and 3 at different thicknesses of the intermediate copper film;

FIG. 6 shows the results of current-voltage curve measurements for different thicknesses of the as-deposited tin dioxide/copper/tin dioxide transparent conductive films of examples 1, 2 and 3 in the intermediate copper film;

figure 7 is an X-ray diffraction pattern of a pure tin dioxide film after annealing at 450 c.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In some embodiments, the copper film has a thickness of 1-10 nm.

In some embodiments, the first tin oxide film has a thickness of 90-110nm and the second tin oxide film has a thickness of 90-110 nm.

The preparation method of the tin dioxide/copper/tin dioxide transparent conductive film adopts a far-source plasma sputtering technology to perform direct-current sputtering deposition on a substrate to form a film, controls the oxygen flow and sputtering power in the reactive sputtering process, and controls the thickness of the middle-layer copper film to regulate and control the photoelectric property of the transparent conductive film under the conditions of relatively low sputtering power and oxygen flow.

According to the tin dioxide/copper/tin dioxide transparent conductive film and the preparation method thereof, the reactive sputtering deposition is carried out on the substrate by adopting a far-source plasma sputtering technology, the sputtering speed is high, the sputtering temperature is low, the repeatability is good, the obtained film has high light transmittance and low resistivity, the photoelectric property is excellent, and the tin dioxide/copper/tin dioxide transparent conductive film is suitable for popularization and application.

Far-source plasma sputtering comprises direct-current sputtering and radio-frequency sputtering, and tin dioxide is prepared by direct-current reactive sputtering, so that the direct-current sputtering is adopted because the direct-current sputtering has higher power, higher sputtering rate, more defects in a film and better conductivity.

The remote source plasma sputtering technique (HiTUS) is a sputtering technique with high target utilization rate, which accomplishes sputtering by high-density plasma generated remotely from the target. In The prior art, a Plasma emission System (PLS) is fixed on a sidewall of a vacuum chamber (sputtering chamber) of a remote Plasma sputtering System corresponding to The remote Plasma sputtering System, that is, a radio frequency coil antenna is wound outside a quartz glass tube; plasma is generated and amplified by an emission electromagnetic coil at the outlet of PLS, and the focusing and control of the direction of the plasma are completed by a beam-bunching electromagnetic coil. By fine control of the current to each solenoid, the plasma beam can be directed so as to cover the entire surface of the target. Under the condition, the argon ions on the surface of the target are in low energy (30-50 eV) and high density (ion number is 10) ¹² ～10 ¹⁴ /cm ³ ) Status. Therefore, the target material is uniformly etched, the target poisoning phenomenon is greatly reduced compared with the conventional magnetron sputtering, and the deposition rate of the sputtering deposition film is greatly improved.

The energy of the plasma beam on the target is about 10eV, the particles bombarded by the plasma beam on the target cannot be directly sputtered on the substrate with a certain distance, but stay and suspend near the surface of the target, and a proper accelerating voltage needs to be applied to the charged ions to enable the charged ions to fly to the surface of the substrate. The reactive sputtering in the step 1) is to continuously introduce oxygen as a reaction gas in the sputtering process, combine the oxygen with sputtered target particles in the air and react with the sputtered target particles, fly to the substrate in the form of a reaction product under the action of an accelerating bias voltage provided for the bottom of the target and adhere to the surface of the substrate, and deposit to form a layer of compact nano film.

In some embodiments, the substrate is a glass or flexible substrate. SnO ₂ The base film and the glass substrate have good adhesiveness, and the glass substrate can improve the bonding force between the film and the substrate and has good stability.

Further, the temperature of the substrate is 20-30 ℃ during the sputtering process. The process of reactive sputtering deposition of the film is carried out at normal temperature or lower temperature, the substrate does not need to be heated, and the sputtering process is simpler and easy to control.

Further, before use, the substrate is sequentially placed in acetone, isopropyl acetone, ethanol and deionized water for ultrasonic cleaning, the cleaning time is 15-25min each time, and the cleaning temperature is 45-55 ℃.

And cleaning, airing or wiping by using a dust-free cloth, putting into a sputtering cavity of a remote source plasma sputtering system, and preparing for sputtering.

Before reactive sputtering, the sputtering cavity is vacuumized to 9 x 10 ^-6 mbar. Then argon gas with a certain flow is introduced into the cavity, and oxygen is introduced after the pressure in the cavity is kept stable. The argon and oxygen are high-purity gases with the purity of not less than 99.999 percent.

In some embodiments, the argon flow is 60-80sccm and the pressure in the sputtering chamber is 3.7X 10 during reactive sputtering ^-3 -4.0×10 ^-3 mbar. And after oxygen is introduced into the chamber and the air pressure in the chamber and the voltage of the target material are stabilized, starting to perform reactive sputtering deposition on the film.

Further, the flow rate of oxygen is 1-10sccm when the tin dioxide thin film is prepared by reactive sputtering, the power of the plasma emission source is 500-1200W, the power of the target accelerating bias is 100-300W, and the sputtering time of the tin dioxide is 2-15 min.

Furthermore, the time of DC sputtering the copper film is 0-135s, not including 0s, and the thickness of the copper film is 1-10 nm.

Furthermore, in the reactive sputtering process, the sputtering temperature is 20-50 ℃. The process of reactive sputtering deposition of the film is carried out at normal temperature or lower temperature, the substrate does not need to be heated, and the sputtering process is simpler and easy to control.

In some embodiments, the purity of the tin and copper targets is 4N-5N.

In some embodiments, the method further comprises the step of pre-sputtering the target before reactively sputter depositing the thin film, wherein the bias voltage applied to the target is increased from a low level to a high level until the target bias power is increased.

Further, the initial bias voltage applied to the target is 40-60W, and the incremental value is 40-60W.

The target material can generate heat in the sputtering process, the target material generates excessive heat and generates expansion and contraction due to cold by directly applying too high bias voltage to the target material, and even the target material is possibly cracked and scrapped.

Example 1

The remote source plasma sputtering system is mainly composed of a plasma source emission system 1, a vacuum system, a plasma bunching electromagnet, a substrate sample holder 3, a target accelerating bias power supply, a reaction gas circuit 4, a water cooling system, an air compressor and the like, as shown in fig. 1. The vacuum system is composed of a vacuum chamber 9, a mechanical pump and a molecular pump, when the system is vacuumized, the mechanical pump is required to be firstly used for pumping to a certain vacuum degree, then the molecular pump is started, the molecular pump is used for directly pumping the gas in the vacuum chamber, the mechanical pump pumps the molecular pump when the molecular pump works, the two vacuum pumps transmit the gas in the vacuum chamber 9 to be pumped to the atmosphere, and therefore a high vacuum degree in the chamber can be guaranteed.

As shown in fig. 1, the left side of the vacuum chamber 9 is connected to the plasma source emission system 1; the plasma source emission system 1 is composed of a radio frequency antenna coil 2 and a quartz tube 10, wherein the radio frequency antenna coil 2 is uniformly wound on the periphery of the quartz tube 10 and has a certain uniform distance from the quartz tube 10. When plasma needs to be generated, high-purity argon gas with a certain flow is continuously introduced into the vacuum chamber 9, so that the air pressure in the chamber is stabilized at a required pressure, then the radio frequency antenna coil 2 is electrified, and under the action of a high-frequency radio frequency power supply, electrons and neutral particles in the quartz tube 10 keep a high collision rate, so that argon gas molecules are ionized, and light purple plasma can be generated in the quartz tube 10.

An electromagnet 5 for controlling the shape and the moving direction of the plasma beam, called a plasma bunching electromagnet coil, is respectively installed on one side of the quartz tube 10 of the plasma source emission system 1 close to the vacuum chamber 9 and below the target 6. Before the rf power is turned on to generate the plasma, the electromagnet 5 on the side of the vacuum chamber is activated to generate the desired magnetic field line distribution, so that the plasma generated by the plasma source is continuously delivered to the vacuum chamber 9. When the electromagnet 5 below the target does not work, the generated plasma is dispersedly distributed in the whole vacuum chamber 9, when the electromagnet 5 is electrified and generates a magnetic field, the shape of magnetic lines of force in the effective area is changed, the plasma moves along the magnetic lines of force according to the guiding action of the magnetic field, and the plasma is changed into a uniform light beam as a whole and is bent along with the magnetic field and directly and intensively hit the surface of the target 6. The shape of the magnetic lines of force is precisely controlled by adjusting the two electromagnets 5 to appropriate currents, so that the plasma beam can be guided to cover exactly the entire area of the target 6. As the plasma is applied to the surface of the target material, the target material 6 can generate more heat, in order to protect the target material and prevent the target material from being melted, circulating water 7 continuously flows in the copper plate 8 below the target material to take away the heat, and the circulating water 7 is radiated by an external water cooling machine and is kept at the level of room temperature.

The substrate sample holder is used for fixing a substrate, and an openable or closable baffle plate is arranged below the substrate sample holder and is used for being tightly attached to the lower surface of the substrate so as to control the beginning or the end of reactive sputtering deposition on the surface of the substrate.

The target material used is pure metal, and the size of the target material is 3 inches in diameter and 6mm in thickness.

The preparation method of the tin dioxide/copper/tin dioxide transparent conductive film comprises the following steps:

1) cleaning a substrate: sequentially putting the glass substrate into acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning, wherein the cleaning time is 20min each time, and the cleaning temperature is 50 ℃; taking out the substrate after ultrasonic cleaning, wiping the substrate clean by using a dust-free cloth, and finally putting the substrate into a sputtering cavity of a remote source plasma sputtering system for sputtering;

2) sputtering: the method takes argon as a plasma gas source, oxygen as a reaction gas, and adopts a remote source plasma sputtering technology to perform reactive sputtering deposition on a glass substrate to form a film, and specifically comprises the following steps:

before reactive sputtering, the sputtering chamber of the far-source plasma sputtering system is vacuumized to 9 x 10 ^-6 mbar, introducing argon of 70sccm into the chamber, and starting a plasma source emission system after the pressure in the chamber is kept stable so as to generate plasma at the plasma source; starting a plasma bunching electromagnet to enable the target to be bombarded by the plasma, and pre-sputtering the target;

introducing oxygen into the chamber, wherein the flow rate of the oxygen is 3.0sccm, and the pressure in the sputtering chamber is 3.7 multiplied by 10 ^-3 mbar, wherein the used argon and oxygen are high-purity gases with the purity of not less than 99.999%; after the air pressure in the chamber and the voltage of the target material are stabilized, opening a baffle plate tightly attached to the lower part of the glass substrate, and starting to perform reactive sputtering deposition on the film;

in the reactive sputtering process, the power of a plasma emission source is 600W, the accelerating bias power of a target material is 100W, the sputtering speed is 4.5nm/min, the reactive sputtering time of the upper layer of tin dioxide and the lower layer of tin dioxide is 3min, the thickness of a copper film is 4nm, the sputtering temperature is 20 ℃, and the substrate temperature is normal temperature;

and after the sputtering is finished, closing the baffle below the glass substrate, depositing a layer of nano film on the glass substrate to obtain a finished product, and naturally cooling to room temperature to obtain the tin dioxide/copper/tin dioxide transparent conductive film.

Through detection, the transmittance of the tin dioxide/copper/tin dioxide transparent conductive film obtained in the embodiment is 90%, and the resistivity is as low as 2.18 × 10 ^-4 Ω·cm。

By adopting the process parameters of example 1, only the thickness of the copper layer is changed, and as can be seen from fig. 2, when the intermediate layer copper metal is not deposited, the film shows an amorphous state, and is not changed due to the change of the oxygen flow or the sputtering power during the sputtering deposition, and as the thickness of the intermediate layer copper film is increased, weak nanocrystals appear in the film, which is because the X-ray diffractometer can detect the intermediate layer copper metal of the film, and the crystal face index is (111).

Example 2

1) cleaning the substrate: sequentially putting the glass substrate into acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning, wherein the cleaning time is 20min each time, and the cleaning temperature is 50 ℃; taking out the substrate after ultrasonic cleaning, wiping the substrate clean by using a dust-free cloth, and finally putting the substrate into a sputtering cavity of a remote source plasma sputtering system for sputtering;

before reactive sputtering, the sputtering chamber of the far-source plasma sputtering system is vacuumized to 9 x 10 ^-6 mbar, introducing argon of 70sccm into the chamber, and starting a plasma source emission system after the pressure in the chamber is kept stable so as to generate plasma at the plasma source; starting a plasma bunching electromagnet to enable the plasma to bombard the target material and pre-sputter the target material;

in the reactive sputtering process, the power of a plasma emission source is 600W, the accelerating bias power of a target material is 100W, the sputtering speed is 4.5nm/min, the reactive sputtering time of the upper layer of tin dioxide and the lower layer of tin dioxide is 3min, the thickness of a copper film is 6nm, the sputtering temperature is 20 ℃, and the substrate temperature is normal temperature;

and after sputtering is finished, closing the baffle below the glass substrate, depositing a layer of nano film on the glass substrate to obtain a finished product, and naturally cooling to room temperature to obtain the tin dioxide/copper/tin dioxide transparent conductive film.

Through detection, the transmittance of the tin dioxide/copper/tin dioxide transparent conductive film obtained in the embodiment is 85%, and the resistivity is as low as 1.44 × 10 ^-4 Ω·cm。

It can be seen from fig. 3(a) that the film surface is very dense and uniform and no other impurities are found, which indirectly demonstrates the advantage of the remote plasma system in sputtering the film. Scanning spectra are respectively carried out at the magnification of 5000 times 8000 times 10000 times 50000 times and 100000 times, and as shown in a picture (b), a picture (c), a picture (d), a picture (e) and a picture (f), the surfaces of the thin films are quite smooth and uniform, no crystallization tendency exists on the surfaces, and the state of the tin dioxide thin film is verified to be amorphous, which corresponds to the XRD spectrum in figure 1.

Example 3

before reactive sputtering, the sputtering chamber of the far-source plasma sputtering system is vacuumized to 9 x 10 ^-6 mbar, introducing argon of 70sccm into the chamber, and starting a plasma source emission system after the pressure in the chamber is kept stable so as to generate plasma at the plasma source; starting the plasma bunching electromagnet to make the plasma bombard the target material to pre-sputter the target material；

in the reactive sputtering process, the power of a plasma emission source is 600W, the accelerating bias power of a target material is 100W, the sputtering speed is 4.5nm/min, the reactive sputtering time of the upper layer of tin dioxide and the lower layer of tin dioxide is 3min, the thickness of a copper film is 8nm, the sputtering temperature is 20 ℃, and the substrate temperature is normal temperature;

Through detection, the transmittance of the tin dioxide/copper/tin dioxide transparent conductive film obtained in the embodiment is more than 80%, and the resistivity is as low as 9.88 × 10 ^-5 Ω·cm。

It can be seen from fig. 4 that the thickness of the interlayer copper film has a significant effect on the transmittance of the film during the process of preparing the film by sputtering deposition. When no intermediate copper metal is deposited, the light transmittance of the film reaches 95%. As the thickness of the copper thin film increases, the light transmittance of the thin film also gradually decreases. When the thickness of the film is 4nm, the visible light transmittance reaches 90%, when the thickness of the film is 6nm, the visible light transmittance reaches 85%, and when the thickness of the film is 8nm, the visible light transmittance reaches 80%.

As shown in FIG. 5, it can be seen that as the thickness of the interlayer copper film increases, the film resistivity gradually decreases, since the film becomes more conductive and the film resistivity is substantially 10 ^-4 The quantity level of omega cm completely meets the requirement of the commercialized transparent conductive oxide film. For the Hall mobility and carrier concentration of the thin film, it can be seen from FIG. 5 that the Hall mobility of the thin film is 2-7cm ² Vs, carrier concentration up to 10 ²² cm ^-3 。

It can be seen from fig. 6 that all the films are in good ohmic contact with the electrodes. The contact does not create significant additional resistance and does not significantly alter the equilibrium carrier concentration within the semiconductor. The tin dioxide/copper/tin dioxide transparent conductive film and the metal form good ohmic contact, mainly because the carrier concentration in the film is very high and the conductivity of the film is very strong.

In order to prove that the upper and lower films are tin dioxide films, the tin dioxide film is annealed in fig. 7, and is subjected to an X-ray diffraction test, and the crystal structure of the film can be seen to be rutile phase tin dioxide.

Comparative example 1

The sputtering method of the tin dioxide film in example 2 was replaced by magnetron sputtering, and the other steps were the same as in example 2, and the transparent conductive film obtained had a light transmittance of 82% and a resistivity of 6.1 × 10 ^-4 Ω·cm。

Comparative example 2

The difference from example 2 is that: the thickness of the copper thin film was 12 nm. The transparent conductive film obtained had a light transmittance of 70% and a resistivity of 5.2X 10 ^-5 Ω·cm。

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A tin dioxide/copper/tin dioxide multilayer transparent conductive film is characterized in that: the tin dioxide film comprises a first tin dioxide film, a copper film and a second tin dioxide film which are sequentially overlapped, wherein the thickness of the copper film is less than 10nm and more than or equal to 1nm, the thickness of the tin dioxide film is 50-150nm, and the tin dioxide is an amorphous film;

the preparation method of the tin dioxide/copper/tin dioxide multilayer transparent conductive film comprises the following steps:

the method comprises the following steps of sputtering a first tin dioxide film, a copper film and a second tin dioxide film on a substrate in sequence by taking argon as a plasma gas source and oxygen as a reaction gas, wherein the tin dioxide film is deposited by reactive sputtering through a remote source plasma sputtering technology, and the copper film is deposited by sputtering through a direct current sputtering method;

the substrate is glass or a flexible substrate;

in the sputtering process, the temperature of the substrate is 20-30 ℃;

before use, the substrate is sequentially placed in acetone, isopropyl ketone, ethanol and deionized water for ultrasonic cleaning, the cleaning time is 15-25min each time, and the cleaning temperature is 45-55 ℃;

in the reactive sputtering process, the argon flow is 60-80sccm, and the pressure in the sputtering cavity is 3.7 multiplied by 10 ^-3 -4.0×10 ^- ³ mbar; after oxygen is introduced into the chamber, after the air pressure in the chamber and the voltage of the target material are stable, performing reactive sputtering to deposit a film;

the flow of oxygen is 1-10sccm when the tin dioxide film is prepared by reactive sputtering, the power of a plasma emission source is 500-1200W, the accelerating bias power of a target is 100-300W, and the sputtering time of the tin dioxide is 2-15 min;

the photoelectric property of the transparent conductive film is regulated and controlled by controlling the thickness of the copper film in the middle layer, the time for sputtering the copper film by direct current is 0-135s, 0s is not included, and the thickness of the copper film is less than 10nm and is more than or equal to 1 nm;

in the reactive sputtering process, the sputtering temperature is 20-50 ℃;

before the film is deposited by reactive sputtering, the method also comprises the step of pre-sputtering the target, and the bias voltage applied to the target is increased from low to high until the bias voltage power of the target is increased.

2. The tin dioxide/copper/tin dioxide multilayer transparent conductive film of claim 1, wherein: the thickness of the first tin dioxide film is 90-110nm, and the thickness of the second tin dioxide film is 90-110 nm.

3. The method for preparing the tin dioxide/copper/tin dioxide multilayer transparent conductive film as claimed in any one of claims 1 to 2, which is characterized in that: the method comprises the following steps:

4. The method for preparing the tin dioxide/copper/tin dioxide multilayer transparent conductive film according to claim 3, wherein the method comprises the following steps: the substrate is glass or a flexible substrate;

in the sputtering process, the temperature of the substrate is 20-30 ℃;

the substrate is sequentially placed in acetone, isopropyl ketone, ethanol and deionized water for ultrasonic cleaning before use, the cleaning time is 15-25min each time, and the cleaning temperature is 45-55 ℃.

5. The method for preparing the tin dioxide/copper/tin dioxide multilayer transparent conductive film according to claim 3, wherein the method comprises the following steps: in the reactive sputtering process, the argon flow is 60-80sccm, and the pressure in the sputtering cavity is 3.7 multiplied by 10 ^-3 -4.0×10 ^-3 mbar; after oxygen is introduced into the chamber, after the air pressure in the chamber and the voltage of the target material are stable, performing reactive sputtering to deposit a film;

the flow rate of oxygen is 1-10sccm when the tin dioxide film is prepared by reactive sputtering, the power of a plasma emission source is 500-1200W, the accelerating bias power of a target is 100-300W, and the sputtering time of the tin dioxide is 2-15 min;

the time for sputtering the copper film by direct current is 0-135s, which does not contain 0s, and the thickness of the copper film is less than 10nm and is more than or equal to 1 nm;

in the reactive sputtering process, the sputtering temperature is 20-50 ℃.

6. The method for preparing the tin dioxide/copper/tin dioxide multilayer transparent conductive film according to claim 3, wherein the method comprises the following steps: the purity of the tin target and the copper target is 4N-5N.

7. The method for preparing the tin dioxide/copper/tin dioxide multilayer transparent conductive film according to claim 3, wherein the method comprises the following steps: before the film is deposited by reactive sputtering, the method also comprises the step of pre-sputtering the target, and the bias voltage applied to the target is increased from low to high until the bias voltage power of the target is increased.

8. The method for preparing the tin dioxide/copper/tin dioxide multilayer transparent conductive film according to claim 3, wherein the method comprises the following steps: the initial bias applied to the target was 40-60W, with incremental values of 40-60W.

9. Use of the tin dioxide/copper/tin dioxide multilayer transparent conductive film according to any one of claims 1 to 2 in the field of flat panel displays, solar cells, microwave shielding and goggles, sensors.