CN110482530B

CN110482530B - Method for preparing patterned carbon nanotube film

Info

Publication number: CN110482530B
Application number: CN201910831550.0A
Authority: CN
Inventors: 韩杰; 王慧
Original assignee: Beijing Yuanxin Carbon Based Integrated Circuit Research Institute; Beijing Huatan Yuanxin Electronic Technology Co ltd
Current assignee: Beijing Yuanxin Carbon Based Integrated Circuit Research Institute; Beijing Huatan Yuanxin Electronic Technology Co ltd
Priority date: 2019-09-04
Filing date: 2019-09-04
Publication date: 2020-12-29
Anticipated expiration: 2039-09-04
Also published as: CN110482530A

Abstract

The invention discloses a method for preparing a patterned carbon nanotube film, which comprises the following steps: cleaning the substrate; carrying out hydrophobic modification on the cleaned substrate to enable the contact angle of the substrate to be larger than 90 degrees; and carrying out hydrophilic treatment on the hydrophobic modified substrate, wherein the hydrophilic treated area is matched with the area of the pattern. The method can rapidly realize the patterning of the substrate, and the formed pattern is clear and has simple process.

Description

Method for preparing patterned carbon nanotube film

Technical Field

The invention relates to the field of carbon nanotubes, in particular to a method for preparing a carbon nanotube film.

Background

Carbon nanotubes are a novel carbon material discovered by Iijima of NEC corporation of japan in 1991 and can be classified into single-walled carbon nanotubes and multi-walled carbon nanotubes. The special structure of the carbon nanotube determines the special properties of the carbon nanotube, such as high tensile strength and high thermal stability; the carbon nanotubes may exhibit metallic or semiconducting properties, etc., according to the change in the helical form of the carbon nanotubes. Because the carbon nano tube has an ideal one-dimensional structure and excellent properties in the fields of mechanics, electricity, thermal engineering and the like, the carbon nano tube has a wide application prospect in the fields of interdisciplines such as material science, chemistry, physics and the like, and is more and more concerned in scientific research and industrial application, but the carbon nano tube prepared under the general condition is granular or powdery, which causes great inconvenience to the application of people.

At present, Caoqing et al in the prior art use an LS method to prepare a carbon nanotube membrane, which is extruded back and forth at a certain speed by a push-pull plate; then, the carbon tube array on the solution is transferred to the substrate in parallel by the Langmuir-Schaefer method. Hongsik Park et al use trenching to allow carbon tubes to enter the trenches. Arnold et al, university of wisconsin, usa, uses the principle of evaporation to prepare a strip-shaped carbon tube.

However, the carbon nanotube film prepared by the method of Caoqing et al has the following disadvantages:

1. large area non-uniformities exist;

2. moreover, the carbon tube film is multi-layer, which has bad influence on the electrical performance (transistor), because the carbon tubes are stacked to form multi-layer in the process of repeated extrusion, and the process can not ensure that each site is really uniform.

The method of Hongsik Park or Arnold et al is used for preparing the carbon nano tube, and has the defects that the carbon nano tube obtained by the method is not a continuous film, but is in a strip shape, and is not suitable for the industrialized large-area processing technology; and the minimum size of the groove in the method of Arnold et al can only be made to 70nm, which has great limitation.

Besides, the drawbacks of the above method include: the solution can not be repeatedly used, which is relatively wasteful, and moreover, the film layer is not uniform and the quality is not high.

Disclosure of Invention

The invention aims to provide a preparation method for a patterned substrate and a preparation method for a carbon nanotube film, which have low cost, can form a patterned film and can effectively avoid the problem of uneven thickness of the carbon nanotube film.

According to one aspect of the invention, a method for preparing a carbon nanotube film on a patterned substrate mainly comprises the following steps:

a substrate patterning step: cleaning a substrate, carrying out hydrophobic modification on the substrate to enable a contact angle of the substrate to be larger than 90 degrees, and then forming a patterned hydrophilic region on the hydrophobic modified substrate;

self-assembly step: dripping a carbon nano tube solution into the liquid adding area on the substrate through a precise injection unit to ensure that the carbon nano tubes are fully paved in the strip of the hydrophilic area;

the substrate is subjected to drying and cleaning steps after the self-assembly is completed.

Preferably, the substrate is treated with ultraviolet ozone (UVO) for 10 minutes while cleaning the substrate.

Preferably, the hydrophobic modification is performed using an HMDS pretreatment system.

Preferably, the hydrophilic treatment comprises:

covering a metal mask plate on the substrate subjected to the hydrophobic modification, and treating the substrate covered with the mask plate by using an ultraviolet ozone cleaning machine (UVO).

Preferably, the hydrophilic treatment is photolithography.

Preferably, the carbon nanotube solution added dropwise in the self-assembly step is formed by dissolving carbon nanotubes in one or more halogenated hydrocarbons, and organic solvents such as chloroform, dichloroethane, trichloroethane, chlorobenzene, dichlorobenzene, bromobenzene and the like are preferred.

Preferably, a dispersing agent which interacts with the carbon nanotubes can be added into the carbon nanotube solution to form a carbon nanotube solution with the dispersing agent, and then the carbon nanotube solution with the dispersing agent is dispersed for 5min to 10min by adopting a water-area ultrasound or probe ultrasound or shaking table mode.

Preferably, the substance that forms an interaction with the carbon nanotube-dispersant complex is a polyol or a thiol, preferably 1% to 70% 3-methyl-propanediol.

Preferably, the injection slurry further comprises a tackifier, preferably polyethylene glycol or polystyrene.

Preferably, the drying temperature of the drying step is room temperature to 120 ℃, preferably 40 ℃ to 60 ℃, the pressure is 0.05MPa to 0.2MPa, and the drying time is 0.5h to 2 h. The drying method can be freeze drying or air drying.

Preferably, the cleaning temperature in the cleaning step is room temperature to 100 ℃, and the cleaning agent is one or more of isopropanol, toluene, xylene, N-methyl pyrrolidone or tetrahydrofuran.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing embodiments thereof with reference to the accompanying drawings in which:

FIG. 1 shows a flow chart of a process for preparing a patterned substrate of the present invention;

FIG. 2 shows a schematic diagram of the preparation of carbon nanotubes on a patterned substrate;

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in fig. 1, the present invention provides a method for preparing a carbon nanotube film on a patterned substrate, which mainly comprises the following steps:

(1) a substrate patterning step: firstly, cleaning a substrate, then carrying out hydrophobic modification on the substrate, forming a hydrophobic region 1 on the whole surface of the substrate, enabling the contact angle of the substrate to be larger than 90 degrees, and then forming a patterned hydrophilic region 2 on the hydrophobic modified substrate.

The substrate is selected from glass, metal or plastic, preferably glass. It may be flexible or rigid in shape, which is selected primarily based on the shape and properties of the film. The substrate is a base for forming the carbon nanotube thin film, and the shape thereof may be set according to a desired film shape, and may be a rectangle, a square, a circle, or other patterns or shapes, which is not limited herein.

The substrate is cleaned mainly to remove organic contaminants, a floating layer of silicon dioxide and the like on the surface of the substrate and improve the adhesion between the film layer and the substrate, and the cleaning method can be ultraviolet ozone cleaning machine (UVO) and high-temperature cleaning solvent, such as hydroxylamine (hydroxylamine) solvent, acetone and ethanol ultrasonic cleaning and the like.

Preferably, the cleaning method is ultraviolet ozone cleaning (UVO), which is a simple, economical and fast material surface cleaning device, and it is only necessary to place the sample on the sample plate, close the hatch, set the relevant parameters according to the actual workpiece condition, and operate.

At present, the ultraviolet ozone cleaning machine is mainly applied to surface UV light cleaning and surface UV light modification. The surface UV light cleaning utilizes ultraviolet light and OZONE generated therefrom to perform a photosensitive oxidative decomposition action on organic substances to remove organic compounds (hydrocarbons) adhered to the surface of an object, thereby obtaining an ultra-clean surface.

The surface UV light modification utilizes ultraviolet light to irradiate the organic surface, when the organic matter is decomposed, the ultraviolet light with the wavelength of 254nm is absorbed by the surface of the object, the chemical structure of the surface layer is cut, atomic oxygen generated by the action of photons is combined with the cut surface layer molecules and is converted into functional groups with high hydrophilicity (such as-OH, -CHO, -COOH), and thus, the wettability of the surface is improved.

And carrying out hydrophobic modification on the cleaned substrate, wherein the hydrophobic modification is realized by Hexamethyldisilazane (HMDS) treatment, alkyl hydrophobic group treatment, fluorocarbon hydrophobic group treatment and the like.

Preferably, the hydrophobic modification is HMDS, the chemical name of HMDS is hexamethyldisilazane, in the treatment process, HMDS is coated on the surface of a substrate, and a compound taking siloxane as a main body can be generated through heating and can react, so that the surface of the silicon wafer is successfully changed from hydrophilic to hydrophobic. The reaction principle of the HMDS and the silicon dioxide substrate is that moisture on the surface of the silicon dioxide substrate is removed through heating, then the HMDS and OH-on the surface of the silicon dioxide substrate react to form silicon ether on the surface of the silicon dioxide substrate, hydrogen bonds are eliminated, and the polar surface is changed into a non-polar surface.

Specifically, the work flow of HMDS processing is: and opening a vacuum pump for vacuum pumping, starting nitrogen filling after the vacuum degree in the cavity reaches a first high target value, performing vacuum pumping and nitrogen filling again until the vacuum degree reaches a first low target value, and keeping for a certain time after the target number of nitrogen filling is reached, so that the silicon dioxide substrate is fully heated, and the moisture on the surface of the silicon dioxide substrate is reduced. And then vacuumizing the HMDS pretreatment oven again to reach a certain vacuum degree, filling HMDS gas to reach a target value, fully reacting the HMDS gas with the silicon dioxide substrate, vacuumizing again after the reaction is finished, filling nitrogen and the like.

Through hydrophobic treatment, the contact angle of the silicon dioxide substrate is larger than 90 degrees, which is mainly because the contact angle is smaller than 90 degrees, the hydrophobicity is not enough, the limitation of the hydrophilic region cannot be obviously distinguished, and a clear pattern cannot be formed in the subsequent coating process.

Specifically, the substrate after the hydrophobic treatment is further subjected to hydrophilic treatment, wherein the hydrophilic treatment is performed only on the pattern portion, that is, only on the region to be patterned, instead of the entire substrate, and the other regions still remain hydrophobic, that is, the hydrophilic treatment region matches the pattern region.

The hydrophilic treatment mode comprises hydrophilic group modification, photoetching treatment, ultraviolet ozone cleaning machine (UVO) treatment or hydrophilic film attachment and the like. The method to be selected can be selected according to various aspects such as line width and equipment conditions. When the line width is more than 5 μm, ultraviolet ozone cleaning (UVO) treatment is preferable. The specific process is as follows: as mentioned above, the hydrophilic treatment is directed to the patterned region only, so that the other regions preferably cover a metal mask plate on the substrate after the hydrophobic modification, the shape of the mask plate being complementary to the shape of the pattern; that is, the mask covers the non-pattern area, and the pattern part is exposed. After the metal mask is covered, the substrate covered with the mask is treated by an ultraviolet ozone cleaning machine (UVO), for example, the substrate may be irradiated at 500W for 5 min. When the line width is less than 5 microns, preferably, the hydrophilic treatment is carried out by photoetching, firstly spin-coating a positive-throwing photoresist on the substrate subjected to hydrophobic modification by HMDS, then exposing and developing and fixing the line, then fixing the substrate subjected to oxygen plasma polishing, and finally cleaning the photoresist.

The method for preparing the patterned substrate is simple to operate, industrial popularization can be realized, and the formed substrate pattern is clear.

(2) Self-assembly step: and dripping a carbon nano tube solution into the liquid adding area on the substrate through a precise injection unit so that the carbon nano tubes are fully paved in the strip of the hydrophilic area.

When preparing the carbon nanotube solution, the carbon nanotube is dissolved in one or more kinds of halogenated hydrocarbons, and organic solvents such as chloroform, dichloroethane, trichloroethane, chlorobenzene, dichlorobenzene, bromobenzene, and the like are preferred. The carbon nanotubes are selected from single-wall carbon nanotubes, double-wall carbon nanotubes or multi-wall carbon nanotubes, and of course, two or more of the carbon nanotubes can be selected without affecting the quality of the film layer. Therefore, the method is convenient to select the carbon nano tube, does not need special treatment and is convenient for industrialized production. The halogenated hydrocarbon is preferably chloroform, dichloroethane, trichloroethane, chlorobenzene, dichlorobenzene or bromobenzene. The above halogenated hydrocarbon is used, and the carbon nanotube has better solubility.

And then adding a substance which forms interaction with the carbon nanotube-dispersant complex into the carbon nanotube solution, wherein the substance which forms interaction with the carbon nanotube-dispersant complex is polyalcohol or mercaptan, and the volume ratio of the additive to the carbon nanotube solution is 1-70%. If the proportion of the additive is less than 1 percent, the wetting effect is not obvious, and the phenomenon of delamination still occurs; the addition proportion is higher than 70%, the film forming quality is not high, the density of the carbon nano tube is low, and the carbon layer is too thin. In order to form a higher-quality film layer, the addition proportion is preferably 5-30%; more preferably 10%. This example uses 1% to 70% 3-methyl-propanediol. And then dispersing for 5min-10min by adopting a water area ultrasonic mode, a probe ultrasonic mode or a shaking table mode, wherein the dispersing time is not 5min in the embodiment, and forming the injection slurry of the carbon nano tube solution with the dispersing agent.

The injection slurry is injected into the substrate using a precision injection unit, which may be a printing probe or an injector, etc., that can precisely control the liquid volume. Specifically, the injection position of the precise injection unit on the substrate is a designed liquid adding area, and once the injection slurry is added, the injection slurry moves rapidly and is paved in a designed strip.

(3) And (3) drying: and further drying the formed patterned substrate, wherein the drying temperature is between room temperature and 120 ℃ in a vacuum environment when the film-forming substrate is dried, the drying temperature is preferably between 40 and 60 ℃, the pressure is between 0.05 and 0.2MPa, and the drying time is between 0.5 and 2 hours. The drying method can be freeze drying or air drying. In this example, the sample was dried for 1 hour by horizontally standing at 50 ℃ under a vacuum of 0.1 MPa.

(4) A cleaning step: and finally, cleaning the dried patterned substrate, wherein the cleaning agent selected in the cleaning process is one or more of isopropanol, toluene, xylene, N-methylpyrrolidone or tetrahydrofuran, the cleaning temperature is between room temperature and 100 ℃, preferably between 70 and 90 ℃, the cleaning time is between 10 and 60min, and the cleaning process is carried out by soaking at the temperature of 80 ℃ or shaking for 30 min.

In another embodiment of the present invention, the injection slurry may further include a tackifier, and the tackifier may be added to increase the viscosity of the carbon nanotube film and promote the uniformity of the film. Further, the tackifier can be polyethylene glycol or polystyrene, and the proportion of the tackifier is 10% -80%. The proportion of tackifier should not be too low, if it is less than 10%, this may result in evaporation of the liquid not spreading very slowly over the channel, and if it is too large, the carbon nanotube content may be reduced and the density may be problematic.

The substrate of the present invention has a pattern. The pattern of the substrate can be designed according to the requirement, so that a corresponding hydrophobic area and a hydrophilic area are formed, and the film layer matched with the pattern of the substrate is realized by utilizing the hydrophilic and hydrophobic properties. Through the patterning design of the substrate, more requirements can be met, and more abundant carbon nanotube film layers can be realized.

Although the invention has been described in detail hereinabove with respect to specific embodiments thereof, it will be apparent to those skilled in the art that modifications and improvements can be made thereto without departing from the scope of the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. A method for preparing a carbon nanotube film on a patterned substrate is characterized by mainly comprising the following steps:

a substrate patterning step: cleaning a substrate, performing hydrophobic modification on the substrate to enable a contact angle of the substrate to be larger than 90 degrees, and forming a patterned hydrophilic region on the hydrophobic modified substrate;

self-assembly step: dissolving carbon nanotubes in one or more halogenated hydrocarbons to form a carbon nanotube solution, adding a dispersant to form a carbon nanotube-dispersant complex, then adding 5-30% by volume of polyol or thiol interacting with the carbon nanotube-dispersant complex and 10-80% by volume of a tackifier, then further dispersing the carbon nanotube solution for 5-10 min by using water area ultrasound or probe ultrasound or a shaking table to form injection slurry, dropwise adding the injection slurry to a liquid adding area on the substrate through a precise injection unit to enable the injection slurry to be fully paved in a strip of a hydrophilic area, and then performing a drying step: the drying temperature is 40-60 ℃, the pressure is 0.05-0.2 MPa, and the drying time is 0.5-2 h;

and a cleaning step: the cleaning temperature is 70-90 ℃, and the cleaning agent is one or more of isopropanol, toluene, xylene, N-methyl pyrrolidone or tetrahydrofuran.

2. The method of claim 1, wherein the substrate is cleaned by treating the substrate with UV ozone for 10 minutes.

3. The method of claim 1, wherein the hydrophobic modification is performed by a hexamethyldisilazane pretreatment system.

4. The method of claim 1, wherein the substrate patterning step further comprises:

covering the substrate subjected to hydrophobic modification with a metal mask plate, and treating with an ultraviolet ozone cleaning machine.

5. The method of claim 1, wherein the substrate patterning step is performed by photolithography.

6. The method of claim 1, wherein the halogenated hydrocarbon is selected from chloroform, dichloroethane, trichloroethane, chlorobenzene, dichlorobenzene or bromobenzene.

7. The method of claim 1, wherein the adhesion promoter is polyethylene glycol or polystyrene.

8. The method for preparing carbon nanotube film on patterned substrate according to claim 1, wherein the drying manner in the drying step is freeze drying or air drying.