JP7360161B2 - Laminated body, method for manufacturing the laminated body, and device provided with the laminated body - Google Patents

Description

The present disclosure relates to a laminate including carbon nanotube layers.

In recent years, development of thin film transistors that utilize the semiconductor properties of carbon nanotubes has been progressing. For example, by modifying the surface of a thermally oxidized film of a silicon substrate with amino groups and adsorbing carbon nanotubes to the amino groups, a thin carbon nanotube layer that functions as a channel layer of a transistor is formed.

JP 2018-168018 Publication

When considering applications to wearable devices and the like, it is preferable to form a thin film transistor by fixing carbon nanotubes to the surface of a plastic substrate. However, when using a plastic substrate that cannot be oxidized, it is not possible to form a modifying group by reacting a silane coupling agent or the like with the oxide film.

The present disclosure has been made in view of these problems, and one exemplary objective thereof is to provide a laminate including a carbon nanotube layer.

A laminate according to an embodiment of the present disclosure includes a resin layer provided on a substrate and a carbon nanotube layer provided on the resin layer. The resin layer includes a polymer having adsorption groups that adsorb carbon nanotubes and crosslinking sites in side chains.

Another aspect of the present disclosure is a method for manufacturing a laminate. This method involves the steps of coating a substrate with a polymer that has an adsorption group that adsorbs carbon nanotubes and a crosslinking group in its side chain, and then reacting and bonding the adsorption group and crosslinking group of the polymer, or A step of forming a resin layer containing a polymer having a crosslinking site on the substrate by reacting and bonding the crosslinking group with another crosslinking group that the chain has, and a step of forming a carbon nanotube layer on the resin layer. Equipped with.

Yet another aspect of the disclosure is a device. This device includes a laminate of a certain embodiment and an electrode provided on the carbon nanotube layer of the laminate.

Note that any combination of the above components, and mutual substitution of the components and expressions of the present disclosure among methods, systems, etc., are also effective as aspects of the present disclosure.

According to the present disclosure, a laminate including carbon nanotube layers can be provided.

FIG. 1 is a cross-sectional view schematically showing the structure of a laminate according to an embodiment. It is a figure which shows typically the crosslinking reaction of the polymer of a resin layer. It is a flowchart which shows the flow of the manufacturing method of the layered product concerning an embodiment. This is an AFM image of a carbon nanotube layer. 2 is a graph showing the thickness distribution of a resin layer and a carbon nanotube layer. 1 is a cross-sectional view schematically showing the structure of a transistor according to an embodiment. 3 is a graph showing operating characteristics of a transistor.

First, an overview of the present disclosure will be explained. The present disclosure relates to a method of forming a thin film of carbon nanotubes (carbon nanotube layer) on a substrate. The present disclosure particularly aims at forming a semiconducting carbon nanotube layer that is applicable to a channel layer of a transistor. As a conventional problem, it is known that when carbon nanotubes constituting a channel layer aggregate into bundles and overlap in the thickness direction (bundling), the on-off ratio of a transistor decreases. Therefore, the carbon nanotube layer used as the channel layer is preferably configured so that a plurality of carbon nanotubes are not bundled, and preferably has a thickness as small as possible.

As a method for forming a thin carbon nanotube layer, a method has been proposed in which an adsorption group such as an amino group that adsorbs carbon nanotubes is formed on the substrate surface, and the carbon nanotubes are fixed to the substrate surface by the adsorption group. As a method for forming adsorption groups, there is a method of oxidizing the surface of a silicon substrate or the like and reacting a silane coupling agent or the like with the oxide film to form adsorption groups. However, this method cannot be applied to plastic substrates that cannot be subjected to oxidation treatment. When considering applications to wearable devices and the like, it is preferable to form a thin film transistor by fixing carbon nanotubes to the surface of a plastic substrate.

Therefore, the present disclosure proposes a method for fixing carbon nanotubes on a substrate surface without using oxidation treatment. Specifically, a resin layer containing a polymer having an adsorption group that adsorbs carbon nanotubes is formed on the substrate surface, and the carbon nanotubes are fixed using the adsorption groups of the resin layer. Furthermore, by crosslinking the polymers constituting the resin layer, deformation and peeling of the resin layer are prevented, and the carbon nanotube layer formed on the resin layer is stably fixed.

Hereinafter, embodiments for implementing the present disclosure will be described in detail with reference to the drawings. In addition, in the description, the same elements are given the same reference numerals, and redundant description will be omitted as appropriate.

FIG. 1 is a diagram schematically showing the structure of a laminate 10 according to an embodiment. The laminate 10 includes a substrate 12, a resin layer 14, and a carbon nanotube layer 16.

The substrate 12 is made of any inorganic or organic material. An example of the substrate 12 is a plastic substrate. The substrate 12 may be a rigid substrate that does not easily deform, or may be a flexible substrate that is flexible or stretchable.

The resin layer 14 is provided on the substrate 12. The resin layer 14 has a function of adsorbing carbon nanotubes constituting the carbon nanotube layer 16 and fixing the carbon nanotube layer 16 to the substrate 12. The resin layer 14 is made of a polymer having adsorption groups in side chains that have the property of adsorbing carbon nanotubes. An example of an adsorption group is a functional group containing a nitrogen atom, such as an amino group (-NH ₂ , -NHR or -NRR), a cyano group (-CN), an imino group (-C=NH or -C=NR ). Note that other functional groups capable of adsorbing carbon nanotubes may be used, or aromatic functional groups that interact with π electrons of carbon nanotubes may be used.

The polymers constituting the resin layer 14 are crosslinked with each other, and have covalent crosslinking sites, for example. By forming the resin layer 14 with a crosslinked polymer, the durability of the resin layer 14 can be increased and deformation and peeling of the resin layer 14 can be prevented. The polymer constituting the resin layer 14 has a crosslinking group in a side chain for crosslinking between polymers. The crosslinking group that the polymer has may be configured to crosslink by reacting with the adsorption group that the polymer has. The crosslinking group that the polymer has may be configured to react with a crosslinking agent and crosslink. Further, the polymer may have a first type of crosslinking group and a second type of crosslinking group, and may be configured such that the first type of crosslinking group and the second type of crosslinking group react and crosslink.

化学式（１）で表されるポリマーは、ポリアリルアミンの一部のアミノ基をメトキシカルカルボニル化することで得られ、吸着基としてアミノ基を有し、架橋基としてメトキシカルボニル基を有する。 As an example of the polymer constituting the resin layer 14, "partially methoxycarbonylated polyallylamine" represented by the following chemical formula (1) can be used.

The polymer represented by the chemical formula (1) is obtained by methoxycarbonylating some amino groups of polyallylamine, and has an amino group as an adsorption group and a methoxycarbonyl group as a crosslinking group.

FIG. 2 is a diagram schematically showing the crosslinking reaction of the polymer of the resin layer 14, and shows the crosslinking reaction between two polymers represented by the chemical formula (1). As shown in the figure, the amino group and the methoxycarbonyl group react, methanol is eliminated, and the polymers are crosslinked by the ureylene bond (-NHCONH-). Note that it is not necessary that all the adsorption groups and crosslinking groups of the polymer constituting the resin layer 14 react and crosslink, and only some of the adsorption groups and crosslinking groups may undergo the crosslinking reaction. As a result, adsorption groups (amino groups) remain in the resin layer 14 after the crosslinking reaction.

Returning to FIG. 1, the carbon nanotube layer 16 is provided on the resin layer 14. The carbon nanotube layer 16 is substantially composed only of carbon nanotubes, and is fixed on the resin layer 14 by adsorbing the carbon nanotubes to the adsorption groups of the resin layer 14 . The carbon nanotube layer 16 is configured to mainly contain, for example, semiconductor-type single-walled carbon nanotubes (SWCNT), and to have a low content of multi-walled carbon nanotubes and metallic single-walled carbon nanotubes. The content of semiconducting single-walled carbon nanotubes in the carbon nanotube layer 16 is, for example, 90% or more, preferably 95% or more or 99% or more. The thickness of the carbon nanotube layer 16 is 5 nm or less, preferably 2 nm or less or 1 nm or less. The carbon nanotubes contained in the carbon nanotube layer 16 are preferably not aggregated into bundles.

FIG. 3 is a flowchart showing the flow of the method for manufacturing the laminate 10 according to the embodiment. First, a polymer for forming the resin layer 14 is applied onto the substrate 12 (S12). For example, a non-crosslinked resin layer can be formed on the substrate 12 by dropping a solution containing a polymer onto the substrate 12 and performing spin coating. Next, the polymer is crosslinked to form the resin layer 14 (S12). For example, by heating the substrate 12, polymers forming the resin layer 14 can be crosslinked. Note that the polymers may be crosslinked by irradiation with ultraviolet light or the like.

Subsequently, a dispersion liquid in which carbon nanotubes are dispersed is applied onto the resin layer 14. At least a portion of the carbon nanotubes contained in the dispersion are adsorbed to the adsorption groups of the resin layer 14 and deposited on the resin layer 14 . The type of solvent used in the dispersion is not particularly limited, and may be water, for example. Therefore, an example of a dispersion liquid is an aqueous solution in which carbon nanotubes are dispersed. The dispersion liquid mainly contains, for example, semiconductor-type single-walled carbon nanotubes (SWCNT), and is configured such that the content of semiconductor-type single-walled carbon nanotubes is 90% or more, 95% or more, or 99% or more. In other words, the content of multi-walled carbon nanotubes and metallic single-walled carbon nanotubes is less than 10%, less than 5%, or less than 1%.

Subsequently, excess carbon nanotubes deposited on the resin layer 14 are removed using a fluid (S16). For example, excess carbon nanotubes not adsorbed on the resin layer 14 can be cleaned using a gas such as nitrogen gas or a liquid such as water or an organic solvent. Note that excess carbon nanotubes may be removed using a supercritical fluid such as carbon dioxide. Thereby, the carbon nanotubes that are adsorbed and fixed on the resin layer 14 can be selectively left, and the thickness of the carbon nanotube layer 16 formed on the resin layer 14 can be reduced. Through the above steps, the laminate 10 shown in FIG. 1 is completed.

FIG. 4 is an atomic force microscope (AFM) image of the carbon nanotube layer 16. The white, fibrous-looking parts in the image are carbon nanotubes. As shown in the figure, it can be seen that by fixing the carbon nanotubes using the resin layer 14, the carbon nanotube layer 16 can be formed over the entire in-plane area.

As a comparative example, when the resin layer 14 was not formed, the carbon nanotube layer 16 could not be fixed to the substrate 12. As another comparative example, when the polymer constituting the resin layer 14 was not crosslinked, the resin layer 14 deformed or peeled off, making it impossible to fix the carbon nanotube layer 16 to the substrate 12.

FIG. 5 is a graph showing the thickness distribution of the resin layer 14 and the carbon nanotube layer 16, and shows contour lines of the AFM image of FIG. As shown in the figure, the total thickness of the resin layer 14 and carbon nanotube layer 16 is within 14 nm, and although there are some peaks exceeding 10 nm, most of the thickness distribution is below 10 nm. I can see that The thickness of the carbon nanotube layer 16 is 5 nm or less, and most of the thickness of the carbon nanotube layer 16 is about 1 nm. Since the diameter of carbon nanotubes is about 1 nm, according to the present embodiment, it is possible to suppress the carbon nanotubes from forming bundles and overlapping in the thickness direction.

The stacked body 10 according to this embodiment can be applied to manufacturing thin film transistors.

FIG. 6 is a cross-sectional view schematically showing the structure of the transistor 40 according to the embodiment. The transistor 40 includes a substrate 42, a resin layer 44, a carbon nanotube layer 46, a gate electrode 48, a source electrode 50, and a drain electrode 52.

The substrate 42 is, for example, a plastic substrate. A resin layer 44 is formed on the substrate 42 . A carbon nanotube layer 46 is formed on the resin layer 44. The laminate of the substrate 42, the resin layer 44, and the carbon nanotube layer 46 corresponds to the laminate 10 described above. Gate electrode 48 is formed on the back surface of substrate 42. A source electrode 50 and a drain electrode 52 are formed on the carbon nanotube layer 46 with an interval corresponding to the channel length.

FIG. 7 is a graph showing the operating characteristics of the transistor 40, in which a crosslinked polymer represented by chemical formula (1) is used as the resin layer 44. As shown in the figure, the transistor 40 can realize an on-off ratio of about three digits, and it can be seen that it operates appropriately as a transistor. Therefore, the stacked body 10 according to this embodiment can be suitably applied to the thin film transistor 40.

The present disclosure has been described above based on the embodiments. Those skilled in the art will understand that the present disclosure is not limited to the embodiments described above, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present disclosure. It is a place where

In the embodiment described above, the case where the carbon nanotube layer 16 of the stacked body 10 is used as the semiconductor layer (channel layer) of the transistor 40 has been described. In a modification, the laminate 10 including the carbon nanotube layer 16 may be used for any purpose. For example, the carbon nanotube layer 16 may be used as a sensor. Further, the carbon nanotube layer 16 may be configured to substantially include only metallic carbon nanotubes, or may be configured to include a mixture of metallic and semiconductor carbon nanotubes.

In the above-described embodiment, the carbon nanotube layer 16 is formed by dropping a carbon nanotube dispersion onto the resin layer 14. In variations, other methods may be used to form the carbon nanotube layer 16. For example, the substrate 12 on which the resin layer 14 is formed may be immersed in a carbon nanotube dispersion liquid. The so-called LB (Langmuir-Blodgett) method may be used, in which a monomolecular film of carbon nanotubes is formed on the water surface, and the substrate 12 on which the resin layer 14 is formed is lifted from the water surface, so that the monomolecular film of carbon nanotubes is formed on the resin layer 14. A film may also be formed.

DESCRIPTION OF SYMBOLS 10... Laminate, 12... Substrate, 14... Resin layer, 16... Carbon nanotube layer, 40... Transistor, 42... Substrate, 44... Resin layer, 46... Carbon nanotube layer, 48... Gate electrode, 50... Source electrode, 52 ...Drain electrode.

Claims (8)

comprising a resin layer provided on a substrate and a carbon nanotube layer provided on the resin layer,
The resin layer includes a polymer having an adsorption group that adsorbs carbon nanotubes and a crosslinking site in a side chain,
The crosslinking site is formed by a reaction between a crosslinking group that the polymer has in a side chain and the adsorption group, or by a reaction between the crosslinking group and another crosslinking group that the polymer has in a side chain. A laminate characterized in that it is formed by bonding . The laminate according to claim 1 , wherein the adsorption group is an amino group, and the crosslinking group is a methoxycarbonyl group. The laminate according to claim 1 or 2 , wherein the thickness of the carbon nanotube layer is 5 nm or less. 4. The laminate according to claim 1, wherein the carbon nanotube layer includes semiconducting carbon nanotubes. a step of coating a substrate with a polymer having an adsorption group that adsorbs carbon nanotubes and a crosslinking group in its side chain;
The adsorption group of the polymer and the crosslinking group are reacted and bonded, or another crosslinking group that the polymer has in a side chain and the crosslinking group are reacted and bonded, thereby forming the polymer having a crosslinking site. forming a resin layer on the substrate,
A method for manufacturing a laminate, comprising the step of forming a carbon nanotube layer on the resin layer. 6. The method of manufacturing a laminate according to claim 5 , wherein the step of forming the carbon nanotube layer includes a step of applying a dispersion liquid in which carbon nanotubes are dispersed onto the resin layer. 7. The method for manufacturing a laminate according to claim 6 , wherein the step of forming the carbon nanotube layer further includes a step of removing carbon nanotubes that are not adsorbed to the resin layer. The laminate according to any one of claims 1 to 4 ,
A device comprising: an electrode provided on the carbon nanotube layer of the laminate.

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