JP2009018947A - Carbon nanotube thin film - Google Patents
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本発明は、カーボンナノチューブ薄膜、光透過率の変動が小さく、面抵抗の変動が小さく、安定した導電性を有するカーボンナノチューブ薄膜に関するものである。 The present invention relates to a carbon nanotube thin film, a carbon nanotube thin film having a small variation in light transmittance, a small variation in sheet resistance, and a stable conductivity.
カーボンナノチューブ（ＣＮＴ）は、１９９１年に非特許文献１に発表された。その後、ＣＮＴのもつ良好な特性が注目された。電界効果トランジスタや、ミクロサイズの配線材料などの次世代材料として用いられるものとしてＣＮＴに対する期待が大きい。現在使用されている、これらの材料として用いられている材料よりも優れた特性を有していることが期待される。その結果、これらの材料は、現在以上の特性が期待される潜在的な特性を有する材料として期待されるところとなり、積極的に開発が進められてきた。現在では、稀少資源であるインジウムの代替物質として、カーボンナノチューブによる透明導電膜（透明電極）の開発及びその応用に期待が持たれている。 Carbon nanotube (CNT) was published in Non-Patent Document 1 in 1991. Thereafter, the good characteristics of CNTs were noted. CNTs are highly expected as next-generation materials such as field effect transistors and micro-sized wiring materials. It is expected to have properties superior to those currently used as these materials. As a result, these materials have been expected as materials having potential characteristics that are expected to exceed the current characteristics, and have been actively developed. At present, there are expectations for the development and application of transparent conductive films (transparent electrodes) using carbon nanotubes as substitutes for indium, a rare resource.
ＣＮＴには、そのグラフェンシートの巻き方によって、金属及び半導体性ＣＮＴが存在する。通常のＣＮＴ材料は、金属性及び半導体性ＣＮＴの混合物となっている。
ＣＮＴは、層の枚数が１層の単層ＣＮＴ、２層の２層ＣＮＴ、３層の３層ＣＮＴ、層の数が多数ある多層ＣＮＴが知られている。
可視光を透過する透明電極としては、導電性は最外層のみの性質でほとんど決まるため、層の数が少なく光吸収の弱い単層ＣＮＴ又は２層ＣＮＴが当面の目標となっている。最も望ましい電極材料は単層ＣＮＴがよい。これらＣＮＴの合成法は、従来、化学気相成長法、アーク放電法、レーザー蒸発法等どのいずれの方法によっても作製されてきた。これらの合成法ではいずれの方法であってもよい。
In CNT, metal and semiconducting CNT exist depending on how the graphene sheet is wound. Ordinary CNT material is a mixture of metallic and semiconducting CNTs.
As the CNT, there are known single-layer CNT having one layer, two-layer CNT, two-layer CNT, three-layer CNT, and multilayer CNT having a large number of layers.
As a transparent electrode that transmits visible light, conductivity is almost determined by the properties of only the outermost layer, and therefore, single-walled CNTs or two-walled CNTs with a small number of layers and weak light absorption are the immediate targets. The most desirable electrode material is single-walled CNT. Conventionally, these CNT synthesis methods have been produced by any method such as chemical vapor deposition, arc discharge, and laser evaporation. Any of these synthesis methods may be used.
単層ＣＮＴは、その炭素原子の結合及び並び方の相違により、半導体性ＣＮＴと金属性ＣＮＴの２種類がある。合成方法において半導体性ＣＮＴと金属性ＣＮＴが等確率で生成されとすれば、生成比は２対１とされる。従来の既存の合成法によれば、これら半導体性ＣＮＴと金属性ＣＮＴの混合物として得られ、それらは束を構成しているとされる。
この半導体性ＣＮＴと金属性ＣＮＴの混合物からなる薄膜を形成してみると、その電気伝導性は半導体性ＣＮＴと金属性ＣＮＴの双方が寄与することとなり、混合物からなる導電性は、伝導担体（キャリア）を注入させることにより大きく変化させることができることが知られている。例えば、大気中の酸素や水による正孔注入では、伝導度が高くなることが知られている。また、硫酸に含浸させることによっても、正孔を注入することができるので伝導度が高くなる。この伝導度の上昇の原因は、酸素や水、硫酸による電荷移動（キャリア注入）の結果、半導体性ＣＮＴのフェルミレベルを変化させて、電荷は価電子帯に入り、その結果、伝導度に寄与するキャリア濃度が著しく増大できる結果によるものと考えられる。
ＣＮＴ薄膜を透明導電膜として使用してみると、その薄膜の導電性が環境の変化に応じて、刻々変化してしまうということは材料の特性が刻々変化することを意味し、材料を特定の目的に使用するということから考えると実用化するうえでは障害となる。前記のように変化する原因は、大気中等に存在する酸素や水、二酸化炭素、各種浮遊分子等がＣＮＴ表面へ吸着すると、電荷移動が起こり、その結果、薄膜の導電性を変化させることになり、これが薄膜の導電性が変化する原因であると考えられる。これを解決する上からは、
現状のデバイスを使用する環境から考えると、大気中に存在する酸素や水等の分子からデバイスを完全に隔離して、その結果、薄膜の導電性を特定の値に維持することは困難である。
その結果、デバイスが大気中の酸素や水等の分子を吸着しても導電性が変化しない、導電性が安定に保たれているＣＮＴ薄膜が求められている。
When a thin film composed of a mixture of semiconducting CNTs and metallic CNTs is formed, both the semiconducting CNTs and metallic CNTs contribute to the electrical conductivity. It is known that it can be changed greatly by injecting a carrier. For example, it is known that the conductivity increases when holes are injected by oxygen or water in the atmosphere. Also, impregnation with sulfuric acid can inject holes, so that the conductivity is increased. The cause of this increase in conductivity is that, as a result of charge transfer (carrier injection) due to oxygen, water, and sulfuric acid, the Fermi level of semiconducting CNTs is changed, and the charge enters the valence band, thereby contributing to conductivity. This is considered to be due to the result that the carrier concentration can be significantly increased.
When using a CNT thin film as a transparent conductive film, the fact that the conductivity of the thin film changes with the change of the environment means that the characteristics of the material change every moment. Considering that it is used for the purpose, it becomes an obstacle to practical use. The cause of the change as described above is that when oxygen, water, carbon dioxide, various floating molecules, etc. present in the atmosphere are adsorbed on the CNT surface, charge transfer occurs, resulting in a change in the conductivity of the thin film. This is considered to be the cause of the change in the conductivity of the thin film. From the top to solve this,
Considering the environment in which the current device is used, it is difficult to completely isolate the device from molecules such as oxygen and water present in the atmosphere, and as a result, maintain the conductivity of the thin film at a specific value. .
As a result, there is a need for a CNT thin film in which the conductivity does not change even when the device adsorbs molecules such as oxygen and water in the atmosphere, and the conductivity is stably maintained.
本発明の課題は、使用環境に存在する酸素や水、二酸化炭素、各種浮遊分子等が表面に吸着し、その結果電荷移動を生じても、その分光透過率及び導電性が変化しないＣＮＴ薄膜を提供することである。 An object of the present invention is to provide a CNT thin film in which oxygen, water, carbon dioxide, various floating molecules, etc. existing in the environment of use are adsorbed on the surface and, as a result, charge transfer occurs, the spectral transmittance and conductivity do not change. Is to provide.
本発明者は上記課題を解決すべく鋭意研究し、以下の点を見いだして本発明を完成させた。
（１）通常のＣＮＴ材料は、金属性ＣＮＴ及び半導体性ＣＮＴの混合物となっている。
（２）この内の半導体性ＣＮＴにはエネルギーギャップがあるため、そのままでは良好な導電性は得られない。その理由は、酸素や水、酸などの物質が表面に吸着すると、電荷移動を生じて、伝導度が高い状態を示すと考えられる。
（３）ＣＮＴを構成する金属性ＣＮＴにはエネルギーギャップが無く、さらにフェルミレベル近傍の状態密度がエネルギーに依存しない電子構造を取るとされる（強結合理論）。その結果、一定の伝導度を有している。
（４）伝導度を一定の範囲に保つ上からは、半導体性ＣＮＴを用いることなく、金属性ＣＮＴのみを用いて薄膜を作製すれば、得られる薄膜は他の分子や物質が金属性ＣＮＴ表面に吸着して電荷移動を生じても、ＣＮＴ薄膜の導電性には大きな変化が生じない。
（５）酸素や水、二酸化炭素、各種浮遊分子等が表面に吸着し、電荷移動を生じても、その分光透過率及び導電性が変化しないＣＮＴ薄膜を得ようとするのであれば、
金属性ＣＮＴのみを用いて薄膜を作製すれば、得られる薄膜は他の分子や物質が金属性ＣＮＴ表面に吸着して電荷移動を生じても、ＣＮＴ薄膜の導電性に大きな変化が生じないこのではなかいと考えた。
（６）そこで、金属性ＣＮＴ９５重量％以上好ましくは９９重量％以上を含有する溶液から溶媒を除去してＣＮＴ薄膜を形成すると、酸素や水、二酸化炭素、各種浮遊分子等の物質を表面に吸着させた場合であっても、その分光透過率の変化を初期値の５％以下、導電性の面抵抗の変化を初期値の３０％以下におさえることができることを見出した。この薄膜を得ることにより、発明が解決しようとする課題を解決することができた。
The inventor has intensively studied to solve the above problems, and has found the following points to complete the present invention.
(1) A normal CNT material is a mixture of metallic CNT and semiconducting CNT.
(2) Since the semiconductor CNT among these has an energy gap, good conductivity cannot be obtained as it is. The reason is considered to be that when a substance such as oxygen, water, or acid is adsorbed on the surface, charge transfer occurs and the conductivity is high.
(3) The metallic CNT constituting the CNT has no energy gap, and the state density in the vicinity of the Fermi level is assumed to take an electronic structure independent of energy (strong coupling theory). As a result, it has a certain conductivity.
(4) From the viewpoint of keeping the conductivity within a certain range, if a thin film is produced using only metallic CNT without using semiconducting CNT, the resulting thin film has other molecules and substances on the surface of metallic CNT. Even if it is adsorbed on the surface and causes charge transfer, there is no significant change in the conductivity of the CNT thin film.
(5) Even if oxygen, water, carbon dioxide, various floating molecules, etc. are adsorbed on the surface and charge transfer occurs, if you want to obtain a CNT thin film whose spectral transmittance and conductivity do not change,
If a thin film is produced using only metallic CNT, the resulting thin film will not cause a significant change in the conductivity of the CNT thin film even if other molecules and substances are adsorbed on the surface of the metallic CNT and cause charge transfer. I thought it was not good.
(6) Therefore, when the CNT thin film is formed by removing the solvent from the solution containing 95% by weight or more, preferably 99% by weight or more of the metallic CNTs, substances such as oxygen, water, carbon dioxide, and various floating molecules are adsorbed on the surface. It has been found that even if it is used, the change of the spectral transmittance can be suppressed to 5% or less of the initial value, and the change of the conductive surface resistance can be suppressed to 30% or less of the initial value. By obtaining this thin film, the problems to be solved by the invention could be solved.
本発明によれば、以下のことが可能となる。
（１）大気その他の環境中に含まれる分子がＣＮＴ表面に付着しても、その透明性及び導電性をほとんど変化させずに、安定した導電性を維持する導電性ＣＮＴ薄膜を得ることができる。基板上にＣＮＴ薄膜を形成し、デバイスとして使用できる。
（２）硫酸のような、酸化性の強い酸に７２時間含浸させても、酸に冒されて機能を失うことなく、導電特性をほとんど変えることなく、電極として機能するＣＮＴ薄膜を得ることができる。電極に使用することができる。
According to the present invention, the following becomes possible.
(1) Even when molecules contained in the atmosphere or other environment adhere to the CNT surface, a conductive CNT thin film that maintains stable conductivity can be obtained without changing the transparency and conductivity. . A CNT thin film can be formed on a substrate and used as a device.
(2) Even if impregnated with a highly oxidative acid such as sulfuric acid for 72 hours, it is possible to obtain a CNT thin film that functions as an electrode without being affected by the acid and losing its function, and hardly changing its conductive properties. it can. Can be used for electrodes.
本発明のＣＮＴ薄膜は、金属性ＣＮＴと半導体性ＣＮＴとから構成され、前記金属性ＣＮＴの割合は９５重量％以上１００％未満、好ましくは９９重量％以上１００％未満である。
ＣＮＴ薄膜は基板上に形成されていてもよいし、独立して膜状体を形成していてもよい。
薄膜の厚さは膜の形成方法により適宜調製することができる。
その透明性及び導電性をほとんど変化させずに、安定した導電性を維持する導電性ＣＮＴ薄膜を得ることができる。基板上にＣＮＴ薄膜を形成し、デバイスとして使用できる。
電極として機能するＣＮＴ薄膜を得ることができる。
金属性ＣＮＴは単層ＣＮＴにより構成される。
ＣＮＴの合成法は、公知の化学気相成長法、アーク放電法、レーザー蒸発法等どの方法によっても製造することができる。
The CNT thin film of the present invention is composed of metallic CNT and semiconducting CNT, and the ratio of the metallic CNT is 95% by weight or more and less than 100%, preferably 99% by weight or more and less than 100%.
The CNT thin film may be formed on a substrate, or may independently form a film-like body.
The thickness of the thin film can be appropriately adjusted depending on the method for forming the film.
A conductive CNT thin film that maintains stable conductivity can be obtained with little change in transparency and conductivity. A CNT thin film can be formed on a substrate and used as a device.
A CNT thin film that functions as an electrode can be obtained.
Metallic CNTs are composed of single-walled CNTs.
The CNT synthesis method can be produced by any known chemical vapor deposition method, arc discharge method, laser evaporation method or the like.
製造方法の一例を挙げると以下の通りである。
触媒の存在下にグラファイトにレーザー光を照射してＣＮＴを製造する方法。
平均粒径５ミクロンの高純度グラファイト粉末に、ニッケル酸化物およびコバルト酸化物の粉末をモル濃度比それぞれ０．６％、０．３％ずつ混合し、均一に混ぜ合わせたものを、フェノール樹脂でロッド状に整形固化させ、それを１２００℃で２時間、不活性ガス中で焼結したものをターゲットとした。このターゲットを窒素ガス７６０Torrの雰囲気を満たした石英管中に置き、窒素ガスを毎分１００cc程度流しながら、石英管全体を１０２５℃まで加熱した。ターゲット表面に４５０ｍJ/pulseのNd:YAGレーザー光を照射し、炭素およびニッケルおよびコバルトを蒸発させる。これらが電気炉内で凝集し形成された単層カーボンナノチューブが石英管内に付着したものを回収し、原料試料とする。原料試料を、過酸化水素濃度１５％の水に分散し、１００℃で１．５時間環流し、その後、塩酸で触媒金属を除去し、大気中で３５０℃まで加熱することにより残留塩酸を除去し、精製されたＣＮＴ（直径１．２±０．１ｎｍ）を得た。
An example of the manufacturing method is as follows.
A method of producing CNTs by irradiating graphite with laser light in the presence of a catalyst.
A high purity graphite powder with an average particle size of 5 microns is mixed with nickel oxide and cobalt oxide powders in a molar concentration ratio of 0.6% and 0.3% respectively, and uniformly mixed with a phenol resin. The target was shaped and solidified into a rod shape and sintered in an inert gas at 1200 ° C. for 2 hours. This target was placed in a quartz tube filled with an atmosphere of nitrogen gas 760 Torr, and the entire quartz tube was heated to 1025 ° C. while flowing about 100 cc of nitrogen gas per minute. The target surface is irradiated with 450 mJ / pulse Nd: YAG laser light to evaporate carbon, nickel and cobalt. The single-walled carbon nanotubes formed by agglomeration of these in an electric furnace are collected in the quartz tube and used as a raw material sample. The raw material sample is dispersed in water with a hydrogen peroxide concentration of 15% and refluxed at 100 ° C for 1.5 hours. Then, the catalyst metal is removed with hydrochloric acid, and the residual hydrochloric acid is removed by heating to 350 ° C in the atmosphere. As a result, purified CNT (diameter 1.2 ± 0.1 nm) was obtained.
金属性ＣＮＴの割合は９５重量％以上、好ましくは９９重量％以上である前記ＣＮＴは薄膜を得るためには、ＣＮＴを製造し、製造後の金属性ＣＮＴ及び半導体性ＣＮＴ混合物から前記割合の金属性ＣＮＴを得たのち、ＣＮＴ薄膜を製造することが行なわれる。このためには、ＣＮＴを製造して得られる金属性ＣＮＴと半導体ＣＮＴ組成物から金属性ＣＮＴを抽出分離して高濃度とすることが行なわれる。高濃度としては、９５重量％以上、好ましくは９９重量％以上とすることが行なわれる。 The proportion of metallic CNT is 95% by weight or more, preferably 99% by weight or more. In order to obtain a thin film, the CNT is produced by producing CNT, and the proportion of metal from the mixture of metallic CNT and semiconducting CNT after production. After obtaining the conductive CNT, a CNT thin film is produced. For this purpose, metallic CNT is extracted and separated from the metallic CNT obtained by producing CNT and the semiconductor CNT composition to obtain a high concentration. The high concentration is 95% by weight or more, preferably 99% by weight or more.
金属性ＣＮＴの抽出方法には、以下の方法が知られており、これらの各方法を適用することができる。
半導体性ＣＮＴと金属性ＣＮＴの混合物から金属性ＣＮＴを抽出する方法には、（１）アミンを分散剤として金属性ＣＮＴのみを可溶化して分離し、可溶化した溶液から金属性ＣＮＴを取り出す方法、（２）過酸化水素を用いて半導体性ＣＮＴを酸化させて酸化物として取り出し、金属性ＣＮＴを選択的に残し、金属性ＣＮＴを分離する方法、（３）ＤＮＡを用いて金属性ＣＮＴと半導体性ＣＮＴを分離する方法、（４）誘電泳動を用いて金属ＣＮＴを選択的に捕獲する方法、（５）界面活性剤とｉｏｄｉｘａｎｏｌ分子を用いて密度勾配遠心分離で金属性ＣＮＴと半導体性ＣＮＴを分離する方法がある。
これらの方法の中では、（１）アミンを分散剤として金属性ＣＮＴのみを可溶化する方法、又は（５）界面活性剤とｉｏｄｉｘａｎｏｌ分子を用いて密度勾配遠心分離で金属性ＣＮＴと半導体性ＣＮＴを分離する方法、さらに望ましくは、界面活性剤とｉｏｄｉｘａｎｏｌ分子を用いて密度勾配遠心分離で金属性ＣＮＴと半導体性ＣＮＴを分離する方法によることが有効である。
The following methods are known as extraction methods for metallic CNT, and these methods can be applied.
In the method of extracting metallic CNT from a mixture of semiconducting CNT and metallic CNT, (1) only metallic CNT is solubilized and separated using amine as a dispersant, and metallic CNT is taken out from the solubilized solution. Method, (2) Oxidizing semiconducting CNT using hydrogen peroxide and taking it out as oxide, leaving metallic CNT selectively and separating metallic CNT, (3) Metallic CNT using DNA (4) Method of selectively capturing metal CNTs using dielectrophoresis, (5) Metallic CNTs and semiconductors by density gradient centrifugation using surfactant and iodixanol molecules There is a method for separating CNTs.
Among these methods, (1) a method of solubilizing only metallic CNTs using an amine as a dispersant, or (5) metallic CNTs and semiconducting CNTs by density gradient centrifugation using a surfactant and iodixanol molecules. More preferably, it is effective to use a method in which metallic CNTs and semiconducting CNTs are separated by density gradient centrifugation using a surfactant and iodixanol molecules.
アミンを分散剤として金属性ＣＮＴのみを可溶化して分離し、可溶化した溶液から金属性ＣＮＴを取り出す方法は以下の通りである。
金属性ＣＮＴと半導体性ＣＮＴの混合物である合成後未処理のＣＮＴ粉末１ｍｇをプロピルアミンの５．０Ｍ テトラヒドロフラン溶液１０ｍｌに入れ、室温にて二時間超音波を照射した後、遠心分離機により、４５６２０ｇで１２時間、遠心分離を行う。その後、遠心管の上澄みを回収することにより、金属性ＣＮＴの割合が多いＣＮＴ分散液を得る。一回の処理では金属性ＣＮＴの純度は８７％程度であるので、この処理を複数回繰り返す事により、高純度の金属性ＣＮＴを得る。
A method of solubilizing and separating only metallic CNT using amine as a dispersant and taking out the metallic CNT from the solubilized solution is as follows.
After synthesis, 1 mg of untreated CNT powder, which is a mixture of metallic CNT and semiconducting CNT, is placed in 10 ml of a 5.0 M tetrahydrofuran solution of propylamine, irradiated with ultrasonic waves for 2 hours at room temperature, and then subjected to 45620 g using a centrifuge. Centrifuge for 12 hours. Thereafter, the supernatant of the centrifuge tube is collected to obtain a CNT dispersion having a high proportion of metallic CNTs. Since the purity of metallic CNT is about 87% in one treatment, high-purity metallic CNT is obtained by repeating this treatment a plurality of times.
（５）界面活性剤とｉｏｄｉｘａｎｏｌ分子を用いて密度勾配遠心分離で金属性ＣＮＴと半導体性ＣＮＴを分離する方法は以下の通りである。
（ア）ＣＮＴ孤立分散液の調整工程
原料ＣＮＴを含むコール酸ナトリウム水溶液に、超音波(ブランソンソニファイアー４５０Ｄ：レベル２)をかける。その後、その溶液に対して超遠心分離操作を行い、上部の液を取り出すことにより孤立ＣＮＴの分散水溶液を得る。
（イ）金属性ＣＮＴ分離用遠心管の調整工程
遠心管にコール酸ナトリウム（ＳＣ、シグマアルドリッチより購入：製品コード Ｃ６４４５）及びドデシル硫酸ナトリウム（ＳＤＳ、関東化学：コード３７２０３−１１、もしくはシグマアルドリッチより購入：製品コード Ｌ６０２６、）を混合させた溶液をｉｏｄｉｘａｎｏｌ分子含有水溶液（第一化学薬品より購入：製品名 Ｏｐｔｉｐｒｅｐ（ｉｏｄｉｘａｎｏｌ６０％水溶液））を用いて、濃度勾配（２０−４０％）をかけて配置する。この遠心管に、上記ＣＮＴ孤立分散水溶液にｉｏｄｉｘａｎｏｌ分子含有水溶液（第一化学薬品より購入：製品名 Ｏｐｔｉｐｒｅｐ（ｉｏｄｉｘａｎｏｌ６０％水溶液））を加えて濃度調整を行ったものを配置する。
（ウ）金属性ＣＮＴの分取工程
上記調製を行なった金属性ＣＮＴ分離用遠心管を遠心分離機（１９７０００Ｇ、２４時間の遠心分離。遠心分離機：日立工機製、ローター：Ｓ５２−ＳＴ）にかけ、遠心管内に金属性ＣＮＴが多く存在する部分と、半導体性ＣＮＴが多く存在する部分を形成することにより、金属性ＣＮＴ及び半導体性ＣＮＴの分離を行った。この遠心管内の液体を分取する事により、金属性ＣＮＴを多く含む金属性ＣＮＴ分散水溶液を得る。
（エ）金属性ＣＮＴの精製工程
金属性ＣＮＴを多く含む金属性ＣＮＴ分散水溶液に等量のメタノールを加え、孤立分散した金属性ＣＮＴを凝集させる。凝集させた金属性ＣＮＴを吸引濾過して取り出す。吸引ろ過して金属性ＣＮＴに含まれるｉｏｄｉｘａｎｏｌ分子、ドデシル硫酸ナトリウム、コール酸ナトリウムを除去する。
(5) A method for separating metallic CNT and semiconducting CNT by density gradient centrifugation using a surfactant and iodixanol molecules is as follows.
(A) Preparation process of CNT isolated dispersion An ultrasonic wave (Branson sonifier 450D: level 2) is applied to the sodium cholate aqueous solution containing the raw material CNT. Thereafter, an ultracentrifugation operation is performed on the solution, and the upper liquid is taken out to obtain a dispersed aqueous solution of isolated CNTs.
(I) Adjustment process of centrifuge tube for metallic CNT separation Sodium cholate (SC, purchased from Sigma Aldrich: product code C6445) and sodium dodecyl sulfate (SDS, Kanto Chemical: code 37203-11, or Sigma Aldrich) Purchase: A solution mixed with product code L6026) is placed with a concentration gradient (20-40%) using an iodixanol molecule-containing aqueous solution (purchased from Daiichi Kagaku: product name Optiprep (
(C) Metallic CNT fractionation step The centrifuge tube for metallic CNT separation prepared as described above is subjected to a centrifuge (197000G, centrifuge for 24 hours. Centrifuge: manufactured by Hitachi Koki, rotor: S52-ST). Then, the metallic CNT and the semiconducting CNT were separated by forming a portion in which the metallic CNT is present in the centrifuge tube and a portion in which the semiconducting CNT is present. By separating the liquid in the centrifuge tube, a metallic CNT-dispersed aqueous solution containing a large amount of metallic CNT is obtained.
(D) Metallic CNT purification step An equal amount of methanol is added to a metallic CNT-dispersed aqueous solution containing a large amount of metallic CNTs to aggregate isolated and dispersed metallic CNTs. Aggregated metallic CNTs are removed by suction filtration. Suction filtration is performed to remove iodixanol molecules, sodium dodecyl sulfate, and sodium cholate contained in the metallic CNT.
ＣＮＴ薄膜の形成は以下の通りである。
基板上もしくは自立性の薄膜を形成する方法には、以下の方法がある。
基板には石英、ポリマー、シリコン、化合物半導体を挙げることができる。
（ア）溶媒に分散した金属性ＣＮＴを、加熱した基板上にノズルから霧状に少しずつ吹き付けて成膜する。
（イ）溶媒に分散した金属性ＣＮＴを、ニトロセルロースを成分とするメンブレンフィルターを用いて濾過し、メンブレンフィルター上に金属性ＣＮＴ薄膜を形成する。メンブレンフィルターをアセトン等の溶媒に含浸させて溶解することにより除去し、残った金属性ＣＮＴ薄膜を基板上に付着させて溶媒を乾燥させて基板上に金属性薄膜を形成する。金属性ＣＮＴ薄膜は、真空中で２５０℃まで加熱後、１時間その温度を維持することにより、成膜過程で混入した溶媒や不純物を除去することができる。
（ウ）溶媒に分散した金属性ＣＮＴを、ニトロセルロースを成分とするメンブレンフィルターを用いて濾過し、メンブレンフィルター上に金属性ＣＮＴ薄膜を形成する。メンブレンフィルターをアセトン等の溶媒に含浸させて溶解することにより除去し、溶媒を乾燥させて自立した薄膜を形成する。金属性ＣＮＴ薄膜は、真空中で２５０℃まで加熱後、１時間その温度を維持することにより、成膜過程で混入した溶媒や不純物を除去することができる。
Formation of the CNT thin film is as follows.
There are the following methods for forming a self-supporting thin film on a substrate.
Examples of the substrate include quartz, polymer, silicon, and compound semiconductor.
(A) Metallic CNTs dispersed in a solvent are sprayed little by little from a nozzle onto a heated substrate to form a film.
(A) Metallic CNTs dispersed in a solvent are filtered using a membrane filter containing nitrocellulose as a component to form a metallic CNT thin film on the membrane filter. The membrane filter is removed by impregnating and dissolving in a solvent such as acetone, and the remaining metallic CNT thin film is adhered onto the substrate and the solvent is dried to form a metallic thin film on the substrate. The metallic CNT thin film can be heated to 250 ° C. in a vacuum and then maintained at that temperature for 1 hour to remove the solvent and impurities mixed in during the film formation process.
(C) Metallic CNTs dispersed in a solvent are filtered using a membrane filter containing nitrocellulose as a component to form a metallic CNT thin film on the membrane filter. The membrane filter is removed by impregnating with a solvent such as acetone and dissolved, and the solvent is dried to form a self-supporting thin film. The metallic CNT thin film can be heated to 250 ° C. in a vacuum and then maintained at that temperature for 1 hour to remove the solvent and impurities mixed in during the film formation process.
以下に本発明を実施例により説明する。
本発明は実施例により限定されるものではない。
Hereinafter, the present invention will be described by way of examples.
The present invention is not limited by the examples.
ＣＮＴの調製
平均粒径５ミクロンの高純度グラファイト粉末に、ニッケル酸化物およびコバルト酸化物の粉末をモル濃度比それぞれ０．６％、０．３％ずつ混合し、均一に混ぜ合わせたものを、フェノール樹脂でロッド状に整形固化させ、それを１２００℃で２時間、不活性ガス中で焼結したものをターゲットとした。このターゲットを窒素ガス７６０Torrの雰囲気を満たした石英管中に置き、窒素ガスを毎分１００cc程度流しながら、石英管全体を１０２５℃まで加熱した。ターゲット表面に４５０ｍJ/pulseのNd:YAGレーザー光を照射し、炭素およびニッケルおよびコバルトを蒸発させた。これらが電気炉内で凝集し形成された単層カーボンナノチューブが石英管内に付着したものを回収し、原料試料とした。原料試料を、過酸化水素濃度１５％の水に分散し、１００℃で１．５時間環流し、その後塩酸で触媒金属を除去し、大気中で３５０℃まで加熱する事により残留塩酸を除去し、精製されたＣＮＴ（直径１．２±０．１ｎｍ）を得た。
Preparation of CNT High purity graphite powder with an average particle size of 5 microns was mixed with nickel oxide and cobalt oxide powders in a molar concentration ratio of 0.6% and 0.3%, respectively, and uniformly mixed. The target was shaped and solidified into a rod shape with a phenol resin, and sintered in an inert gas at 1200 ° C. for 2 hours. This target was placed in a quartz tube filled with an atmosphere of nitrogen gas 760 Torr, and the entire quartz tube was heated to 1025 ° C. while flowing about 100 cc of nitrogen gas per minute. The target surface was irradiated with 450 mJ / pulse Nd: YAG laser light to evaporate carbon, nickel and cobalt. A single-walled carbon nanotube formed by aggregation in an electric furnace was collected in a quartz tube and used as a raw material sample. The raw material sample is dispersed in water with a hydrogen peroxide concentration of 15%, refluxed at 100 ° C for 1.5 hours, then the catalyst metal is removed with hydrochloric acid, and the residual hydrochloric acid is removed by heating to 350 ° C in the atmosphere. Purified CNT (diameter 1.2 ± 0.1 nm) was obtained.
ＣＮＴ孤立分散液の調整
３０ｍｇの上記原料ＣＮＴ（直径１．２±０．１ｎｍ）を含む３０ｍｌのコール酸ナトリウム２％水溶液に超音波(ブランソンソニファイアー４５０Ｄ：レベル２)を４時間かけた。その後、その溶液に対して１９７０００Ｇ１５分、超遠心分離操作を行い、上部９０％の液を取り出すことで孤立ＣＮＴ分散水溶液を得た。
Preparation of isolated CNT dispersion liquid Ultrasonic waves (Branson sonifier 450D: level 2) were applied to 30 ml of a 2% aqueous solution of sodium cholate containing 30 mg of the above raw material CNT (diameter 1.2 ± 0.1 nm) for 4 hours. Thereafter, the solution was subjected to an ultracentrifugation operation for 197000 G for 15 minutes, and the upper 90% liquid was taken out to obtain an isolated CNT-dispersed aqueous solution.
金属性ＣＮＴ分離用遠心管の調整
遠心管にコール酸ナトリウム（ＳＣ、シグマアルドリッチより購入：製品コード Ｃ６４４５）（０．６％）及びドデシル硫酸ナトリウム（ＳＤＳ、関東化学：コード３７２０３−１１、もしくはシグマアルドリッチより購入：製品コード Ｌ６０２６、）（２．４％）を混合させた溶液をｉｏｄｉｘａｎｏｌ分子含有水溶液（第一化学薬品より購入：製品名 Ｏｐｔｉｐｒｅｐ（ｉｏｄｉｘａｎｏｌ６０％水溶液））を用いて、濃度勾配（２０−４０％）をかけて配置した。この遠心管に、上記ＣＮＴ孤立分散水溶液にｉｏｄｉｘａｎｏｌ分子含有水溶液（第一化学薬品より購入：製品名 Ｏｐｔｉｐｒｅｐ（ｉｏｄｉｘａｎｏｌ６０％水溶液））を加えて濃度調整を行ったものを配置した。
Preparation of centrifuge tube for metallic CNT separation Sodium cholate (SC, purchased from Sigma-Aldrich: product code C6445) (0.6%) and sodium dodecyl sulfate (SDS, Kanto Chemical: code 37203-11, or Sigma) Purchased from Aldrich: Product code L6026,) (2.4%) mixed solution with iodixanol molecule-containing aqueous solution (purchased from Daiichi Kagaku: product name Optiprep (
金属性ＣＮＴの分取
上記遠心管を遠心分離機（１９７０００Ｇ、２４時間の遠心分離。遠心分離機：日立工機製、ローター：Ｓ５２−ＳＴ）にかけ、遠心管内に金属性ＣＮＴが多く存在する部分と、半導体性ＣＮＴが多く存在する部分を形成することにより、金属性ＣＮＴ及び半導体性ＣＮＴの分離を行った。この遠心管内の液体を分取する事により、金属性ＣＮＴを多く含む金属性ＣＮＴ分散水溶液（１）を得た。
Fractionation of metallic CNT The centrifuge tube is subjected to a centrifuge (197000G, centrifuge for 24 hours. Centrifuge: manufactured by Hitachi Koki Co., Ltd., rotor: S52-ST). The metallic CNT and the semiconducting CNT were separated by forming a portion where a large amount of semiconducting CNT was present. By separating the liquid in the centrifuge tube, a metallic CNT dispersion aqueous solution (1) containing a large amount of metallic CNTs was obtained.
金属性ＣＮＴ薄膜の作製
上記金属性ＣＮＴ分散水溶液（１）に等量のメタノール（和光純薬：特級）を加え、孤立分散した金属性ＣＮＴを凝集させた後、ポアサイズ１０ミクロンのフィルター（ミリポア オムニポアメンブレン）により吸引濾過し、金属性ＣＮＴ分散水溶液（１）に含まれるｉｏｄｉｘａｎｏｌ分子、ドデシル硫酸ナトリウム、コール酸ナトリウムを除去した。フィルター上に残された金属性ＣＮＴを再度メタノールに分散し、バス型超音波槽（シャープ製 ＵＴ−２０５Ｗ ２００Ｗ型超音波洗浄機）にて分散後、ポアサイズ１ミクロンのフィルター（ミリポア オムニポアメンブレン）により吸引濾過した。フィルター上に残された金属性ＣＮＴをＴｒｉｔｏｎ Ｘ−１００（関東化学より購入）０．５％水溶液に入れ、バス型超音波槽（シャープ製 ＵＴ−２０５Ｈ ２００Ｗ型超音波洗浄機）にて１時間分散し、金属性ＣＮＴ分散水溶液（２）を作製した。この金属性ＣＮＴ分散水溶液（２）をポアサイズ０．２２ミクロンのセルロース混合エステル製のメンブレンフィルター（ミリポア ＧＳＷＰ０２４００）にて吸引濾過し、フィルター表面に金属性ＣＮＴ薄膜を形成した。さらに純水（ミリポア ミリＱ Ｇｒａｄｉｅｎｔ）を薄膜上から注ぎながら吸引濾過を継続し、Ｔｒｉｔｏｎ Ｘ―１００を洗い流した後、室温にて乾燥させた。セルロース混合エステル製のメンブレンフィルターに付着した金属性ＣＮＴ薄膜をアセトン（和光純薬製：特級）中に石英板と共に入れ、セルロース混合エステル製のメンブレンフィルターをアセトンに溶解させて除去することにより、石英基板上に金属性ＣＮＴ薄膜を形成した。金属性ＣＮＴ薄膜を形成した石英基板をさらに新しいアセトンに２度含浸させ、セルロース混合エステル製のメンブレンフィルターの残存物を完全に溶解除去し、石英基板上に金属性ＣＮＴ薄膜を得た。金属性ＣＮＴ薄膜を１×１０―６Ｔｏｒｒに真空排気した石英管に入れ、２５０℃に加熱して１時間保持して乾燥し、金属性ＣＮＴ薄膜試料を得た。
Preparation of metallic CNT thin film After adding an equal amount of methanol (Wako Pure Chemicals: Special Grade) to the above metallic CNT dispersion aqueous solution (1) to agglomerate isolated and dispersed metallic CNTs, a filter with a pore size of 10 microns (Millipore Omni) By suction filtration through a pore membrane, iodixanol molecules, sodium dodecyl sulfate, and sodium cholate contained in the aqueous metallic CNT dispersion (1) were removed. Disperse the metallic CNT left on the filter in methanol again, disperse it in a bath-type ultrasonic bath (Sharp UT-205W 200W ultrasonic cleaner), and then filter with a pore size of 1 micron (Millipore Omnipore Membrane) And filtered with suction. The metallic CNT remaining on the filter is placed in a 0.5% aqueous solution of Triton X-100 (purchased from Kanto Chemical Co., Ltd.) for 1 hour in a bath-type ultrasonic bath (Sharp UT-205H 200W ultrasonic cleaner). Dispersion was performed to prepare a metallic CNT dispersion aqueous solution (2). This aqueous metallic CNT dispersion (2) was suction filtered with a cellulose mixed ester membrane filter (Millipore GSWP02400) having a pore size of 0.22 microns to form a metallic CNT thin film on the filter surface. Further, suction filtration was continued while pouring pure water (Millipore Milli Q Gradient) over the thin film, and Triton X-100 was washed away, followed by drying at room temperature. By putting the metallic CNT thin film attached to the cellulose mixed ester membrane filter into acetone (made by Wako Pure Chemicals: special grade) together with the quartz plate and dissolving the cellulose mixed ester membrane filter in acetone and removing it, A metallic CNT thin film was formed on the substrate. The quartz substrate on which the metallic CNT thin film was formed was further impregnated twice with fresh acetone, and the residue of the membrane filter made of cellulose mixed ester was completely dissolved and removed to obtain a metallic CNT thin film on the quartz substrate. The metallic CNT thin film was put into a quartz tube evacuated to 1 × 10 −6 Torr, heated to 250 ° C., held for 1 hour and dried to obtain a metallic CNT thin film sample.
比較例１
参照用ＣＮＴ薄膜の作製
本発明の金属性ＣＮＴ薄膜と通常の処理によるＣＮＴ薄膜と比較するため、参照用ＣＮＴ薄膜を作製した。
上記孤立ＣＮＴ分散水溶液に等量のメタノール（和光純薬：特級）を加え、孤立分散したＣＮＴを凝集させた後、ポアサイズ１０ミクロンのフィルター（ミリポア オムニポアメンブレン）により吸引濾過し、孤立ＣＮＴ分散水溶液に含まれるコール酸ナトリウムを除去した。フィルター上に残された参照用ＣＮＴを再度メタノールに分散し、バス型超音波槽（シャープ製 ＵＴ−２０５Ｈ ２００Ｗ型超音波洗浄機）にて分散後、ポアサイズ１ミクロンのフィルター（ミリポア オムニポアメンブレン）により吸引濾過した。フィルター上に残された参照用ＣＮＴをＴｒｉｔｏｎ Ｘ−１００（関東化学より購入）０．５％水溶液に入れ、バス型超音波槽（シャープ製 ＵＴ−２０５Ｈ ２００Ｗ型超音波洗浄機）にて１時間分散し、参照用ＣＮＴ分散水溶液を作製した。この参照用ＣＮＴ分散水溶液をポアサイズ０．２２ミクロンのセルロース混合エステル製のメンブレンフィルター（ミリポア ＧＳＷＰ０２４００）にて吸引濾過し、フィルター表面に参照用ＣＮＴ薄膜を形成した。さらに純水（ミリポア ミリＱ Ｇｒａｄｉｅｎｔ）を薄膜上から注ぎながら吸引濾過を継続し、Ｔｒｉｔｏｎ Ｘ―１００を洗い流した後、室温にて乾燥させた。セルロース混合エステル製のメンブレンフィルターに付着したＣＮＴ薄膜をアセトン（和光純薬製：特級）中に石英板と共に入れ、セルロース混合エステル製のメンブレンフィルターをアセトンに溶解させて除去することにより、石英基板上に参照用ＣＮＴ薄膜を形成した。参照用ＣＮＴ薄膜を形成した石英基板をさらに新しいアセトンに２度含浸させ、セルロース混合エステル製のメンブレンフィルターの残存物を完全に溶解除去し、石英基板上に参照用ＣＮＴ薄膜を得た。参照用ＣＮＴ薄膜を１×１０―６Ｔｏｒｒに真空排気した石英管に入れ、２５０℃に加熱して１時間保持して乾燥し、参照用ＣＮＴ薄膜試料を得た。
Comparative Example 1
Preparation of Reference CNT Thin Film A reference CNT thin film was prepared in order to compare the metallic CNT thin film of the present invention with a CNT thin film obtained by ordinary processing.
An equivalent amount of methanol (Wako Pure Chemicals: Special Grade) is added to the above isolated CNT-dispersed aqueous solution, and the isolated and dispersed CNTs are aggregated, and then suction filtered through a 10 micron pore size filter (Millipore Omnipore Membrane). The sodium cholate contained in was removed. The reference CNT left on the filter is dispersed again in methanol, dispersed in a bath-type ultrasonic bath (Sharp UT-205H 200W ultrasonic cleaner), and then a 1 micron pore size filter (Millipore Omnipore Membrane) And filtered with suction. The reference CNT left on the filter is placed in a 0.5% aqueous solution of Triton X-100 (purchased from Kanto Chemical) and 1 hour in a bath-type ultrasonic bath (Sharp UT-205H 200W ultrasonic cleaner). Dispersed to prepare a CNT-dispersed aqueous solution for reference. This reference CNT dispersion aqueous solution was subjected to suction filtration with a membrane filter made of cellulose mixed ester having a pore size of 0.22 microns (Millipore GSWP02400) to form a reference CNT thin film on the filter surface. Further, suction filtration was continued while pouring pure water (Millipore Milli Q Gradient) over the thin film, and Triton X-100 was washed away, followed by drying at room temperature. Place the CNT thin film adhering to the cellulose mixed ester membrane filter in acetone (Wako Pure Chemicals: Special Grade) together with the quartz plate, dissolve the cellulose mixed ester membrane filter in acetone and remove it. A CNT thin film for reference was formed. The quartz substrate on which the CNT thin film for reference was formed was further impregnated twice with new acetone, and the residue of the membrane filter made of cellulose mixed ester was completely dissolved and removed to obtain the CNT thin film for reference on the quartz substrate. The reference CNT thin film was placed in a quartz tube evacuated to 1 × 10 −6 Torr, heated to 250 ° C., held for 1 hour and dried to obtain a reference CNT thin film sample.
金属性ＣＮＴ薄膜中の金属性ＣＮＴ含有率の評価
上記金属ＣＮＴ薄膜と参照用ＣＮＴ薄膜の吸光度スペクトルを分光光度計（島津製作所：Ｓｏｌｉｄ Ｓｐｅｃ―３７００ＤＵＶ）にて測定した（図１）。
図1は金属性ＣＮＴ薄膜（実線）及び参照用ＣＮＴ薄膜（破線）の吸光度スペクトルを示している。
金属性ＣＮＴ薄膜における波長６００ｎｍの金属性ＣＮＴ固有の光吸収と波長１５００ｎｍの半導体性ＣＮＴ固有の光吸収の強度を参照用ＣＮＴにおける波長６００ｎｍの金属性ＣＮＴ固有の光吸収と波長１５００ｎｍの半導体性ＣＮＴ固有の光吸収の強度と比較することにより、金属性ＣＮＴ薄膜に含まれる金属性ＣＮＴの割合は約９９％、半導体性ＣＮＴの割合は約１％である事を得た。具体的には、２７０ｎｍの吸収は、炭素原子の総量によって決定される吸収であることから、２７０ｎｍの吸収ピーク強度で金属性ＣＮＴ薄膜の吸収スペクトルと参照用ＣＮＴ薄膜の吸収スペクトルを規格化した。この状態で、金属性ＣＮＴ由来の６００ｎｍの吸収強度を金属性ＣＮＴ薄膜と参照用ＣＮＴ薄膜の間で比較すると、参照用ＣＮＴ薄膜に含まれる金属性ＣＮＴの割合は約２０％で、残りの半導体性ＣＮＴの割合が約８０％であることがわかった。参照用ＣＮＴ薄膜の１５００ｎｍの半導体性ＣＮＴ由来の吸収強度と６００ｎｍの金属性ＣＮＴ由来の吸収強度の比と、金属性ＣＮＴ薄膜の１５００ｎｍの半導体性ＣＮＴ由来の吸収強度と６００ｎｍの金属性ＣＮＴ由来の吸収強度の比を比較すると、金属性ＣＮＴ薄膜では参照用ＣＮＴ薄膜の５００倍になっていることがわかった。参照用ＣＮＴ薄膜に含まれる金属性ＣＮＴの割合が２０％であることから、金属性ＣＮＴ薄膜に含まれる金属性ＣＮＴの割合は９９％であることが得られた。
Evaluation of metallic CNT content in metallic CNT thin film Absorbance spectra of the metallic CNT thin film and the reference CNT thin film were measured with a spectrophotometer (Shimadzu Corporation: Solid Spec-3700 DUV) (FIG. 1).
FIG. 1 shows absorbance spectra of a metallic CNT thin film (solid line) and a reference CNT thin film (broken line).
Intensity of light absorption unique to metallic CNT having a wavelength of 600 nm and light absorption inherent to semiconducting CNT having a wavelength of 1500 nm in the metallic CNT thin film The light absorption inherent to metallic CNT having a wavelength of 600 nm and semiconducting CNT having a wavelength of 1500 nm in the reference CNT By comparing with the inherent light absorption intensity, it was found that the proportion of metallic CNT contained in the metallic CNT thin film was about 99% and the proportion of semiconducting CNT was about 1%. Specifically, since the absorption at 270 nm is an absorption determined by the total amount of carbon atoms, the absorption spectrum of the metallic CNT thin film and the absorption spectrum of the reference CNT thin film were normalized with an absorption peak intensity of 270 nm. In this state, when the absorption intensity of 600 nm derived from metallic CNT is compared between the metallic CNT thin film and the reference CNT thin film, the ratio of metallic CNT contained in the reference CNT thin film is about 20%, and the remaining semiconductors It was found that the proportion of conductive CNT was about 80%. Ratio of absorption intensity derived from 1500 nm semiconducting CNT of the reference CNT thin film and absorption intensity derived from 600 nm metallic CNT, absorption intensity derived from 1500 nm semiconducting CNT of metallic CNT thin film, and 600 nm metallic CNT derived When the ratio of absorption intensity was compared, it was found that the metallic CNT thin film was 500 times that of the reference CNT thin film. Since the ratio of metallic CNT contained in the reference CNT thin film was 20%, it was obtained that the percentage of metallic CNT contained in the metallic CNT thin film was 99%.
可視光領域の光透過率（初期値）の測定
上記金属ＣＮＴ薄膜と参照用ＣＮＴ薄膜の分光透過率を分光光度計（島津製作所：Ｓｏｌｉｄ Ｓｐｅｃ―３７００ＤＵＶ）にて測定した（図２）。
左図は金属性ＣＮＴ薄膜の成膜直後（太実線）、硫酸含浸後（細実線）、成膜後１１日間大気暴露（太破線）の可視光領域の分光透過スペクトルである。
右図は参照ＣＮＴ薄膜の成膜直後（太実線）、硫酸含浸後（細実線）、成膜後１１日間大気暴露（太破線）の可視光領域の分光透過スペクトルである。
その結果、波長５００ｎｍにおける金属ＣＮＴ薄膜の透過率は５７％、参照用ＣＮＴ薄膜の透過率は３９％であった。
Measurement of Light Transmittance (Initial Value) in Visible Light Region The spectral transmittance of the metal CNT thin film and the reference CNT thin film was measured with a spectrophotometer (Shimadzu Corporation: Solid Spec-3700 DUV) (FIG. 2).
The left figure shows the spectral transmission spectrum in the visible light region immediately after deposition of the metallic CNT thin film (thick solid line), after impregnation with sulfuric acid (thin solid line), and after exposure to the atmosphere for 11 days (thick broken line).
The right figure shows the spectral transmission spectrum in the visible light region immediately after deposition of the reference CNT thin film (thick solid line), after impregnation with sulfuric acid (thin solid line), and after exposure to the atmosphere for 11 days (thick broken line).
As a result, the transmittance of the metal CNT thin film at a wavelength of 500 nm was 57%, and the transmittance of the reference CNT thin film was 39%.
面抵抗（初期値）の測定
上記金属ＣＮＴ薄膜と参照用ＣＮＴ薄膜の面抵抗を面抵抗計（ダイアインスツルメンツ ロレスタＥＰ）により４探針プローブ（ＰＳＰプローブ）で測定した。その結果、金属ＣＮＴ薄膜の面抵抗は０．９２ ｋΩ／□であった。一方、参照用ＣＮＴ薄膜の面抵抗は６．２ ｋΩ／□であった。
Measurement of surface resistance (initial value) The surface resistance of the metal CNT thin film and the reference CNT thin film was measured with a four-probe probe (PSP probe) using a surface resistance meter (Dia Instruments Loresta EP). As a result, the sheet resistance of the metal CNT thin film was 0.92 kΩ / □. On the other hand, the sheet resistance of the reference CNT thin film was 6.2 kΩ / □.
面抵抗の経時劣化の評価
ＣＮＴ薄膜の面抵抗の経時劣化（大気暴露）を調べるため、成膜後１１日間室温の大気に暴露したＣＮＴ薄膜の面抵抗の値を測定した。金属ＣＮＴ薄膜の作製後１１日後の面抵抗は０．８８ ｋΩ／□、参照用ＣＮＴ薄膜の作製後１１日後の面抵抗は７．１ ｋΩ／□であった。金属ＣＮＴ薄膜では約５％の面抵抗の減少、参照用ＣＮＴ薄膜では約１４％の面抵抗の上昇が観測され、金属ＣＮＴ薄膜の面抵抗変動は参照用ＣＮＴ薄膜の面抵抗変動よりも小さいことが示された。
Evaluation of surface resistance over time In order to investigate the surface resistance deterioration with time (exposure to the atmosphere) of the CNT thin film, the surface resistance value of the CNT thin film exposed to the air at room temperature for 11 days after film formation was measured. The sheet resistance 11 days after the production of the metal CNT thin film was 0.88 kΩ / □, and the sheet resistance 11 days after the preparation of the reference CNT thin film was 7.1 kΩ / □. A decrease in sheet resistance of about 5% was observed for the metal CNT thin film, and an increase in sheet resistance of about 14% was observed for the reference CNT thin film. The fluctuation of the sheet resistance of the metal CNT thin film was smaller than that of the reference CNT thin film. It has been shown.
分光透過率の経時劣化の評価
ＣＮＴ薄膜の分光透過率の経時劣化を調べるため、成膜から１１日後の分光透過率を測定した。図２参照。金属ＣＮＴ薄膜の作製後１１日後の波長５００ ｎｍにおける透過率は５７％、参照用ＣＮＴ薄膜の作製後１１日後の５００ ｎｍにおける透過率は３７％であった。金属ＣＮＴ薄膜の透過率の変動は０％、参照用ＣＮＴ薄膜の透過率の変動は５％であり、金属ＣＮＴ薄膜の透過率の経時変動が参照用ＣＮＴ薄膜よりも小さいことが示された。
Evaluation of temporal deterioration of spectral transmittance In order to examine the temporal deterioration of the spectral transmittance of the CNT thin film, the spectral transmittance 11 days after film formation was measured. See FIG. The transmittance at a wavelength of 500 nm 11 days after the production of the metal CNT thin film was 57%, and the transmittance at 500 nm 11 days after the production of the reference CNT thin film was 37%. The variation of the transmittance of the metal CNT thin film was 0%, the variation of the transmittance of the reference CNT thin film was 5%, and it was shown that the variation with time of the transmittance of the metal CNT thin film was smaller than that of the reference CNT thin film.
硫酸ドープによる面抵抗変動の評価
環境中の浮遊分子付着によるＣＮＴ薄膜の特性変動の加速実験のため、金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜に硫酸を含浸させ、面抵抗の変動を調べた。金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜表面に硫酸（和光純薬：特級純度９５％）を滴下し、そのまま密閉して３日間保った。その後、金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜表面の硫酸を純水にて洗い流し、余分な硫酸を除去後乾燥し、硫酸ドープ試料を得た。硫酸ドープした金属ＣＮＴ薄膜の面抵抗は、０．６５ ｋΩ／□であり、硫酸ドープした参照用ＣＮＴ薄膜の面抵抗は０．９９ ｋΩ／□であった。初期値と比較すると、金属ＣＮＴ薄膜では約３０％の面抵抗減少、参照用ＣＮＴ薄膜では、約８４％の面抵抗減少であった。硫酸ドープによる面抵抗の変化において、金属ＣＮＴ薄膜の方が参照用ＣＮＴ薄膜に比べて変動が小さいことが示された。
Evaluation of variation in surface resistance due to sulfuric acid doping In order to accelerate experiments on characteristics variation of CNT thin film due to adhesion of floating molecules in the environment, metal CNT thin film and reference CNT thin film were impregnated with sulfuric acid, and variation in surface resistance was investigated. Sulfuric acid (Wako Pure Chemicals: special grade purity 95%) was dropped onto the surfaces of the metal CNT thin film and the reference CNT thin film, sealed as it was, and kept for 3 days. Thereafter, sulfuric acid on the surfaces of the metal CNT thin film and the reference CNT thin film was washed away with pure water, and after removing excess sulfuric acid, drying was performed to obtain a sulfuric acid-doped sample. The sheet resistance of the metal CNT thin film doped with sulfuric acid was 0.65 kΩ / □, and the sheet resistance of the reference CNT thin film doped with sulfuric acid was 0.99 kΩ / □. Compared to the initial value, the sheet resistance was reduced by about 30% in the metal CNT thin film, and the sheet resistance was reduced by about 84% in the reference CNT thin film. In the change in surface resistance due to sulfuric acid doping, it was shown that the fluctuation of the metal CNT thin film was smaller than that of the reference CNT thin film.
硫酸ドープによる分光透過率変動の評価
環境中の浮遊分子付着によるＣＮＴ薄膜の特性変動の加速実験のため、金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜に硫酸を含浸させ、分光透過率の変動を調べた。金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜表面に硫酸（和光純薬：特級純度９５％）を滴下し、そのまま密閉して３日間保った。その後、金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜表面の硫酸を純水にて洗い流し、余分な硫酸を除去後乾燥し、硫酸ドープ試料を得た。硫酸ドープした金属ＣＮＴ薄膜の５００ ｎｍにおける透過率は５７％、硫酸ドープした参照用ＣＮＴ薄膜の５００ ｎｍにおける透過率は３５％であった。初期値と比較すると、金属ＣＮＴ薄膜の透過率の変動は約０％、参照用ＣＮＴ薄膜の透過率の変動は約１０％であった。金属ＣＮＴ薄膜において、可視光の範囲で最も変動の大きな波長（６１０ｎｍ）においても硫酸ドープによる透過率の初期値に対する変動は約５％であり、金属ＣＮＴ薄膜の方が参照用ＣＮＴ薄膜に比べて硫酸ドープによる分光透過率の変動が小さい事が示された。
Evaluation of spectral transmittance variation due to sulfuric acid doping In order to accelerate experiments on CNT thin film characteristics variation due to adhesion of floating molecules in the environment, metallic CNT thin film and reference CNT thin film were impregnated with sulfuric acid, and the variation of spectral transmittance was investigated. Sulfuric acid (Wako Pure Chemicals: special grade purity 95%) was dropped onto the surfaces of the metal CNT thin film and the reference CNT thin film, sealed as it was, and kept for 3 days. Thereafter, sulfuric acid on the surfaces of the metal CNT thin film and the reference CNT thin film was washed away with pure water, and after removing excess sulfuric acid, drying was performed to obtain a sulfuric acid-doped sample. The transmittance at 500 nm of the metal CNT thin film doped with sulfuric acid was 57%, and the transmittance at 500 nm of the reference CNT thin film doped with sulfuric acid was 35%. Compared to the initial value, the fluctuation of the transmittance of the metal CNT thin film was about 0%, and the fluctuation of the transmittance of the reference CNT thin film was about 10%. In the metal CNT thin film, even at the wavelength with the largest variation in the visible light range (610 nm), the transmittance due to the sulfuric acid doping is about 5% with respect to the initial value, and the metal CNT thin film is compared with the reference CNT thin film. It was shown that the variation in spectral transmittance due to sulfuric acid doping was small.
大気暴露による面抵抗の変動の評価
大気暴露の効果を評価するため、金属ＣＮＴ薄膜及び参照用ＣＮＴ薄膜作製後、１１日間大気に暴露した試料の面抵抗を真空中で測定し、真空排気する前の面抵抗値と比較する事により、表面に吸着した分子が面抵抗に与える影響を調べた。作製後１１日間大気中に暴露した金属ＣＮＴ薄膜の真空排気する前の面抵抗は０．８８ ｋΩ／□であった。ロータリーポンプで１０分間真空排気した後に、真空中で測定した金属ＣＮＴ薄膜の面抵抗は０．８８ ｋΩ／□であった。作製後１１日大気中に暴露した参照用ＣＮＴ薄膜の真空排気する前の面抵抗は７．１ ｋΩ／□であった。ロータリーポンプで１０分間真空排気した後に、真空中で測定した参照用ＣＮＴ薄膜の面抵抗は７．４ ｋΩ／□であった。１１日間大気に暴露した金属ＣＮＴ薄膜の真空排気による面抵抗変動は約０％、１１日間大気に暴露した参照用ＣＮＴ薄膜の真空排気による面抵抗変動は約４％であり、金属ＣＮＴ薄膜の面抵抗に与える大気暴露の効果は、参照用ＣＮＴ薄膜よりも小さいことが示された。
以上の結果、金属性ＣＮＴ薄膜は、参照用ＣＮＴ薄膜に比べて面抵抗の値が初期値において非常に小さいだけでなく、金属性ＣＮＴ薄膜は参照用ＣＮＴ薄膜に比べて面抵抗の経時変化、大気暴露による変化、硫酸ドープによる変化が小さい事が明らかである。
Evaluation of variation in surface resistance due to atmospheric exposure In order to evaluate the effect of atmospheric exposure, after the metal CNT thin film and the reference CNT thin film were prepared, the surface resistance of the sample exposed to the atmosphere for 11 days was measured in vacuum and before evacuation. The effect of molecules adsorbed on the surface on the surface resistance was investigated by comparing with the surface resistance value. The surface resistance before vacuum evacuation of the metal CNT thin film exposed to the atmosphere for 11 days after production was 0.88 kΩ / □. After vacuum evacuation with a rotary pump for 10 minutes, the sheet resistance of the metal CNT thin film measured in vacuum was 0.88 kΩ / □. The surface resistance before vacuum evacuation of the reference CNT thin film exposed to the atmosphere on the 11th day after the production was 7.1 kΩ / □. The surface resistance of the CNT thin film for reference was 7.4 kΩ / □ measured in vacuum after evacuating for 10 minutes with a rotary pump. The surface resistance fluctuation due to vacuum evacuation of the metal CNT thin film exposed to the atmosphere for 11 days is about 0%, and the surface resistance fluctuation due to vacuum evacuation of the reference CNT thin film exposed to the air for 11 days is about 4%. The effect of atmospheric exposure on resistance was shown to be less than that of the reference CNT thin film.
As a result, the metallic CNT thin film has not only a very small initial surface resistance value compared to the reference CNT thin film, but the metallic CNT thin film has a temporal change in surface resistance compared to the reference CNT thin film. It is clear that changes due to atmospheric exposure and changes due to sulfuric acid dope are small.
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