JP4863361B2 - Method for producing carbon nanotube - Google Patents

Method for producing carbon nanotube Download PDF

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JP4863361B2
JP4863361B2 JP2006088419A JP2006088419A JP4863361B2 JP 4863361 B2 JP4863361 B2 JP 4863361B2 JP 2006088419 A JP2006088419 A JP 2006088419A JP 2006088419 A JP2006088419 A JP 2006088419A JP 4863361 B2 JP4863361 B2 JP 4863361B2
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thin film
catalytic metal
carbon nanotube
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catalytic
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JP2007261867A (en
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英雄 長浜
和彦 松本
崇史 上村
雅俊 前田
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Panasonic Corp
Panasonic Electric Works Co Ltd
National Institute of Advanced Industrial Science and Technology AIST
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National Institute of Advanced Industrial Science and Technology AIST
Matsushita Electric Works Ltd
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本発明は、カーボンナノチューブの製造方法に関するものである。   The present invention relates to a method for producing carbon nanotubes.

近年、所謂ナノテクノロジーの分野において注目されているカーボンナノチューブを用いた種々のカーボンナノチューブ応用デバイス（例えば、電子放出素子、ディスプレイ、電界効果型トランジスタ、メモリ、半導体圧力センサ、半導体加速度センサなど）や、カーボンナノチューブの製造方法が各所で研究開発されている。   Various carbon nanotube application devices using carbon nanotubes that have been attracting attention in the field of so-called nanotechnology in recent years (for example, electron-emitting devices, displays, field-effect transistors, memories, semiconductor pressure sensors, semiconductor acceleration sensors, etc.) Carbon nanotube production methods are being researched and developed at various locations.

ここにおいて、カーボンナノチューブの製造方法の一例として、例えば、図３（ａ）に示すようにシリコン基板からなる基板１１の一表面上に導電性材料（例えば、Ｔｉ，Ｗなど）からなる導電層１２を例えば蒸着法やスパッタ法によって形成し、その後、図３（ｂ）に示すように導電層１２上にカーボンナノチューブの成長反応を促進するための触媒金属材料（例えば、Ｆｅ，Ｃｏ，Ｎｉ，Ｍｏなど）からなる触媒金属薄膜１３を例えば電子ビーム蒸着法によって形成し、その後、触媒金属薄膜１３をアルゴンガスなどの不活性ガス雰囲気中で加熱することで触媒金属薄膜１３を図３（ｃ）に示すように複数の微粒子状の触媒部１３ａに細分化し、続いて、原料ガスとして炭化水素系ガスを用いた熱ＣＶＤ法によって図３（ｄ）に示すようにカーボンナノチューブ１４を成長させるようにした製造方法が提案されている（例えば、特許文献１参照）。
ところで、上述のカーボンナノチューブの製造方法において導電層１２の代わりにＳｉＯ２膜のような絶縁層を形成するようにし、触媒部１３ａのみからカーボンナノチューブ１４を成長させるようにした製造方法も提案されている。
特開２００４−２６５３２号公報 Here, as an example of the carbon nanotube manufacturing method, for example, as shown in FIG. 3A, a conductive layer 12 made of a conductive material (for example, Ti, W, etc.) on one surface of a substrate 11 made of a silicon substrate. Is formed by, for example, vapor deposition or sputtering, and then a catalytic metal material (for example, Fe, Co, Ni, Mo for promoting the growth reaction of carbon nanotubes on the conductive layer 12 as shown in FIG. 3B). 3) is formed by, for example, an electron beam vapor deposition method, and then the catalytic metal thin film 13 is heated in an inert gas atmosphere such as argon gas to thereby form the catalytic metal thin film 13 in FIG. As shown in FIG. 3 (d), it is subdivided into a plurality of particulate catalyst parts 13a as shown in FIG. Manufacturing method so as to grow carbon nanotubes 14 have been proposed (e.g., see Patent Document 1).
By the way, a manufacturing method in which an insulating layer such as a SiO 2 film is formed in place of the conductive layer 12 in the above-described carbon nanotube manufacturing method and the carbon nanotubes 14 are grown only from the catalyst portion 13a has been proposed. Yes.
JP 2004-26532 A

ところで、上述のカーボンナノチューブの製造方法では、触媒金属薄膜１３を不活性ガス雰囲気中で加熱する際の加熱温度を最適化することにより各触媒部１３ａのサイズのばらつきを低減することができるが、微粒子状の触媒部１３ａの活性が低く、複数の触媒部１３ａのうちカーボンナノチューブ１４の成長基点となる触媒部１３ａの割合が数％〜１０％程度であり、触媒部１３ａの高活性化が望まれていた。   By the way, in the above-described carbon nanotube manufacturing method, it is possible to reduce the size variation of each catalyst portion 13a by optimizing the heating temperature when the catalytic metal thin film 13 is heated in an inert gas atmosphere. The activity of the catalyst part 13a in the form of fine particles is low, and the ratio of the catalyst part 13a serving as the growth base point of the carbon nanotube 14 among the plurality of catalyst parts 13a is about several percent to 10%. It was rare.

本発明は上記事由に鑑みて為されたものであり、その目的は、微粒子状の触媒部からより安定してカーボンナノチューブを成長させることが可能なカーボンナノチューブの製造方法を提供することにある。   The present invention has been made in view of the above reasons, and an object of the present invention is to provide a carbon nanotube production method capable of growing carbon nanotubes more stably from a particulate catalyst part.

請求項１の発明は、基板の一表面側に触媒金属材料からなる触媒金属薄膜を形成する薄膜形成工程と、前記触媒金属薄膜を酸素を含む雰囲気中で溶融させてから冷却することによって前記触媒金属薄膜を複数の粒子状の触媒部に細分化する細分化工程と、細分化工程にて形成された各触媒部を加熱して当該各触媒部をより小さなサイズの複数の微粒子状の触媒部に再細分化する再細分化工程と、再細分化工程の後で熱ＣＶＤ法によって微粒子状の触媒部からカーボンナノチューブを成長させるカーボンナノチューブ成長工程とを備えることを特徴とする。   According to the first aspect of the present invention, there is provided a thin film forming step of forming a catalytic metal thin film made of a catalytic metal material on one surface side of a substrate, and the catalyst metal thin film is melted in an atmosphere containing oxygen and then cooled. A subdivision process for subdividing a metal thin film into a plurality of particulate catalyst parts, and heating each catalyst part formed in the subdivision process to make each catalyst part a plurality of fine particle catalyst parts of smaller size And a carbon nanotube growth step in which carbon nanotubes are grown from a particulate catalyst portion by a thermal CVD method after the re-subdividing step.

この発明によれば、触媒金属薄膜を酸素を含む雰囲気中で溶融させてから冷却することによって前記触媒金属薄膜を複数の粒子状の触媒部に細分化し、細分化工程にて形成された各触媒部を加熱して当該各触媒部をより小さなサイズの複数の微粒子状の触媒部に再細分化した後、熱ＣＶＤ法によって触媒部からカーボンナノチューブを成長させることにより、カーボンナノチューブが成長する微粒子状の触媒部の割合が高くなり、微粒子状の触媒部からより安定してカーボンナノチューブを成長させることが可能になる。   According to this invention, the catalyst metal thin film is melted in an atmosphere containing oxygen and then cooled to subdivide the catalyst metal thin film into a plurality of particulate catalyst parts, and each catalyst formed in the subdivision process. After heating the part and re-subdividing each catalyst part into a plurality of finer catalyst parts of smaller size, the carbon nanotubes are grown from the catalyst part by thermal CVD method, so that the carbon nanotubes grow. The ratio of the catalyst part becomes high, and it becomes possible to grow carbon nanotubes more stably from the particulate catalyst part.

請求項２の発明は、請求項１の発明において、前記細分化工程では、前記触媒金属薄膜を溶融させる際の雰囲気を酸素ガス雰囲気とすることを特徴とする。   The invention of claim 2 is characterized in that, in the invention of claim 1, in the subdividing step, an atmosphere when the catalytic metal thin film is melted is an oxygen gas atmosphere.

この発明によれば、前記細分化工程において前記触媒金属薄膜を溶融させる際の雰囲気を大気とする場合に比べて、前記カーボンナノチューブ成長工程においてカーボンナノチューブが成長する前記触媒部の割合がより一層高くなるとともに、前記触媒部から成長するカーボンナノチューブの数が多くなる。   According to this invention, compared with the case where the atmosphere at the time of melting the catalytic metal thin film in the subdividing step is the atmosphere, the proportion of the catalyst part in which the carbon nanotubes grow in the carbon nanotube growing step is much higher. In addition, the number of carbon nanotubes growing from the catalyst portion increases.

請求項３の発明は、請求項１または請求項２の発明において、前記薄膜形成工程では、前記触媒金属薄膜の膜厚を量子サイズ効果により融点低下が起こる値に設定し、前記細分化工程では、前記触媒金属薄膜を溶融させる際に前記触媒金属材料の融点よりも低い温度で前記触媒金属薄膜を溶融させることを特徴とする。   According to a third aspect of the present invention, in the first or second aspect of the invention, in the thin film forming step, the thickness of the catalytic metal thin film is set to a value at which a melting point lowers due to a quantum size effect, and in the subdividing step, The catalyst metal thin film is melted at a temperature lower than the melting point of the catalyst metal material when the catalyst metal thin film is melted.

この発明によれば、前記触媒金属材料の融点よりも低い温度で前記触媒金属薄膜を溶融させることができるので、前記細分化工程のプロセス温度の低温化を図れる。   According to this invention, since the catalytic metal thin film can be melted at a temperature lower than the melting point of the catalytic metal material, the process temperature of the subdividing step can be lowered.

請求項４の発明は、請求項１ないし請求項３の発明において、前記カーボンナノチューブ成長工程では、前記カーボンナノチューブの成長温度を前記再細分化工程における加熱温度と同じ温度に設定することを特徴とする。   The invention of claim 4 is characterized in that, in the invention of claim 1 to claim 3, in the carbon nanotube growth step, the growth temperature of the carbon nanotube is set to the same temperature as the heating temperature in the re-segmentation step. To do.

この発明によれば、前記カーボンナノチューブ成長工程において前記再細分化工程にて形成された前記触媒部のサイズ、分散・配置状態などが変化するのを防止することができ、カーボンナノチューブが成長する前記触媒部の割合をより一層高めることができる。   According to this invention, in the carbon nanotube growth step, it is possible to prevent a change in the size, dispersion / arrangement state, etc. of the catalyst portion formed in the re-segmentation step, and the carbon nanotubes grow. The ratio of the catalyst part can be further increased.

請求項５の発明は、請求項１ないし請求項４の発明において、前記触媒金属材料として、Ｆｅ，Ｃｏ，Ｎｉ，Ｐｔ，Ｍｏの群から選択される１種類の材料を用いることを特徴とする。   A fifth aspect of the invention is characterized in that, in the first to fourth aspects of the invention, one material selected from the group of Fe, Co, Ni, Pt, and Mo is used as the catalytic metal material. .

この発明によれば、前記触媒金属薄膜を蒸着法やスパッタ法などの一般的な薄膜形成技術によって膜厚の制御性良く形成することができるので、前記細分化工程にて形成される粒子状の触媒部のサイズの制御が容易になる。   According to the present invention, since the catalytic metal thin film can be formed with a good film thickness controllability by a general thin film forming technique such as a vapor deposition method or a sputtering method, the particulate metal formed in the subdividing step can be formed. Control of the size of the catalyst part becomes easy.

請求項６の発明は、請求項１ないし請求項５の発明において、前記薄膜形成工程の前に前記基板の前記一表面側に前記カーボンナノチューブ成長工程における前記触媒部の触媒効果を抑制する触媒効果抑制層を形成する触媒効果抑制層形成工程を備え、前記薄膜形成工程では、前記触媒効果抑制層上に前記触媒金属薄膜を形成するようにし、前記触媒金属材料がＦｅであり、前記触媒効果抑制層が少なくとも前記触媒金属薄膜の下地となるＭｏ層からなることを特徴とする。 A sixth aspect of the present invention is the catalytic effect of the first to fifth aspects of the present invention, wherein the catalytic effect of suppressing the catalytic effect of the catalyst part in the carbon nanotube growth step on the one surface side of the substrate before the thin film forming step is achieved. comprising a catalytic effect inhibiting layer forming step of forming a suppression layer, in the thin film formation process, to so that to form the catalytic metal film on the catalytic effect suppression layer, the catalytic metal material is Fe, the catalyst effect The suppression layer is composed of at least a Mo layer serving as a base for the catalyst metal thin film .

この発明によれば、前記カーボンナノチューブ成長工程において前記各触媒部の触媒効果が抑制されるので、前記各触媒部それぞれから成長するカーボンナノチューブの数を低減することができ、複数のカーボンナノチューブが干渉して絡み合うのを防止することができる。   According to the present invention, since the catalytic effect of each catalyst part is suppressed in the carbon nanotube growth step, the number of carbon nanotubes growing from each catalyst part can be reduced, and a plurality of carbon nanotubes interfere with each other. And entanglement can be prevented.

ここで、この発明によれば、前記触媒金属材料としてＦｅを採用した場合に、前記カーボンナノチューブ成長工程における前記各触媒部の触媒効果をＭｏ層により抑制することができ、前記各触媒部それぞれから成長するカーボンナノチューブの数を低減することができる。 Here, according to this invention, the in the case of employing the Fe as the catalyst metallic material, wherein the carbon nanotube growth step the catalytic effect of the catalyst portion can be suppressed by Mo layer, wherein each catalyst portion, respectively Thus, the number of carbon nanotubes grown from can be reduced.

請求項１の発明では、微粒子状の触媒部からより安定してカーボンナノチューブを成長させることが可能になるという効果がある。   According to the first aspect of the invention, there is an effect that the carbon nanotubes can be more stably grown from the particulate catalyst portion.

以下、本実施形態のカーボンナノチューブの製造方法について図１を参照しながら説明する。   Hereinafter, the manufacturing method of the carbon nanotube of this embodiment is demonstrated, referring FIG.

まず、シリコン基板からなる基板１の一表面上にＳｉＯ２膜からなる絶縁層２を例えばＣＶＤ法や熱酸化法などにより形成する絶縁層形成工程を行うことによって、図１（ａ）に示す構造を得る。 First, the structure shown in FIG. 1A is formed by performing an insulating layer forming process in which an insulating layer 2 made of a SiO 2 film is formed on one surface of a substrate 1 made of a silicon substrate by, for example, a CVD method or a thermal oxidation method. Get.

絶縁層形成工程の後、絶縁層２上（つまり、基板１の上記一表面側）にカーボンナノチューブの成長反応を促進するための触媒金属材料（例えば、Ｆｅなど）からなる触媒金属薄膜３を例えば蒸着法やスパッタ法などにより形成する薄膜形成工程を行うことによって、図１（ｂ）に示す構造を得る。   After the insulating layer forming step, a catalytic metal thin film 3 made of a catalytic metal material (for example, Fe or the like) for promoting the growth reaction of carbon nanotubes on the insulating layer 2 (that is, the one surface side of the substrate 1) is, for example, The structure shown in FIG. 1B is obtained by performing a thin film forming process formed by vapor deposition or sputtering.

薄膜形成工程の後、触媒金属薄膜３を酸素を含む雰囲気中（本実施形態では、大気中）で加熱し溶融させてから冷却することによって触媒金属薄膜３を複数の粒子状の触媒部３ａに細分化する細分化工程を行うことによって、図１（ｃ）に示す構造を得る。ところで、上述の薄膜形成工程では、触媒金属薄膜３の膜厚を量子サイズ効果により融点低下が起こる値（例えば、数ｎｍ〜数１０ｎｍ）に設定してあり、細分化工程では、触媒金属薄膜３を溶融させる際に触媒金属材料の融点よりも低い温度で触媒金属薄膜３を溶融させるようにしているので、細分化工程のプロセス温度の低温化を図れる。なお、本実施形態では、細分化工程における触媒金属薄膜３の加熱温度を８００℃〜１０００℃の範囲、加熱時間を５分〜４０分の範囲で適宜設定している。   After the thin film formation step, the catalytic metal thin film 3 is heated in an atmosphere containing oxygen (in the present embodiment, in the air), melted, and then cooled to cool the catalytic metal thin film 3 into a plurality of particulate catalyst parts 3a. The structure shown in FIG. 1C is obtained by performing a subdividing step. By the way, in the above-mentioned thin film formation process, the film thickness of the catalytic metal thin film 3 is set to a value (for example, several nm to several tens of nm) at which the melting point is lowered due to the quantum size effect. Since the catalyst metal thin film 3 is melted at a temperature lower than the melting point of the catalyst metal material when melting the catalyst metal, the process temperature of the subdividing step can be lowered. In the present embodiment, the heating temperature of the catalytic metal thin film 3 in the subdividing step is appropriately set within a range of 800 ° C. to 1000 ° C. and the heating time is set within a range of 5 minutes to 40 minutes.

その後、上述の細分化工程にて形成された各触媒部３ａを加熱して当該各触媒部３ａをより小さなサイズ（ナノメータオーダのサイズ）の複数の微粒子状の触媒部３ｂに再細分化する再細分化工程を行うことによって、図１（ｄ）に示す構造を得る。ここで、再細分化工程は、酸素を含む雰囲気（本実施形態では、大気）で行うようにし、加熱温度を８００℃〜１０００℃の範囲、加熱時間を５分〜４０分の範囲で適宜設定している。なお、上述の細分化工程により形成される粒子状の触媒部３ａのサイズは例えば１０ｎｍ〜５００ｎｍの範囲でばらつき、再細分化工程により形成される微粒子状の触媒部３ｂのサイズは数ｎｍ〜数十ｎｍの範囲でばらついているが、再細分化工程を行うことにより、ナノ粒子化を促進することができるとともに、触媒部３ｂのばらつきを小さくすることができる。   Thereafter, each catalyst part 3a formed in the above-described subdividing step is heated to re-subdivide each catalyst part 3a into a plurality of finely divided catalyst parts 3b having a smaller size (nanometer order size). By performing the subdividing step, the structure shown in FIG. 1 (d) is obtained. Here, the re-segmentation step is performed in an atmosphere containing oxygen (in the present embodiment, air), and the heating temperature is appropriately set in the range of 800 ° C. to 1000 ° C. and the heating time in the range of 5 minutes to 40 minutes. is doing. In addition, the size of the particulate catalyst part 3a formed by the above-mentioned subdividing process varies, for example, in the range of 10 nm to 500 nm, and the size of the fine particle catalyst part 3b formed by the re-subdividing process is several nm to several Although it varies in the range of 10 nm, by performing the re-segmentation step, it is possible to promote the formation of nanoparticles and to reduce the variation of the catalyst part 3b.

そして、再細分化工程の後で熱ＣＶＤ法によって微粒子状の触媒部３ｂからカーボンナノチューブ４を成長させるカーボンナノチューブ成長工程を行うことによって、図１（ｅ）に示す構造を得る。ここにおいて、カーボンナノチューブ４の原料ガスとしては、炭化水素系ガス（例えば、Ｃ２Ｈ２ガス、Ｃ２Ｈ４ガス、ＣＨ４ガスなど）を用い、図１（ｅ）中の矢印で示すように基板１の上記一表面側の絶縁層２の表面に沿った一方向から原料ガスを供給する。なお、熱ＣＶＤ法によりカーボンナノチューブ４を成長させる際の基板温度（基板１の温度）は、原料ガスおよび触媒金属材料の種類に応じて例えば８００℃〜１０００℃の範囲で適宜設定すればよく、炭化水素系ガスの熱分解により励起状態になった反応種と触媒部３ｂとの触媒反応により、触媒部３ｂから炭素が析出する形でカーボンナノチューブ４が成長する。 And the structure shown in FIG.1 (e) is obtained by performing the carbon nanotube growth process which grows the carbon nanotube 4 from the particulate catalyst part 3b by a thermal CVD method after a re-segmentation process. Here, a hydrocarbon gas (for example, C 2 H 2 gas, C 2 H 4 gas, CH 4 gas, etc.) is used as a raw material gas for the carbon nanotubes 4, as indicated by an arrow in FIG. A source gas is supplied from one direction along the surface of the insulating layer 2 on the one surface side of the substrate 1. In addition, what is necessary is just to set suitably the substrate temperature at the time of growing the carbon nanotube 4 by thermal CVD method (temperature of the board | substrate 1), for example in the range of 800 to 1000 degreeC according to the kind of source gas and a catalyst metal material, The carbon nanotube 4 grows in a form in which carbon is deposited from the catalyst portion 3b by the catalytic reaction between the reactive species brought into an excited state by thermal decomposition of the hydrocarbon gas and the catalyst portion 3b.

以上説明したカーボンナノチューブの製造方法によれば、触媒金属薄膜３を酸素を含む雰囲気中で溶融させてから冷却することによって触媒金属薄膜３を複数の粒子状の触媒部３ａに細分化し、細分化工程にて形成された各触媒部３ａを加熱して当該各触媒部３ａをよりサイズの小さな複数の微粒子状の触媒部３ｂに再細分化した後、熱ＣＶＤ法によって触媒部３ｂからカーボンナノチューブ４を成長させることにより、カーボンナノチューブ４が成長する微粒子状の触媒部３ｂの割合が高くなり、微粒子状の触媒部３ｂからより安定してカーボンナノチューブ４を成長させることが可能になる。   According to the carbon nanotube manufacturing method described above, the catalytic metal thin film 3 is melted in an oxygen-containing atmosphere and then cooled, so that the catalytic metal thin film 3 is subdivided into a plurality of particulate catalyst parts 3a. Each catalyst part 3a formed in the process is heated to re-divide each catalyst part 3a into a plurality of finer catalyst parts 3b having smaller sizes, and then the carbon nanotubes 4 are formed from the catalyst part 3b by a thermal CVD method. As a result of the growth, the proportion of the particulate catalyst portion 3b on which the carbon nanotube 4 grows increases, and the carbon nanotube 4 can be grown more stably from the particulate catalyst portion 3b.

ところで、上述の製造方法では、細分化工程において触媒金属薄膜３を溶融させる際の雰囲気を大気としているが、酸素ガス雰囲気にすれば、触媒金属薄膜３を溶融させる際の雰囲気を大気とする場合に比べて、カーボンナノチューブ成長工程においてカーボンナノチューブ４が成長する触媒部３ｂの割合がより一層高くなるとともに、触媒部３ｂから成長するカーボンナノチューブ４の数が多くなる（カーボンナノチューブ４の成長密度が高くなる）。   By the way, in the above-mentioned manufacturing method, the atmosphere at the time of melting the catalytic metal thin film 3 in the subdividing step is the air. However, when the oxygen gas atmosphere is used, the atmosphere at the time of melting the catalytic metal thin film 3 is the air. In comparison with the above, in the carbon nanotube growth step, the proportion of the catalyst part 3b on which the carbon nanotubes 4 grow is further increased, and the number of carbon nanotubes 4 grown from the catalyst part 3b is increased (the growth density of the carbon nanotubes 4 is high). Become).

また、カーボンナノチューブ成長工程において、カーボンナノチューブ４の成長温度（上述の基板温度）を再細分化工程における加熱温度と同じ温度に設定すれば、カーボンナノチューブ成長工程において再細分化工程にて形成された触媒部３ｂのサイズ、分散・配置状態などが変化する（つまり、触媒部３ｂのマイグレーションが起こって凝集する）のを防止することができ、カーボンナノチューブ４が成長する触媒部３ｂの割合をより一層高めることができる。   Further, in the carbon nanotube growth process, if the growth temperature of the carbon nanotube 4 (the above-mentioned substrate temperature) is set to the same temperature as the heating temperature in the re-segmentation process, the carbon nanotube growth process is formed in the re-segmentation process. The size, dispersion / arrangement state, etc. of the catalyst part 3b can be prevented from changing (that is, the catalyst part 3b migrates and aggregates), and the proportion of the catalyst part 3b on which the carbon nanotubes 4 grow is further increased. Can be increased.

また、上述の実施形態では、触媒金属材料としてＦｅを採用した場合について例示したが、触媒金属材料は、Ｆｅに限らず、例えば、Ｃｏ，Ｎｉ，Ｍｏ,Ｐｔなどを採用してもよく、触媒金属材料として、Ｆｅ，Ｃｏ，Ｎｉ，Ｐｔ，Ｍｏの群から選択される１種類の材料を用いるようにすれば、触媒金属薄膜３を蒸着法やスパッタ法などの一般的な薄膜形成技術によって膜厚の制御性良く形成することができるので、細分化工程にて形成される粒子状の触媒部３ａのサイズの制御が容易になり、ひいては再細分化工程にて形成される微粒子状の触媒部３ｂのサイズの制御が容易になる。   Further, in the above-described embodiment, the case where Fe is employed as the catalytic metal material has been exemplified. However, the catalytic metal material is not limited to Fe, and for example, Co, Ni, Mo, Pt, etc. may be employed. If one kind of material selected from the group of Fe, Co, Ni, Pt, and Mo is used as the metal material, the catalytic metal thin film 3 is formed into a film by a general thin film forming technique such as a vapor deposition method or a sputtering method. Since the thickness can be formed with good controllability, the size of the particulate catalyst portion 3a formed in the subdividing step can be easily controlled, and as a result, the fine particulate catalyst portion formed in the re-subdividing step. Control of the size of 3b becomes easy.

ところで、上述の実施形態では、各触媒部３ｂから複数のカーボンナノチューブ４が成長し、特に細分化工程における雰囲気を酸素ガスとした場合には、各触媒部３ｂからより多くのカーボンナノチューブ４が成長するので、同じ触媒部３ｂから成長したカーボンナノチューブ４同士が絡み合ってしまうことがある。   By the way, in the above-described embodiment, a plurality of carbon nanotubes 4 grow from each catalyst part 3b, and more carbon nanotubes 4 grow from each catalyst part 3b, particularly when the atmosphere in the subdivision process is oxygen gas. Therefore, the carbon nanotubes 4 grown from the same catalyst part 3b may be entangled with each other.

そこで、薄膜形成工程の前に、図２に示すように基板１の上記一表面側にカーボンナノチューブ成長工程における触媒部３ｂの触媒効果を抑制する触媒効果抑制層５を形成する触媒効果抑制層形成工程を行い、上述の薄膜形成工程において触媒効果抑制層５上に触媒金属薄膜３を形成するようにすれば、カーボンナノチューブ成長工程において各触媒部３ｂの触媒効果が抑制されるので、各触媒部３ｂそれぞれから成長するカーボンナノチューブ４の数を低減することができ、複数のカーボンナノチューブ４が干渉して絡み合うのを防止することができる。   Therefore, before the thin film forming step, the catalytic effect suppressing layer formation is performed in which the catalytic effect suppressing layer 5 for suppressing the catalytic effect of the catalyst portion 3b in the carbon nanotube growth step is formed on the one surface side of the substrate 1 as shown in FIG. If the catalytic metal thin film 3 is formed on the catalytic effect suppressing layer 5 in the above-described thin film forming step, the catalytic effect of each catalyst portion 3b is suppressed in the carbon nanotube growth step. It is possible to reduce the number of carbon nanotubes 4 growing from each of 3b, and to prevent the plurality of carbon nanotubes 4 from interfering with each other.

ここにおいて、上述の触媒金属材料がＦｅの場合には、触媒効果抑制層５が少なくとも触媒金属薄膜３の下地となるＭｏ層を有していればよく、例えば、触媒効果抑制層５を、単層のＭｏ層、あるいは、下層のＳｉ層と上層のＭｏ層との積層膜により構成すれば、カーボンナノチューブ成長工程における各触媒部３ｂの触媒効果をＭｏ層により抑制することができ、各触媒部３ｂそれぞれから成長するカーボンナノチューブ４の数を低減することができる。要するに、各触媒部３ｂから成長するカーボンナノチューブの数を少量に抑制して各触媒部３ｂにおけるカーボンナノチューブ４の成長密度を小さくすることができる。   Here, when the above-described catalytic metal material is Fe, the catalytic effect suppressing layer 5 only needs to have at least a Mo layer serving as a base of the catalytic metal thin film 3. If the layer is composed of a Mo layer, or a laminated film of a lower Si layer and an upper Mo layer, the catalytic effect of each catalyst part 3b in the carbon nanotube growth step can be suppressed by the Mo layer. It is possible to reduce the number of carbon nanotubes 4 grown from each of 3b. In short, the growth density of the carbon nanotubes 4 in each catalyst part 3b can be reduced by suppressing the number of carbon nanotubes growing from each catalyst part 3b to a small amount.

なお、上述の実施形態では、基板１としてシリコン基板を用いているが、基板１はカーボンナノチューブ応用デバイスの仕様に応じて適宜選定すればよく、シリコン基板以外の半導体基板（例えば、ＧａＡｓ基板、ＩｎＰ基板、ＳｉＣ基板など）や、所謂ＳＯＩ基板などを用いてもよいし、絶縁性基板を用いて当該絶縁性基板自体が絶縁層２を構成するようにしてもよい。   In the above-described embodiment, a silicon substrate is used as the substrate 1, but the substrate 1 may be appropriately selected according to the specifications of the carbon nanotube application device, and a semiconductor substrate other than the silicon substrate (for example, a GaAs substrate, InP). Substrate, SiC substrate, etc.), a so-called SOI substrate, or the like may be used, or the insulating substrate itself may constitute the insulating layer 2 using an insulating substrate.

実施形態のカーボンナノチューブの製造方法を説明するための主要工程断面図である。It is a main process sectional view for explaining a manufacturing method of a carbon nanotube of an embodiment. 同上におけるカーボンナノチューブの他の製造方法を説明するための主要工程断面図である。It is a main process sectional view for explaining another manufacturing method of the carbon nanotube same as the above. 従来例のカーボンナノチューブの製造方法を説明するための主要工程平面図である。It is a main process top view for demonstrating the manufacturing method of the carbon nanotube of a prior art example.

符号の説明Explanation of symbols

１ 基板
２ 絶縁層
３ 触媒金属薄膜
３ａ 触媒部
３ｂ 触媒部
４ カーボンナノチューブ DESCRIPTION OF SYMBOLS 1 Substrate 2 Insulating layer 3 Catalytic metal thin film 3a Catalyst part 3b Catalyst part 4 Carbon nanotube

Claims (6)

基板の一表面側に触媒金属材料からなる触媒金属薄膜を形成する薄膜形成工程と、前記触媒金属薄膜を酸素を含む雰囲気中で溶融させてから冷却することによって前記触媒金属薄膜を複数の粒子状の触媒部に細分化する細分化工程と、細分化工程にて形成された各触媒部を加熱して当該各触媒部をより小さなサイズの複数の微粒子状の触媒部に再細分化する再細分化工程と、再細分化工程の後で熱ＣＶＤ法によって微粒子状の触媒部からカーボンナノチューブを成長させるカーボンナノチューブ成長工程とを備えることを特徴とするカーボンナノチューブの製造方法。   A thin film forming step of forming a catalytic metal thin film made of a catalytic metal material on one surface side of the substrate, and the catalytic metal thin film is cooled in a plurality of particles by cooling the catalytic metal thin film in an oxygen-containing atmosphere. Subdivision process for subdividing into catalyst parts, and re-subdivision for heating each catalyst part formed in the subdivision process and subdividing each catalyst part into a plurality of smaller-sized catalyst parts And a carbon nanotube growth step of growing the carbon nanotubes from the particulate catalyst portion by a thermal CVD method after the re-subdividing step. 前記細分化工程では、前記触媒金属薄膜を溶融させる際の雰囲気を酸素ガス雰囲気とすることを特徴とする請求項１記載のカーボンナノチューブの製造方法。   The method for producing carbon nanotubes according to claim 1, wherein, in the subdividing step, an atmosphere when melting the catalytic metal thin film is an oxygen gas atmosphere. 前記薄膜形成工程では、前記触媒金属薄膜の膜厚を量子サイズ効果により融点低下が起こる値に設定し、前記細分化工程では、前記触媒金属薄膜を溶融させる際に前記触媒金属材料の融点よりも低い温度で前記触媒金属薄膜を溶融させることを特徴とする請求項１または請求項２記載のカーボンナノチューブの製造方法。   In the thin film forming step, the film thickness of the catalytic metal thin film is set to a value at which the melting point lowers due to the quantum size effect, and in the subdividing step, the melting point of the catalytic metal material is higher than the melting point of the catalytic metal material. The method for producing carbon nanotubes according to claim 1 or 2, wherein the catalytic metal thin film is melted at a low temperature. 前記カーボンナノチューブ成長工程では、前記カーボンナノチューブの成長温度を前記再細分化工程における加熱温度と同じ温度に設定することを特徴とする請求項１ないし請求項３のいずれかに記載のカーボンナノチューブの製造方法。   The carbon nanotube production process according to any one of claims 1 to 3, wherein, in the carbon nanotube growth step, the growth temperature of the carbon nanotube is set to the same temperature as the heating temperature in the re-segmentation step. Method. 前記触媒金属材料として、Ｆｅ，Ｃｏ，Ｎｉ，Ｐｔ，Ｍｏの群から選択される１種類の材料を用いることを特徴とする請求項１ないし請求項４のいずれかに記載のカーボンナノチューブの製造方法。   The method for producing a carbon nanotube according to any one of claims 1 to 4, wherein one material selected from the group consisting of Fe, Co, Ni, Pt, and Mo is used as the catalytic metal material. . 前記薄膜形成工程の前に前記基板の前記一表面側に前記カーボンナノチューブ成長工程における前記触媒部の触媒効果を抑制する触媒効果抑制層を形成する触媒効果抑制層形成工程を備え、前記薄膜形成工程では、前記触媒効果抑制層上に前記触媒金属薄膜を形成するようにし、前記触媒金属材料がＦｅであり、前記触媒効果抑制層が少なくとも前記触媒金属薄膜の下地となるＭｏ層からなることを特徴とする請求項１ないし請求項５のいずれかに記載のカーボンナノチューブの製造方法。 The thin film forming step includes a catalytic effect suppressing layer forming step of forming a catalytic effect suppressing layer for suppressing the catalytic effect of the catalyst part in the carbon nanotube growth step on the one surface side of the substrate before the thin film forming step. So to so that to form the catalytic metal film on the catalytic effect inhibiting layer, wherein a catalyst metal material Fe, in that it consists of the Mo layer in which the catalytic effect suppressing layer serving as a base of at least the catalytic metal film method for producing a carbon nanotube according to any one of claims 1 to 5, characterized.
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