JP6212598B2 - Method for forming Fe fine particles for carbon fiber growth - Google Patents

Method for forming Fe fine particles for carbon fiber growth Download PDF

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JP6212598B2
JP6212598B2 JP2016107353A JP2016107353A JP6212598B2 JP 6212598 B2 JP6212598 B2 JP 6212598B2 JP 2016107353 A JP2016107353 A JP 2016107353A JP 2016107353 A JP2016107353 A JP 2016107353A JP 6212598 B2 JP6212598 B2 JP 6212598B2
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拓治 小向
拓治 小向
温 下元
温 下元
博之 永森
博之 永森
久美子 吉原
久美子 吉原
勉 中井
勉 中井
一久 石井
一久 石井
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Nitta Corp
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本発明は、炭素含有ガスに接触反応してカーボンナノチューブ(CNT)等のカーボンファイバを成長させる際の成長起点となるFe微粒子を基板上に形成する方法に関するものである。 The present invention relates to Fe fine particles comprising the growth starting point for growing the carbon fibers such as carbon nanotubes (CNT) in contact in response to the carbon-containing gas to how to form on the substrate.

CNTは、その性状、サイズ等により、各種用途が期待されている物質である。CNTの製造方法の一つに、炭素含有ガスに接触反応する触媒膜が成膜された触媒構造を有する基板を用いる方法がある。この触媒構造には、基板上にCNTの成長に対する触媒作用を持たないアルミニウム等の非触媒金属からなる助触媒金属膜(下地膜)と、この助触媒金属膜上の鉄等の触媒金属膜との2層(助触媒金属膜/触媒金属膜)構造としたものがある。このような2層構造では熱アニール処理を施すことで、上層の触媒金属膜を微粒子(触媒金属微粒子)化する。そして、この触媒金属微粒子に炭素含有ガスを接触反応させてCNTを成長させることで、当該触媒金属微粒子をCNTの成長起点とすることができるようになっている(特許文献1参照)。   CNT is a substance that is expected to be used for various purposes depending on its properties, size, and the like. One of the methods for producing CNTs is a method using a substrate having a catalyst structure on which a catalyst film that reacts with a carbon-containing gas is formed. The catalyst structure includes a promoter metal film (underlayer film) made of a non-catalyst metal such as aluminum that does not have a catalytic action on the growth of CNTs on the substrate, and a catalyst metal film such as iron on the promoter metal film, 2 layers (promoter metal film / catalyst metal film) structure. In such a two-layer structure, the upper catalyst metal film is made into fine particles (catalyst metal fine particles) by performing a thermal annealing treatment. Then, the catalytic metal fine particles are brought into contact with a carbon-containing gas to grow CNTs, whereby the catalytic metal fine particles can be used as the starting point of CNT growth (see Patent Document 1).

特開2001−303250号公報JP 2001-303250 A

本願出願人は、上記触媒構造に関して研究を行った。この研究を、図7および図8を参照して、説明する。この説明では、助触媒金属をAl、触媒金属をFeとした例を挙げる。図7において、50は基板、52はバリア膜、54は触媒膜である。   The applicant of the present application has studied the above catalyst structure. This study will be described with reference to FIGS. In this description, an example is given in which the promoter metal is Al and the catalyst metal is Fe. In FIG. 7, 50 is a substrate, 52 is a barrier film, and 54 is a catalyst film.

そして、Fe絶対量が過剰に設定された場合、図7(a)で示すように、触媒膜54は下層側にAl層54a、中間側にFe/Al合金層54b、上層側にFe飽和Al層54c、最上層側にFe層54dとなり、熱アニール処理では図7(b)で示すように、基板上最表面にFeが凝集して粒径不均一なFe微粒子(触媒金属微粒子)54eが生成され、このFe微粒子54eの粒径不均一により、図7(c)で示すように、Fe微粒子54eを成長起点とするCNT56も直径不均一に成長する結果となる。   When the absolute amount of Fe is set excessively, as shown in FIG. 7A, the catalyst film 54 has an Al layer 54a on the lower layer side, an Fe / Al alloy layer 54b on the middle side, and Fe saturated Al on the upper layer side. The layer 54c becomes the Fe layer 54d on the uppermost layer side, and in the thermal annealing treatment, as shown in FIG. Due to the generated non-uniform particle size of the Fe fine particles 54e, as shown in FIG. 7C, the CNTs 56 starting from the Fe fine particles 54e also grow non-uniformly in diameter.

また、Fe絶対量が少なく設定された場合、図8(a)で示すように、触媒膜54は下層側にAl層54f、上層側にFe/Al合金層54gとなり、熱アニール処理では図8(b)で示すように、Al層54f中に直径均一なFe微粒子54hが生成されても、そのほとんどの粒子はAl層54f中から表面へ析出していないため、Fe微粒子54hは炭素含有ガスに接触できないから、CNTは高密度に成長しない結果となる。   Further, when the Fe absolute amount is set to be small, as shown in FIG. 8A, the catalyst film 54 becomes the Al layer 54f on the lower layer side and the Fe / Al alloy layer 54g on the upper layer side. As shown in (b), even if Fe fine particles 54h having a uniform diameter are generated in the Al layer 54f, most of the particles are not deposited on the surface from the Al layer 54f. As a result, the CNT does not grow at a high density.

以上から、助触媒金属に対して触媒金属を過剰に設定すると、熱アニール処理の初期段階から後期段階に至る過程で触媒膜最表面にCNT成長核としての触媒金属微粒子が生成されてしまう結果、基板上最表面には触媒金属微粒子が粒径不均一に露出生成され、触媒金属微粒子を成長起点とするCNTも直径不均一に生成されてしまう。また、非触媒金属に対する触媒金属の比率が高いことで、基板上最表面での触媒効果が低下して炭素のアモルファス堆積が促進されて、CNTの成長が阻害されてしまう結果となる。   From the above, when the catalyst metal is excessively set with respect to the promoter metal, catalyst metal fine particles as CNT growth nuclei are generated on the outermost surface of the catalyst film in the process from the initial stage to the late stage of the thermal annealing treatment. The catalyst metal fine particles are exposed and formed on the outermost surface of the substrate with non-uniform particle sizes, and the CNTs having the catalyst metal fine particles as growth starting points are also generated with non-uniform diameters. In addition, since the ratio of the catalytic metal to the non-catalytic metal is high, the catalytic effect on the outermost surface on the substrate is lowered, the amorphous deposition of carbon is promoted, and the CNT growth is inhibited.

一方、助触媒金属に対して触媒金属が少なく設定されると、助触媒金属と触媒金属とが合金化し、触媒膜最表面に触媒金属微粒子がほとんど生成されず、大半の粒子が助触媒金属中に埋没した状態で触媒金属微粒子が生成されてCNTを生成することができなくなる。   On the other hand, when the catalyst metal is set to be less than the promoter metal, the promoter metal and the catalyst metal are alloyed, so that almost no catalyst metal fine particles are generated on the outermost surface of the catalyst film, and most of the particles are in the promoter metal. The catalyst metal fine particles are generated in a state of being buried in the metal, and CNT cannot be generated.

したがって、本発明は、助触媒金属に対して触媒金属を少なく設定しても、また、従来と比較して、最表面に粒径均一に触媒金属微粒子を析出させることができるようにすることで、助触媒金属に対する触媒金属の量の過不足に起因する上記課題を解消しようとしたものである。   Therefore, the present invention enables the catalyst metal fine particles to be deposited on the outermost surface with a uniform particle size even when the amount of the catalyst metal is set to be smaller than that of the promoter metal. The present invention has been made to solve the above-mentioned problems caused by excess and deficiency of the amount of catalyst metal relative to the promoter metal.

本発明によるカーボンファイバ成長用Fe微粒子形成方法は、基板上に、膜中に酸素を含ませながら炭素含有ガスに非反応の助触媒金属膜を形成する第1工程と、前記助触媒金属膜上に、Fe膜を形成する第2工程と、前記第2工程後に、前記基板に対して熱アニール処理を施すことで、前記基板上最表面に炭素含有ガスに接触反応するFe微粒子を析出させる第工程と、を含むことを特徴とするものである。 Fe microparticle formation method for a carbon fiber growth by the present invention comprises a base plate, a first step of forming a promoter metal film non-reactive carbon-containing gas while containing oxygen in the film, the promoter metal film above, a second step of forming a Fe film, after the second step, by applying a thermal annealing treatment, to precipitate Fe particles that contact reaction to a carbon-containing gas to the substrate on the top surface to the substrate And a third step.

上記工程で非金属元素を真空チャンバ内に導入する形態はガスに限定されず、酸による導入、スパッタによる導入等がある。上記非金属元素は好ましくは酸素、硫黄等である。助触媒金属は好ましくは非磁性金属である。非磁性金属としては、アルミニウム、銅、亜鉛等が好ましい。触媒金属は好ましくは磁性金属である。磁性金属は、鉄、ニッケル、コバルト等が好ましい。なお、非磁性金属と磁性金属との関係は、前者が助触媒金属、後者が触媒金属の関係になりやすい。   The form in which the nonmetallic element is introduced into the vacuum chamber in the above process is not limited to gas, and introduction by acid, introduction by sputtering, and the like. The nonmetallic element is preferably oxygen, sulfur or the like. The promoter metal is preferably a nonmagnetic metal. As the nonmagnetic metal, aluminum, copper, zinc and the like are preferable. The catalytic metal is preferably a magnetic metal. The magnetic metal is preferably iron, nickel, cobalt or the like. Note that the relationship between the nonmagnetic metal and the magnetic metal tends to be a promoter metal and the latter a catalyst metal.

本発明の基板は、最表層に非金属元素含有の助触媒金属膜を有するものである。   The substrate of the present invention has a non-metal element-containing promoter metal film on the outermost layer.

基板の素材は、特に限定されないが、シリコン、クロム、銅、タングステン、アルミニウム等、およびステンレス、インコネル等の合金、さらにはAl23、SiC等のセラミックスを例示することができる。 The material of the substrate is not particularly limited, and examples thereof include silicon, chromium, copper, tungsten, aluminum and the like, alloys such as stainless steel and inconel, and ceramics such as Al 2 O 3 and SiC.

基板上の触媒金属微粒子により成長するカーボンファイバは、その種類に特に限定されないが、CNT、グラファイトナノファイバ、カーボンナノホーン、カーボンナノコーン、カーボンナノバンブ等を例示することができる。   The carbon fiber grown by the catalytic metal fine particles on the substrate is not particularly limited, and examples thereof include CNT, graphite nanofiber, carbon nanohorn, carbon nanocone, and carbon nanobump.

本発明によれば、助触媒金属中に非金属元素を含ませるので、助触媒金属に対して触媒金属を少なく設定しても、熱アニール処理により、従来と比較して、最表面に触媒金属微粒子をほぼ粒径均一に析出させることができるようになる結果、助触媒金属に対する触媒金属の量的過不足に起因した上記課題を解消できるようになる。   According to the present invention, since the non-metallic element is contained in the promoter metal, even if the catalyst metal is set to be small relative to the promoter metal, the catalyst metal is formed on the outermost surface by the thermal annealing treatment as compared with the conventional case. As a result of allowing the fine particles to be deposited almost uniformly, it is possible to solve the above-mentioned problem caused by the excess or shortage of the catalytic metal relative to the promoter metal.

図1(a)は本発明の実施の形態にかかる触媒金属微粒子形成方法において熱アニール処理前の基板の構成を示す図、図1(b)はバリア膜上にAl膜を形成し、その形成において酸素を導入する工程を示す図、図1(c)はFeを蒸着原料としてバリア膜上にAl/Fe合金膜を生成する工程を示す図、図1(d)はAl/Fe合金膜上にFe微粒子を析出する工程を示す図、図1(e)はFe微粒子上にCNTを成長させる工程を示す図である。FIG. 1A is a diagram showing the structure of a substrate before thermal annealing in the method for forming catalytic metal fine particles according to the embodiment of the present invention, and FIG. 1B is a diagram showing the formation of an Al film on the barrier film. FIG. 1 (c) is a diagram showing a step of forming an Al / Fe alloy film on the barrier film using Fe as a deposition material, and FIG. 1 (d) is a diagram on the Al / Fe alloy film. FIG. 1E is a diagram showing a step of growing CNTs on the Fe fine particles. 図2(a)ないし図2(e)は、本発明の実施の形態にかかる触媒金属微粒子形成方法により製造した基板を用いてCNTを成膜させた場合の各SEM写真図である。2 (a) to 2 (e) are SEM photographs when CNTs are formed using a substrate manufactured by the catalytic metal fine particle forming method according to the embodiment of the present invention. 図3は最上層にAl膜を成膜してある基板の構成を示す図である。FIG. 3 is a diagram showing a configuration of a substrate on which an Al film is formed as the uppermost layer. 図4(a)は図3の基板を用いて酸素導入した場合の基板表面のSEM写真を示す図、図4(b)は図4(a)のCNT生成の概念を示す図である。4A is a diagram showing an SEM photograph of the substrate surface when oxygen is introduced using the substrate of FIG. 3, and FIG. 4B is a diagram showing the concept of CNT generation in FIG. 4A. 図5(a)は図3の基板を用いて酸素導入無しで高真空状態での基板表面のSEM写真を示す図、図5(b)は図5(a)の基板表面の状態を概念的に示す図である。FIG. 5A is a diagram showing an SEM photograph of the substrate surface in a high vacuum state without introducing oxygen using the substrate of FIG. 3, and FIG. 5B conceptually shows the state of the substrate surface of FIG. 5A. FIG. 図6はAl膜中のFe成膜位置の違いとFe微粒子化位置を示す図であり、図6(a1)ないし(e1)は、基板表面に触媒膜が成膜されている場合を示す図、図6(a2)ないし(e2)は、基板を熱アニール処理した場合のFe微粒子の析出状態を示す図である。FIG. 6 is a diagram showing a difference in Fe film formation position in the Al film and a position where Fe fine particles are formed, and FIGS. 6A1 to 6E1 are diagrams showing a case where a catalyst film is formed on the substrate surface. FIGS. 6A2 to 6E2 are views showing the precipitation state of Fe fine particles when the substrate is thermally annealed. 図7(a)(b)(c)はFe絶対量が多い場合の基板表面の状態を概念的に示す図である。FIGS. 7A, 7B, and 7C are diagrams conceptually showing the state of the substrate surface when the absolute amount of Fe is large. 図8(a)(b)はFe絶対量が少ない場合の基板表面の状態を概念的に示す図である。FIGS. 8A and 8B are diagrams conceptually showing the state of the substrate surface when the absolute amount of Fe is small.

以下、添付した図面を参照して、本発明の実施の形態に係る触媒金属微粒子形成方法を説明する。図1は同方法の工程を示す。同方法の実施においては図示略のEB−PVD(電子ビーム物理蒸着)装置におけるチャンバを用いる。EB−PVD装置は、周知されるように、高真空中で高エネルギーの電子ビーム(EB)を蒸着原料に照射し、この蒸着原料を加熱蒸気化させて基板表面に蒸着させることにより同原料による成膜を行う装置である。この成膜を行うための上記チャンバ内部は高真空下におかれる。この方法に用いる基板表面にはバリア膜が形成されている。   Hereinafter, a method for forming catalytic metal fine particles according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows the steps of the method. In the implementation of this method, a chamber in an EB-PVD (electron beam physical vapor deposition) apparatus (not shown) is used. As is well known, the EB-PVD apparatus uses an electron beam (EB) of high energy in a high vacuum to irradiate the deposition material, and the deposition material is heated and vaporized to be deposited on the substrate surface. An apparatus for forming a film. The inside of the chamber for performing this film formation is placed under a high vacuum. A barrier film is formed on the substrate surface used in this method.

図1(a)は図示略のチャンバ内に配置される基板2を示す。この基板2の表面にはバリア膜4が形成されている。本発明は基板2表面にバリア膜4が形成されていることには限定されず、バリア膜4が形成されていない基板2も含む。   FIG. 1A shows a substrate 2 arranged in a chamber (not shown). A barrier film 4 is formed on the surface of the substrate 2. The present invention is not limited to the formation of the barrier film 4 on the surface of the substrate 2 and includes the substrate 2 on which the barrier film 4 is not formed.

そして、図1(b)で示すように、EB−PVD装置における蒸着原料として炭素含有ガスに非反応の助触媒金属であるAlを用いて基板2表面にはバリア膜4を介してAl膜6を形成する。この場合、Al膜6中に非金属元素として酸素8を含ませる。酸素8の導入量は、好ましくは、チャンバ内圧力換算として10-5Paないし10-2Paである。次いで、次の蒸着原料として触媒金属であるFeを用いる。この場合、蒸着原料であるFeの絶対量を少なく制御する。これにより、図1(c)で示すように、バリア膜4上にAlとFeとの合金であるAl/Fe合金膜10を形成する。この場合、Al/Fe合金膜10の膜厚制御により、次に説明するFe微粒子12の粒径を制御することができる。なお、実施の形態では基板2上での成膜にEB−PVD装置を用いたが、これに限定されず、スパッタ装置、熱CVD装置、その他の成膜装置を用いて基板2上に成膜することができる。 Then, as shown in FIG. 1B, Al, which is a co-catalyst metal that does not react with the carbon-containing gas, is used as an evaporation source in the EB-PVD apparatus, and an Al film 6 is formed on the surface of the substrate 2 via a barrier film 4. Form. In this case, oxygen 8 is included in the Al film 6 as a nonmetallic element. The amount of oxygen 8 introduced is preferably 10 −5 Pa to 10 −2 Pa in terms of chamber internal pressure. Next, Fe as a catalyst metal is used as the next vapor deposition material. In this case, the absolute amount of Fe as a deposition raw material is controlled to be small. Thereby, as shown in FIG. 1C, an Al / Fe alloy film 10 which is an alloy of Al and Fe is formed on the barrier film 4. In this case, by controlling the film thickness of the Al / Fe alloy film 10, the particle diameter of the Fe fine particles 12 described below can be controlled. In the embodiment, the EB-PVD apparatus is used for film formation on the substrate 2. However, the present invention is not limited to this, and the film formation is performed on the substrate 2 using a sputtering apparatus, a thermal CVD apparatus, or another film formation apparatus. can do.

こうしてAl/Fe合金膜10を形成すると、チャンバ内の温度制御で熱アニール処理を行う。この熱アニール処理を行うと、図1(d)で示すように、Al/Fe合金膜10中からFe微粒子12が析出する。この熱アニール処理は常温から徐々に昇温して熱アニール処理を行ってもよいし、一定温度で熱アニール処理してもよい。この熱アニール処理温度はAl/Fe合金膜10が蒸発しない温度以下であることが好ましい。このようにAl/Fe合金膜10からFe微粒子12を析出させることができるのは上記において酸素8を導入していることによる。この場合、熱アニール処理の初期段階でのみAl/Fe合金膜10の表面にFe微粒子12が形成される結果として、Fe微粒子12の粒径を、ほぼ均一に制御することができる。   When the Al / Fe alloy film 10 is thus formed, thermal annealing is performed by controlling the temperature in the chamber. When this thermal annealing treatment is performed, Fe fine particles 12 are precipitated from the Al / Fe alloy film 10 as shown in FIG. The thermal annealing treatment may be performed by gradually raising the temperature from room temperature, or may be performed at a constant temperature. The thermal annealing temperature is preferably equal to or lower than the temperature at which the Al / Fe alloy film 10 does not evaporate. The reason why the Fe fine particles 12 can be precipitated from the Al / Fe alloy film 10 is that oxygen 8 is introduced in the above. In this case, as a result of forming the Fe fine particles 12 on the surface of the Al / Fe alloy film 10 only at the initial stage of the thermal annealing treatment, the particle size of the Fe fine particles 12 can be controlled almost uniformly.

以上から、基板上最表面にFe微粒子12を形成させると、Fe微粒子12上にCNTを成長させるため、チャンバ内に炭素含有ガスを導入する。そうすると、炭素含有ガスがFe微粒子12に接触反応し、図1(e)で示すように、Fe微粒子12上にCNT14が成長する。この場合、Fe微粒子12の粒径が均一化されていることにより、CNT14をその直径を均一化させて成長させることができるようになる。   From the above, when the Fe fine particles 12 are formed on the outermost surface of the substrate, the carbon-containing gas is introduced into the chamber in order to grow CNTs on the Fe fine particles 12. Then, the carbon-containing gas contacts and reacts with the Fe fine particles 12, and the CNTs 14 grow on the Fe fine particles 12, as shown in FIG. In this case, since the particle diameter of the Fe fine particles 12 is made uniform, the CNT 14 can be grown with the diameter made uniform.

図2(a)ないし図2(e)のSEM写真では上記酸素導入量を圧力換算で10-5Paから10-2Paの範囲で種々に変更して図示略の真空チャンバ内に酸素を微量に存在させた場合において、Fe微粒子12上でのCNT14の成長の違いを示している。また、これらSEM写真においては、CNT製造の一例として基板2を700℃に加熱し、炭素含有ガスとしてアセチレンガスを200SCCM導入し、真空チャンバ内圧を200Paで30分間保持して、CNT14を成長させたSEM写真である。 In the SEM photographs of FIGS. 2 (a) to 2 (e), the oxygen introduction amount is variously changed in the range of 10 −5 Pa to 10 −2 Pa in terms of pressure, and a small amount of oxygen is introduced into a vacuum chamber (not shown). The difference in the growth of the CNTs 14 on the Fe fine particles 12 is shown. In these SEM photographs, the substrate 2 was heated to 700 ° C. as an example of CNT production, acetylene gas was introduced at 200 SCCM as a carbon-containing gas, and the internal pressure of the vacuum chamber was maintained at 200 Pa for 30 minutes to grow CNT 14. It is a SEM photograph.

図2(a)では、酸素導入量を圧力換算で5×10-5Paとして、Al膜6中に非金属元素として酸素8を含ませてFe微粒子12を生成し、このFe微粒子12でCNT14を成長させた場合のSEM写真であり、このSEM写真ではCNT14の成長長さは1.6μmである。 In FIG. 2A, the amount of oxygen introduced is 5 × 10 −5 Pa in terms of pressure, and Fe fine particles 12 are generated by including oxygen 8 as a nonmetallic element in the Al film 6. Is a SEM photograph in the case of growing CNT14, and in this SEM photograph, the growth length of the CNT 14 is 1.6 μm.

図2(b)では、酸素導入量を圧力換算で2×10-4Paとして、Al膜6中に非金属元素として酸素8を含ませてFe微粒子12を生成し、このFe微粒子12でCNT14を成長させた場合のSEM写真であり、このSEM写真ではCNT14の成長長さは450μmである。 In FIG. 2B, the oxygen introduction amount is set to 2 × 10 −4 Pa in terms of pressure, and Fe fine particles 12 are generated by including oxygen 8 as a nonmetallic element in the Al film 6. Is a SEM photograph in the case of growing CNT14, and in this SEM photograph, the growth length of the CNT 14 is 450 μm.

図2(c)では、酸素導入量を圧力換算で5×10-4Paとして、Al膜6中に非金属元素として酸素8を含ませてFe微粒子12を生成し、このFe微粒子12でCNT14を成長させた場合のSEM写真であり、このSEM写真ではCNT14の成長長さは350μmであることを示す。 In FIG. 2C, the amount of oxygen introduced is 5 × 10 −4 Pa in terms of pressure, and Fe fine particles 12 are generated by including oxygen 8 as a nonmetallic element in the Al film 6. Is a SEM photograph when the CNTs are grown, and this SEM photograph shows that the growth length of the CNT 14 is 350 μm.

図2(d)では、酸素導入量を圧力換算で2×10-3Paとして、Al膜6中に非金属元素として酸素8を含ませてFe微粒子12を生成し、このFe微粒子12でCNT14を成長させた場合のSEM写真であり、このSEM写真ではCNT14の成長長さは70μmである。 In FIG. 2D, the oxygen introduction amount is set to 2 × 10 −3 Pa in terms of pressure, and the Fe fine particles 12 are generated by including oxygen 8 as a nonmetallic element in the Al film 6. Is a SEM photograph in the case of growing CNT14, and in this SEM photograph, the growth length of the CNT 14 is 70 μm.

図2(e)では、酸素導入量を圧力換算で5×10-3Paとして、Al膜6中に非金属元素として酸素8を含ませてFe微粒子12を生成し、このFe微粒子12でCNT14を成長させた場合のSEM写真であり、このSEM写真ではCNT14の成長長さは100μm程度である。 In FIG. 2E, the amount of oxygen introduced is 5 × 10 −3 Pa in terms of pressure, and Fe fine particles 12 are generated by including oxygen 8 as a nonmetallic element in the Al film 6. In this SEM photograph, the growth length of the CNT 14 is about 100 μm.

以上から、これら図2(a)ないし図2(e)のうち、特に図2(c)では複数のCNT14が高密度で直径均一でかつ長尺でかつ優れた直線性で成長している。このことから、酸素の導入圧力制御により、上記のようにCNTを成長させることができることが判る。   From the above, among these FIGS. 2 (a) to 2 (e), particularly in FIG. 2 (c), a plurality of CNTs 14 are grown with a high density, a uniform diameter, a long length and excellent linearity. This shows that CNT can be grown as described above by controlling the oxygen introduction pressure.

図3で示す基板(シリコン基板)16においては、基板16上に、自然酸化膜(SiO2)18、バリア膜(Al23)20、膜厚40ÅのAl膜22、膜厚22ÅのFe膜24、膜厚10ÅのAl膜26が、この順で形成されている。そして、図3で示す基板16を用いて、図4(a)のSEM写真では最上層のAl膜26に酸素を圧力換算2×10-3Paで導入したことでCNTが200μm長さに成長していることを示す。また、図4(b)では図4(a)に対応し、酸素導入によりAl膜26上に粒径均一にFe微粒子28が析出し、この粒径均一なFe微粒子28により、直径均一にCNT29が成長する様子を概念的に示している。また、図3で示す基板16を用いて、図5(a)のSEM写真では最上層のAl膜26に酸素を導入せず、高真空下に置いたことでCNTが成長していない状態を示し、図5(b)には図5(a)に対応し、酸素を上記導入しないことにより、Al膜26中にFe微粒子28が析出し、CNTが成長していない状態を示す。 In the substrate (silicon substrate) 16 shown in FIG. 3, a natural oxide film (SiO 2 ) 18, a barrier film (Al 2 O 3 ) 20, an Al film 22 with a thickness of 40 mm, and an Fe film with a thickness of 22 mm are formed on the substrate 16. A film 24 and an Al film 26 having a thickness of 10 mm are formed in this order. Then, using the substrate 16 shown in FIG. 3, in the SEM photograph of FIG. 4A, CNT grows to a length of 200 μm by introducing oxygen into the uppermost Al film 26 at a pressure conversion of 2 × 10 −3 Pa. Indicates that 4 (b) corresponds to FIG. 4 (a), and by introducing oxygen, Fe fine particles 28 are deposited on the Al film 26 with a uniform particle size. Conceptually shows the growth of. Further, in the SEM photograph of FIG. 5A, oxygen is not introduced into the uppermost Al film 26 and the CNT is not grown by placing it under a high vacuum using the substrate 16 shown in FIG. FIG. 5B shows a state corresponding to FIG. 5A, in which Fe fine particles 28 are precipitated in the Al film 26 and CNT is not grown by not introducing oxygen.

この図3ないし図5から、最上層を非触媒金属であるAl膜26で覆っても、上記酸素導入により、Al膜26表面には下層側のFe膜24からFe微粒子28が析出し、触媒膜として機能させられることが判る。また、酸素を導入しない場合は、Al膜26表面には下層側のFe膜24からFe微粒子28が析出せず、触媒膜として機能させられないことが判る。   3 to 5, even if the uppermost layer is covered with an Al film 26 which is a non-catalytic metal, Fe fine particles 28 are deposited on the surface of the Al film 26 from the Fe film 24 on the lower layer side due to the introduction of oxygen. It can be seen that it can function as a membrane. Further, it can be seen that when oxygen is not introduced, Fe fine particles 28 do not precipitate from the lower layer Fe film 24 on the surface of the Al film 26 and cannot function as a catalyst film.

図6を参照して、Al膜中のFe成膜位置の違いによるFe微粒子化位置を説明する。図6(a1)は、基板30表面のバリア膜32上に、膜厚50ÅのAl膜34と、膜厚22ÅのFe膜36とがこの順で成膜されている様子を示す。この図6(a1)で示す基板30を熱アニール処理すると、図6(a2)で示すように、最上層にはFe微粒子38が析出する。   With reference to FIG. 6, the Fe fine particle formation position by the difference in Fe film-forming position in Al film | membrane is demonstrated. FIG. 6A1 shows a state in which an Al film 34 having a thickness of 50 mm and an Fe film 36 having a thickness of 22 mm are formed in this order on the barrier film 32 on the surface of the substrate 30. When the substrate 30 shown in FIG. 6 (a1) is subjected to a thermal annealing treatment, Fe fine particles 38 are deposited on the uppermost layer as shown in FIG. 6 (a2).

図6(b1)は、基板30表面のバリア膜32上に、膜厚40ÅのAl膜34と、膜厚22ÅのFe膜36と、膜厚10ÅのAl膜40がこの順で成膜されている場合を示す。図6(a1)とは異なり、図6(b1)ではFe膜36上にAl膜40が成膜されている。このような基板30を熱アニール処理すると、図6(b2)で示すように、最上層の膜厚10ÅのAl膜40表面にはその下層側のFe膜36からFe微粒子42が析出する。   In FIG. 6B1, an Al film 34 having a thickness of 40 mm, an Fe film 36 having a thickness of 22 mm, and an Al film 40 having a thickness of 10 mm are formed in this order on the barrier film 32 on the surface of the substrate 30. Indicates the case. Unlike FIG. 6A1, an Al film 40 is formed on the Fe film 36 in FIG. 6B1. When such a substrate 30 is subjected to a thermal annealing treatment, as shown in FIG. 6 (b2), Fe fine particles 42 are deposited from the lower layer Fe film 36 on the surface of the uppermost Al film 40 having a thickness of 10 mm.

図6(c1)は、基板30表面のバリア膜32上に、膜厚25ÅのAl膜34と、膜厚22ÅのFe膜36と、膜厚25ÅのAl膜40が成膜されている場合を示す。図6(c1)では最上層のAl膜40の膜厚が図6(b1)の10Åよりも厚い25Åに設定されている。この基板30を熱アニール処理すると、図6(c2)で示すように、最上層のAl膜40表面にはその下層側のFe膜36からFe微粒子が析出しない。   FIG. 6C1 shows a case where an Al film 34 with a thickness of 25 mm, an Fe film 36 with a thickness of 22 mm, and an Al film 40 with a thickness of 25 mm are formed on the barrier film 32 on the surface of the substrate 30. Show. In FIG. 6C1, the thickness of the uppermost Al film 40 is set to 25 mm thicker than 10 mm in FIG. 6B1. When this substrate 30 is subjected to a thermal annealing treatment, as shown in FIG. 6C2, Fe fine particles are not deposited from the lower layer Fe film 36 on the surface of the uppermost Al film 40.

図6(d1)は、基板30表面のバリア膜32上に、膜厚10ÅのAl膜34と、膜厚22ÅのFe膜36と、膜厚40ÅのAl膜40が成膜されている場合を示す。このような基板30を熱アニール処理すると、図6(d2)で示すように、Al膜40の膜厚が厚すぎた結果、その表面には下層側のFe膜36からFe微粒子が析出しない。   FIG. 6D1 shows a case where an Al film 34 having a thickness of 10 mm, an Fe film 36 having a thickness of 22 mm, and an Al film 40 having a thickness of 40 mm are formed on the barrier film 32 on the surface of the substrate 30. Show. When such a substrate 30 is subjected to a thermal annealing treatment, as shown in FIG. 6 (d2), as a result of the film thickness of the Al film 40 being too thick, Fe fine particles are not deposited on the surface of the Fe film 36 on the lower layer side.

図6(e1)は、基板30表面のバリア膜32上に、Al膜は無く(膜厚0Å)、膜厚22ÅのFe膜36と、膜厚50ÅのAl膜40が成膜されている場合を示す。このような基板30を熱アニール処理すると、図6(e2)で示すように、Al膜40表面にFe微粒子が析出しない。   FIG. 6E1 shows a case where there is no Al film (thickness 0 mm), an Fe film 36 having a thickness of 22 mm, and an Al film 40 having a thickness of 50 mm are formed on the barrier film 32 on the surface of the substrate 30. Indicates. When such a substrate 30 is subjected to thermal annealing, Fe fine particles are not deposited on the surface of the Al film 40 as shown in FIG.

以上から、基板30表面のAl膜中にFe膜が成膜される場合において、Fe膜より上層側に存在するAl膜の膜厚が上限を超えて厚すぎるような場合では、Fe微粒子は析出することができなくなることが判る。このことから、最上層のAl膜の膜厚設定がFe微粒子の微粒子化位置に関係があることが判る。   From the above, when the Fe film is formed in the Al film on the surface of the substrate 30, the Fe fine particles are precipitated when the thickness of the Al film existing on the upper layer side of the Fe film is too thick beyond the upper limit. It turns out that it becomes impossible to do. From this, it can be seen that the thickness setting of the uppermost Al film is related to the atomization position of the Fe fine particles.

以上から本実施の形態では、非金属元素として酸素を助触媒金属中に導入するので、助触媒金属に対して触媒金属を少なく設定しても、最表面には触媒金属微粒子を粒径均一に析出させることができるようになり、結果として、直径均一にCNTを成長させることができる触媒金属微粒子形成方法を提供できると共に、その方法の実施に用いる基板を得ることができるようになる。   From the above, in the present embodiment, oxygen is introduced into the promoter metal as a non-metallic element. Therefore, even if the catalyst metal is set to a small amount with respect to the promoter metal, the catalyst metal fine particles are uniformly formed on the outermost surface. As a result, it is possible to provide a method for forming catalytic metal fine particles capable of growing CNTs uniformly in diameter, and to obtain a substrate used for carrying out the method.

そして、本実施の形態では、助触媒金属に対して触媒金属を必要最低量に設定しても、最表面から触媒金属微粒子を粒径均一に析出させることができ、また、そうした触媒金属微粒子の析出量も容易に制御できるようになる。   In the present embodiment, even if the catalyst metal is set to the minimum required amount with respect to the promoter metal, the catalyst metal fine particles can be deposited uniformly from the outermost surface. The amount of precipitation can also be easily controlled.

また、触媒金属微粒子が助触媒金属中に埋没しないから、CNTを高密度に成長させることができるようになる。   Further, since the catalyst metal fine particles are not buried in the promoter metal, CNTs can be grown at a high density.

さらに、助触媒金属に対して触媒金属を必要最低量に設定しても、最表面から触媒金属微粒子を粒径均一に析出させることができる結果、熱アニール処理の初期段階ではCNTの成長核の発生、後期段階ではその核の成長と制御とが可能となり、CNTの直径ばらつきを抑制できるようになる。   Furthermore, even if the catalyst metal is set to the minimum necessary amount with respect to the promoter metal, the catalyst metal fine particles can be uniformly deposited from the outermost surface. As a result, in the initial stage of the thermal annealing treatment, the growth nuclei of CNTs At the generation and late stage, the growth and control of the nucleus becomes possible, and the CNT diameter variation can be suppressed.

さらにまた、熱アニール処理後の助触媒金属中に含む触媒金属比率が低いことにより、非触媒金属表面での触媒能が失われる結果、カーボンのアモルファス堆積を防止し、結果、CNTの成長阻害要因を抑制制御できることで、長尺なCNTを得ることができるようになる。   Furthermore, the low catalytic metal ratio in the co-catalyst metal after the thermal annealing treatment results in loss of catalytic activity on the non-catalytic metal surface, thereby preventing carbon amorphous deposition, resulting in CNT growth inhibiting factors. As a result, it is possible to obtain long CNTs.

2 基板
4 バリア膜
6 Al膜
8 酸素
10 Al/Fe合金膜
12 Fe微粒子
14 CNT
2 Substrate 4 Barrier film 6 Al film 8 Oxygen 10 Al / Fe alloy film 12 Fe fine particle 14 CNT

Claims (4)

基板上に、膜中に酸素を含ませながら炭素含有ガスに非反応の助触媒金属膜を形成する第1工程と、
前記助触媒金属膜上に、Fe膜を形成する第2工程と、
前記第2工程後に、前記基板に対して熱アニール処理を施すことで、前記基板上最表面に炭素含有ガスに接触反応するFe微粒子を析出させる第3工程とを含み、
前記第1工程では、チャンバ内に、チャンバ内圧力換算で2×10 ‐4 Paないし5×10 ‐3 Paとして酸素を存在させて、前記助触媒金属膜の膜中に酸素を含ませる
ことを特徴とするカーボンファイバ成長用Fe微粒子形成方法。
A first step of forming a non-reacting promoter metal film on a carbon-containing gas while oxygen is included in the film on the substrate;
A second step of forming an Fe film on the promoter metal film;
After the second step, by applying a thermal annealing process, look including a third step of precipitating the Fe particles that contact reaction to a carbon-containing gas to the substrate on the top surface to the substrate,
In the first step, oxygen is present in the chamber as 2 × 10 −4 Pa to 5 × 10 −3 Pa in terms of the pressure in the chamber, and oxygen is included in the promoter metal film. A method for forming Fe fine particles for carbon fiber growth, characterized in that:
前記助触媒金属膜が非磁性金属を主構成とすることを特徴とする請求項1に記載のカーボンファイバ成長用Fe微粒子形成方法。   The method for forming Fe fine particles for carbon fiber growth according to claim 1, wherein the promoter metal film is mainly composed of a non-magnetic metal. 前記助触媒金属膜がAl膜であることを特徴とする請求項2に記載のカーボンファイバ成長用Fe微粒子形成方法。   3. The method for forming Fe fine particles for carbon fiber growth according to claim 2, wherein the promoter metal film is an Al film. 前記第2工程では、Al/Fe合金膜が形成されることを特徴とする請求項3に記載のカーボンファイバ成長用Fe微粒子形成方法。   The method of forming Fe fine particles for carbon fiber growth according to claim 3, wherein an Al / Fe alloy film is formed in the second step.
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