JP2005259600A - Efficient electronic emitter and its manufacturing method - Google Patents
Efficient electronic emitter and its manufacturing method Download PDFInfo
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- JP2005259600A JP2005259600A JP2004071438A JP2004071438A JP2005259600A JP 2005259600 A JP2005259600 A JP 2005259600A JP 2004071438 A JP2004071438 A JP 2004071438A JP 2004071438 A JP2004071438 A JP 2004071438A JP 2005259600 A JP2005259600 A JP 2005259600A
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本発明は、金属、半導体あるいはガラス、セラミック等の絶縁性基板上の金属薄膜上に分散された触媒超微粒子集団、あるいは触媒となる金属および非遷移金属が一定割合の超微粒子集団が選択的に形成されており、当該超微粒子上に長尺および高アスペクト比のカーボンナノチューブ群が形成されたことを特徴とする高効率電子エミッタおよびその製造方法に関する。 In the present invention, a catalyst ultrafine particle group dispersed on a metal thin film on an insulating substrate such as a metal, a semiconductor, glass, or ceramic, or an ultrafine particle group having a certain ratio of a metal and a non-transition metal as a catalyst is selectively used. The present invention relates to a high-efficiency electron emitter and a method of manufacturing the same, wherein a group of long and high aspect ratio carbon nanotubes are formed on the ultrafine particles.
従来、高効率電子エミッタとしてカーボンナノチューブやカーボンナノファイバー等の炭素系材料が注目され研究開発されてきた。なかでも、カーボンナノチューブはその大きいアスペクト比から優れた電子放出能を示すことから、分散法やＣＶＤ法を用いて商品化開発が行われている（例えば、特許文献１参照）。 Conventionally, carbon-based materials such as carbon nanotubes and carbon nanofibers have attracted attention and have been researched and developed as high-efficiency electron emitters. Among them, since carbon nanotubes exhibit excellent electron emission ability due to their large aspect ratio, commercial development has been carried out using a dispersion method or a CVD method (see, for example, Patent Document 1).
特に、カーボンナノチューブを基板に対し垂直方向に配置し、その大きいアスペクト比を生かし、ナノメートルサイズの尖った先端に電界を集中させ電子放出素子として利用するケースにおいては、電界集中を有効に生じさせるために、カーボンナノチューブを適切な密度で形成することが必要であることがコンピュータシミュレーションにより示された。 In particular, in the case where carbon nanotubes are arranged in a direction perpendicular to the substrate, taking advantage of the large aspect ratio and concentrating the electric field on a sharp tip with a nanometer size, the electric field concentration is effectively generated. Therefore, it has been shown by computer simulation that it is necessary to form carbon nanotubes with an appropriate density.
しかし、単体の通常の方法で得られる数μｍのカーボンナノチューブを最適に配置することによって得られる閾電圧は１〜２Ｖ／μｍ（１μＡ／ｃｍ２）、電流密度は２〜３Ｖ／μｍ（１ｍＡ／ｃｍ２）であり、電子放出電流密度ならびに閾電圧は不充分であった。
したがって、本発明においては、カーボンナノチューブ電子エミッタの閾電圧をより低下させ、かつ、より高い電流密度を得ることを課題とする。 Accordingly, it is an object of the present invention to further reduce the threshold voltage of the carbon nanotube electron emitter and obtain a higher current density.
本発明の高効率電子エミッタは、金属，半導体あるいは絶縁性基板上に選択的に形成された触媒となる微粒子集団と、該触媒微粒子集団に形成された高アスペクト比を有するカーボンナノチューブ群とを備えたものである。 The high-efficiency electron emitter of the present invention comprises a fine particle group that is a catalyst selectively formed on a metal, semiconductor, or insulating substrate, and a carbon nanotube group that is formed in the catalyst fine particle group and has a high aspect ratio. It is a thing.
カーボンナノチューブ群は、長さ１０μｍ以上でかつアスペクト比が１００００以上に形成されている。 The carbon nanotube group has a length of 10 μm or more and an aspect ratio of 10,000 or more.
触媒微粒子としては、少なくともＦｅおよびＦｅを含む化学物あるいは混合元素である。 The catalyst fine particles are chemicals or mixed elements containing at least Fe and Fe.
基板がＳｉであり、触媒微粒子がＡｌ薄膜上に形成したＦｅ薄膜を熱処理して得られるＦｅ／Ａｌであることを特徴とする請求項１に記載の高効率電子エミッタ。
本発明の高効率電子エミッタの製造方法は、基板上に金属薄膜を形成する工程と、前記金属薄膜上に触媒微粒子を形成する工程と、前記触媒微粒子をエッチングして集団形成する工程と、前記触媒微粒子集団に１０μｍ以上の長尺でかつアスペクト比が１００００以上のカーボンナノチューブ群を形成する工程とを含むものである。
The high-efficiency electron emitter according to claim 1, wherein the substrate is Si, and the catalyst fine particles are Fe / Al obtained by heat-treating an Fe thin film formed on an Al thin film.
The method for producing a high-efficiency electron emitter of the present invention includes a step of forming a metal thin film on a substrate, a step of forming catalyst fine particles on the metal thin film, a step of collectively forming the catalyst fine particles by etching, Forming a carbon nanotube group having a length of 10 μm or more and an aspect ratio of 10,000 or more in the catalyst fine particle population.
本発明の高効率電子エミッタおよびその製造方法によると、長尺カーボンナノチューブのアスペクト比の大きさを利用し、電子放出にかかわる先端部分の結晶性が良好なカーボンナノチューブが得られ、電子放出電流も大きくできる。 According to the high-efficiency electron emitter of the present invention and the manufacturing method thereof, a carbon nanotube having a good crystallinity at the tip portion related to electron emission can be obtained by utilizing the size of the aspect ratio of the long carbon nanotube, and the electron emission current is also reduced. Can be bigger.
また、パターン化による電界集中の促進により、電子放出サイトが大きいことと相まって、電子放出電流を大きくすることができる。 Further, by promoting the electric field concentration by patterning, the electron emission current can be increased in combination with the large electron emission site.
本発明によれば、カーボンナノチューブ電子エミッタの閾電圧をより低下させ、かつ、より高い電流密度を得ることができる。 According to the present invention, the threshold voltage of the carbon nanotube electron emitter can be further reduced and a higher current density can be obtained.
本発明の最良の実施形態を図１ないし図１３に基づいて説明する。
熱ＣＶＤ法による長尺のカーボンナノチューブの形成について述べる。
The best mode for carrying out the present invention will be described with reference to FIGS.
The formation of long carbon nanotubes by thermal CVD will be described.
表１に熱ＣＶＤの条件を示す。 Table 1 shows the conditions for thermal CVD.
基板としてはＳｉ基板を用い、Ｓｉ基板上に金属薄膜を形成し、かつ、金属薄膜上にマグネトロンスパッタリングにより、Ａｌを１０ｎｍ、Ｆｅを１０ｎｍ形成した基板を用いている。 As the substrate, a Si substrate is used, a metal thin film is formed on the Si substrate, and a substrate in which Al is formed to 10 nm and Fe is formed to 10 nm on the metal thin film by magnetron sputtering is used.
図１にカーボンナノチューブ成長前のＦｅ／Ａｌ触媒微粒子のＳＥＭ像を示す。 FIG. 1 shows an SEM image of Fe / Al catalyst fine particles before carbon nanotube growth.
図２に基板上に作成したカーボンナノチューブの断面ＳＥＭ像、図３に図２のカーボンナノチューブの断面ＳＥＭ像の先端部分の拡大図、図４に図２のカーボンナノチューブの断面ＳＥＭ像のボディ部分の拡大図を示す。 2 is a cross-sectional SEM image of the carbon nanotube prepared on the substrate, FIG. 3 is an enlarged view of the tip portion of the cross-sectional SEM image of the carbon nanotube in FIG. 2, and FIG. 4 is a body part of the cross-sectional SEM image of the carbon nanotube in FIG. An enlarged view is shown.
図５にＦｅ／Ａｌ／Ｓｉ上に作成した多層カーボンナノチューブのＴＥＭ像、図６に図５の多層カーボンナノチューブ構造のグラファイト層の拡大図を示す。 FIG. 5 shows a TEM image of the multi-walled carbon nanotube formed on Fe / Al / Si, and FIG. 6 shows an enlarged view of the graphite layer of the multi-walled carbon nanotube structure of FIG.
カーボンナノチューブは、長さ８０〜１４０μｍ、平均直径１０ｎｍ以下、密度１０１０／ｃｍ２である結晶性のよい多層カーボンナノチューブである、
図７，８に、カーボンナノチューブのパターン化について示す。基板上に形成した触媒をフォトリソグラフィにより、直径５０μｍ、ピッチ２５０μｍにてパターン化する。１０はカーボンナノチューブ群を示しており、各カーボンナノチューブの一本の長さは１２０μｍ、直径は１０ｎｍであり、アスペクト比は１２０００（＞１００００）となる。
The carbon nanotubes are multi-walled carbon nanotubes with good crystallinity having a length of 80 to 140 μm, an average diameter of 10 nm or less, and a density of 10 10 / cm 2 .
7 and 8 show the patterning of carbon nanotubes. The catalyst formed on the substrate is patterned by photolithography with a diameter of 50 μm and a pitch of 250 μm. Reference numeral 10 denotes a group of carbon nanotubes. Each carbon nanotube has a length of 120 μm, a diameter of 10 nm, and an aspect ratio of 12000 (> 10000).
図９に、パターン化されたカーボンナノチューブの電界電子放出特性を示す。横軸は電界Ｅ（Ｖ／μｍ）、縦軸は電子放出電流密度Ｊ（Ａ／ｃｍ２）を示している。図９より、ターンオン電界（１μＡ／ｃｍ２）としてＶｏｎ＝０．４Ｖ／μｍ、閾値電界（１ｍＡ／ｃｍ２）としてＶｔｈ＝０．７Ｖ／μｍという極めて優れたＥ−Ｊ特性を示す高効率電子エミッタ特性が得られることが明らかになった。 FIG. 9 shows the field electron emission characteristics of the patterned carbon nanotubes. The horizontal axis represents the electric field E (V / μm), and the vertical axis represents the electron emission current density J (A / cm 2 ). From FIG. 9, it is shown that the turn-on electric field (1 μA / cm 2 ) is V on = 0.4 V / μm and the threshold electric field (1 mA / cm 2 ) is Vth = 0.7 V / μm. It became clear that the electron emitter characteristic was obtained.
図１０に、パターン化された長尺カーボンナノチューブの電子放出像（対向する蛍光体塗布アノード上の発光パターン）を示している。
このようなパターン化による高効率化について理由を検討するため、電界電子放出特性（Ｆ−Ｎプロット）を調べた。図１１にその結果を示す。この結果より、パターン化ありの場合と、パターン化なしの場合の双方とも、Ｊ／Ｅ２−１／Ｅ特性は直線上に乗り、電界放出であることを示している。
FIG. 10 shows an electron emission image of a patterned long carbon nanotube (light emission pattern on the opposing phosphor-coated anode).
In order to examine the reason for high efficiency by such patterning, field electron emission characteristics (FN plot) were examined. FIG. 11 shows the result. This result shows that the J / E 2 -1 / E characteristic is on a straight line in both the case with patterning and the case without patterning, indicating field emission.
ただし、Ｆ−Ｎ式は、
ｌｎ（Ｊ／Ｅ２）＝ｌｎＡ−（１／Ｅ）・（Ｃ／β）
ここで、
Ａ＝１．５６×１０−６・β２／φ
Ｃ＝６．８３×１０９φ３／２
以下、仕事関数φ＝５ｅＶとしている。
However, the FN formula is
ln (J / E 2 ) = lnA− (1 / E) · (C / β)
here,
A = 1.56 × 10 −6 · β 2 / φ
C = 6.83 × 10 9 φ 3/2
Hereinafter, the work function φ = 5 eV.
パターン化ありの場合、Ｆ−Ｎ式から求めた電界集中因子β≒１４０００であり、パターン化なしの場合、β≒６０００であった。 In the case of patterning, the electric field concentration factor β≈14000 obtained from the FN equation, and in the case of no patterning, β≈6000.
以上のことから、パターン化による高効率化は、電解集中因子βの増大、電子放出サイトの増大、結晶性の向上等によることが判る。 From the above, it can be seen that the high efficiency by patterning is due to an increase in the electrolytic concentration factor β, an increase in electron emission sites, an improvement in crystallinity, and the like.
さらに、ガラス基板を用いるときに必要と考えられるプロセス温度の低温化について検討した。図１２に、成長温度５５０℃で直径５０μｍ、ピッチ１００μｍの低温合成パターン化カーボンナノチューブの電界電子放出特性を示す。この図から、低温（５５０℃）合成の試料においても、ターンオン電界１．３Ｖ／μｍ、閾値電界２．３Ｖ／μｍの優れた電子放出特性が得られることが判った。 Furthermore, the process temperature reduction considered to be necessary when using a glass substrate was examined. FIG. 12 shows the field electron emission characteristics of low-temperature synthetic patterned carbon nanotubes with a growth temperature of 550 ° C. and a diameter of 50 μm and a pitch of 100 μm. From this figure, it was found that excellent electron emission characteristics with a turn-on electric field of 1.3 V / μm and a threshold electric field of 2.3 V / μm can be obtained even in a low-temperature (550 ° C.) synthesized sample.
図１３にエミッション電流の安定性を示す。図より、エミッション電流が安定していることが判る。 FIG. 13 shows the stability of the emission current. From the figure, it can be seen that the emission current is stable.
なお、上記のカーボンナノチューブの長さ、アスペクト比、パターン化によるピッチ等は一例であり、これに限るものではない。 The length, aspect ratio, patterning pitch, and the like of the carbon nanotubes described above are merely examples, and the present invention is not limited thereto.
本発明は、低消費電力，高輝度光源への応用、大型低消費電力，高輝度薄型ディスプレイ（ＦＥＤ：Field Emission Display）として有用である。 INDUSTRIAL APPLICABILITY The present invention is useful as a low power consumption, application to a high luminance light source, a large size low power consumption, high luminance thin display (FED: Field Emission Display).
１０ カーボンナノチューブ群 10 Carbon nanotube group
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| JP2011210439A (en) * | 2010-03-29 | 2011-10-20 | Toppan Printing Co Ltd | Electron emission element, method of manufacturing the same, and surface light emitting element using the electron emission element |
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