JP2011154980A - Field emission type electron source and method of manufacturing the same - Google Patents
Field emission type electron source and method of manufacturing the same Download PDFInfo
- Publication number
- JP2011154980A JP2011154980A JP2010017440A JP2010017440A JP2011154980A JP 2011154980 A JP2011154980 A JP 2011154980A JP 2010017440 A JP2010017440 A JP 2010017440A JP 2010017440 A JP2010017440 A JP 2010017440A JP 2011154980 A JP2011154980 A JP 2011154980A
- Authority
- JP
- Japan
- Prior art keywords
- cold cathode
- field emission
- carbon material
- electron source
- emitter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Cold Cathode And The Manufacture (AREA)
Abstract
Description
本発明は、電界が印加されることにより電子を放出する電界放出型電子源とその製造方法に関する。 The present invention relates to a field emission electron source that emits electrons when an electric field is applied, and a method of manufacturing the same.
従来、電子顕微鏡、電子線管、Ｘ線管等に用いられる電界放出型電子源において、電界が印加されることにより電子を放出する冷陰極（エミッタ）を、グラファイト材に水素などのプラズマを照射してグラファイト材上にナノ構造体を形成した炭素材で形成することが知られている。その冷陰極を構成するグラファイト材料として、水素などのプラズマ処理を施すことにより作製されるナノメートルの針状構造を有するグラファイトナノクレータ（GRANC）がある。これは、カーボンナノチューブ等の炭素系電子放出材料に比べて、強電界領域での電子放出特性に優れていることが知られている。 Conventionally, in a field emission electron source used for an electron microscope, an electron beam tube, an X-ray tube, etc., a cold cathode (emitter) that emits electrons when an electric field is applied is irradiated, and a plasma such as hydrogen is irradiated on a graphite material. Thus, it is known to form a carbon material in which a nanostructure is formed on a graphite material. As a graphite material constituting the cold cathode, there is a graphite nanocrater (GRANC) having a nanometer needle-like structure manufactured by performing a plasma treatment such as hydrogen. This is known to be superior in electron emission characteristics in a strong electric field region as compared with carbon-based electron emission materials such as carbon nanotubes.
このGRANCが良好な電子放出特性を有する理由として、ナノメートルの針状構造への強力な電界集中があげられるが、これに用いられる炭素材は、重金属を含む炭素材でなければならない。加えて、高効率で良好な電界放出特性を得るためには、電界集中係数を高める必要があり、そのためにプラズマ照射前処理として、予め機械加工等によりマイクロメートル領域にまで炭素材自体の先鋭化を図ることが必要である。更に、電子放出に好適なナノ構造を実現するためには、上記の前処理で先鋭化した炭素材について水素プラズマ等を用いてエッチング処理を行う必要がある（特許文献１参照）。 The reason why this GRANC has a good electron emission characteristic is a strong electric field concentration on a nanometer needle-like structure, and the carbon material used for this must be a carbon material containing a heavy metal. In addition, in order to obtain high efficiency and good field emission characteristics, it is necessary to increase the electric field concentration factor. For this reason, as a pretreatment for plasma irradiation, the carbon material itself is sharpened to the micrometer range by machining or the like in advance. It is necessary to plan. Furthermore, in order to realize a nanostructure suitable for electron emission, the carbon material sharpened by the above pretreatment needs to be etched using hydrogen plasma or the like (see Patent Document 1).
上記のように、従来のGRANCを冷陰極として用いる電界型電子放出源では、プラズマエッチング前の前処理として、炭素基材の先端を機械加工等でマイクロメートル領域まで先鋭化することが必要であり、原材料の加工にコストがかかる。この先鋭化は、化学的加工によっても実現できるが、その後にプラズマ照射等によるエッチング処理が必要とされるため、その処理に必要な装置とその使用にコストがかかっていた。 As described above, in a field-type electron emission source using conventional GRANC as a cold cathode, it is necessary to sharpen the tip of the carbon substrate to the micrometer range by machining or the like as a pretreatment before plasma etching. Cost of processing raw materials. This sharpening can be realized by chemical processing, but since an etching process such as plasma irradiation is required after that, an apparatus necessary for the process and its use are costly.
また、プラズマ照射を行うには真空装置が必須であり、素材を真空チャンバに装填するといった操作を必要とするため、歩留まりが低い原因となっていた。 In addition, a vacuum apparatus is indispensable for performing plasma irradiation, and an operation of loading a material into a vacuum chamber is required, which causes a low yield.
本発明は、上記のような電界放出型電子源の製造に際し、冷陰極を構成する炭素材の表面に炭素のナノメートル構造（炭素シートが重なり合った構造）を形成することで炭素材の先鋭化を実現すると共に、その先鋭化を１回の工程で行うことで製造コストを抑えることができる製造方法と、この方法で製造された電界放出型電子源を提供することを目的とする。 The present invention sharpens the carbon material by forming a carbon nanometer structure (a structure in which carbon sheets overlap) on the surface of the carbon material constituting the cold cathode in the manufacture of the field emission electron source as described above. It is an object of the present invention to provide a manufacturing method capable of suppressing the manufacturing cost by performing sharpening in one step and a field emission electron source manufactured by this method.
本発明は、電界が印加されることにより電子を放出する冷陰極を備えた電界放出型電子源の製造方法であって、前記冷陰極の素材となる炭素材を水素酸素混合ガスの燃焼炎に暴露することで、該炭素材の表面に炭素のナノメートル構造を形成するエッチング処理を行い、得られた炭素材で前記冷陰極を形成することを特徴とする。 The present invention relates to a method of manufacturing a field emission electron source including a cold cathode that emits electrons when an electric field is applied, wherein a carbon material that is a material of the cold cathode is used as a combustion flame of a hydrogen-oxygen mixed gas. By performing the exposure, an etching process for forming a nanometer structure of carbon on the surface of the carbon material is performed, and the cold cathode is formed of the obtained carbon material.
本発明の方法によれば、炭素材を水素酸素混合ガスの燃焼炎に暴露するという１回の工程（エッチング処理）で、該炭素材のマイクロメートル領域に至る先端の先鋭化と同時に、先鋭化された先端の表面に炭素のナノメートル構造が形成される。そして、この炭素材で電界放出型電子源の冷陰極を形成する。従って、従来の真空中でのプラズマ照射のように手間とコストがかかる工程が不要であり、歩留まりが良く低コストで、優れた電界放出特性を有する電界放出型電子源が得られる。 According to the method of the present invention, the carbon material is exposed to a combustion flame of a hydrogen-oxygen mixed gas in one step (etching process), and at the same time as the tip of the carbon material reaching the micrometer region is sharpened. A carbon nanometer structure is formed on the surface of the tip. And the cold cathode of a field emission type electron source is formed with this carbon material. Therefore, a process that requires labor and cost like conventional plasma irradiation in a vacuum is not required, and a field emission electron source having excellent field emission characteristics can be obtained with good yield and low cost.
本発明のもう１つの態様は、電界が印加されることにより電子を放出する冷陰極を備えた電界放出型電子源であって、前記冷陰極の素材となる炭素材を水素酸素混合ガスの燃焼炎に暴露することで、該炭素材の表面に炭素のナノメートル構造を形成するエッチング処理を行い、得られた炭素材で前記冷陰極を形成したことを特徴とする。 Another aspect of the present invention is a field emission electron source including a cold cathode that emits electrons when an electric field is applied, and a carbon material that is a material of the cold cathode is burned with a hydrogen-oxygen mixed gas. The cold cathode is formed of the carbon material obtained by performing an etching process for forming a carbon nanometer structure on the surface of the carbon material by exposure to a flame.
本発明の電界放出型電子源では、冷陰極を構成する炭素材の先端をマイクロメートルの領域まで先鋭化すると同時に、その先鋭化された先端部の表面に数ナノメートル程度のナノ構造を形成することができるので、その製造工程を１回とすることができて製造コストを抑えることが可能となる。 In the field emission electron source of the present invention, the tip of the carbon material constituting the cold cathode is sharpened to the micrometer region, and at the same time, a nanostructure of about several nanometers is formed on the surface of the sharpened tip. Therefore, the manufacturing process can be performed once, and the manufacturing cost can be suppressed.
本発明の電界放出型電子源において、前記冷陰極から放出された電子が向かうターゲットと該冷陰極との間で前記冷陰極の周囲に制御電極が配置され、前記ターゲットと前記制御電極との間に、前記ターゲットと前記冷陰極との間に印加するのと同じ電圧が印加されることが好ましい。 In the field emission electron source of the present invention, a control electrode is disposed around the cold cathode between the cold cathode and a target to which electrons emitted from the cold cathode travel, and between the target and the control electrode. Further, it is preferable that the same voltage as that applied between the target and the cold cathode is applied.
この構成によれば、制御電極が、ターゲットと冷陰極との間の距離よりもターゲットと制御電極との間の距離が短くなるように配置されるので、エミッタよりもそれを囲む制御電極の電界強度が強く、Ｘ線発生ターゲットで発生したイオンは、冷陰極に向かうより制御電極に向かっていく。このため、冷陰極の先端部におけるイオン衝撃頻度は従来の電界放出型電子源に比して圧倒的に小さくなり、該イオンによる冷陰極先端部の破壊を抑制することができる。 According to this configuration, since the control electrode is arranged such that the distance between the target and the control electrode is shorter than the distance between the target and the cold cathode, the electric field of the control electrode that surrounds the control electrode rather than the emitter. The intensity is high and ions generated at the X-ray generation target are directed toward the control electrode rather than toward the cold cathode. For this reason, the ion bombardment frequency at the tip of the cold cathode is overwhelmingly lower than that of a conventional field emission electron source, and the destruction of the tip of the cold cathode due to the ions can be suppressed.
以下、本発明による電界放出型電子源の製造方法について説明する。 Hereinafter, a method for manufacturing a field emission electron source according to the present invention will be described.
まず、電界放出型電子源の冷陰極（エミッタ）を形成する炭素材は、炭素を含有する材料であればよく、その形状は棒状（ロッド型）又は板状でよい。この炭素材を水素及び酸素の燃焼炎（トーチ）に暴露して600度Ｃ以上の高温に加熱することにより、上記燃焼炎中の水蒸気、残留酸素及び水素による炭素材のエッチング効果を利用して炭素材の先鋭化を達成することができる。 First, the carbon material forming the cold cathode (emitter) of the field emission electron source may be a material containing carbon, and the shape thereof may be a rod shape (rod shape) or a plate shape. By exposing this carbon material to a combustion flame (torch) of hydrogen and oxygen and heating it to a high temperature of 600 ° C. or higher, the etching effect of the carbon material by water vapor, residual oxygen and hydrogen in the combustion flame is utilized. Sharpening of the carbon material can be achieved.
具体的には、図１に示すように、棒状又は板状の炭素材１０を水素酸素混合ガス（モル比で水素：酸素＝ 4.5：1程度）の燃焼炎１１内（高温加熱域）に暴露する。炭素材１０が2000°Ｃ以上に加熱されると、炭素材中の炭素が酸化及び水素化などにより、エッチングされる。 Specifically, as shown in FIG. 1, a rod-like or plate-like carbon material 10 is exposed in a combustion flame 11 (high temperature heating region) of a hydrogen-oxygen mixed gas (hydrogen: oxygen = 4.5: 1 in molar ratio). To do. When the carbon material 10 is heated to 2000 ° C. or more, the carbon in the carbon material is etched by oxidation and hydrogenation.
この工程によれば、炭素材の水素酸素燃焼炎への暴露は大気圧中で実施できるので、簡便な設備で炭素材のマイクロメートル領域に至る先端の先鋭化とナノ構造の作製を実現できる。この先鋭化は、上記の燃焼炎による高温状態下で行うことにより、効率が高く機械加工による先鋭化に匹敵するものとなる。 According to this process, since the carbon material can be exposed to the hydrogen-oxygen combustion flame at atmospheric pressure, the sharpening of the tip of the carbon material to the micrometer region and the production of the nanostructure can be realized with simple equipment. This sharpening is performed at a high temperature by the combustion flame described above, so that the efficiency is high and comparable to the sharpening by machining.
このとき、水素燃焼炎によるエッチングの効果は、凡そ600度Ｃ（約900度Ｋ）以上では急激に失われるため、水素燃焼炎を用いることでは、上記のように機械加工に匹敵する炭素材の先鋭化を行うことができない。しかしながら、水素燃焼炎に酸素を加えて徐々に燃焼温度を上げていくと、燃焼炎中の主な分子種はＨ２Ｏとなり、この新たに生成されたＨ２Ｏは、約900度Ｋ以上では、炭素材料をエッチングする効果を有するようになる。更に2300度Ｋ以上では、非常に高い反応性を示すようになる。 At this time, the etching effect by the hydrogen combustion flame is rapidly lost at about 600 degrees C (about 900 degrees K) or more. Therefore, by using the hydrogen combustion flame, the carbon material comparable to machining as described above can be obtained. Sharpening cannot be performed. However, when oxygen is added to the hydrogen combustion flame and the combustion temperature is gradually raised, the main molecular species in the combustion flame becomes H 2 O, and this newly generated H 2 O is about 900 degrees K or more. Then, it comes to have an effect which etches a carbon material. Furthermore, at 2300 degrees K or more, it will show very high reactivity.
上記のように炭素材が水素酸素燃焼炎に暴露されることにより、炭素材に含まれる炭素原子は、与えられた熱で分解及び再構成され、後述の図３（Ｂ）に示すように、数〜数十ナノメートル程度の炭素シートが炭素材の長尺方向に束ねられた構造を形成するようになる
このような炭素シートを備えた炭素材で冷陰極（エミッタ）を形成した電界放出型電子源において、冷陰極に強い電界が印加されると、電界放出により炭素シートの端部から電子が放出される。その電子放出による単位径あたりの電流は、GRANCよりも大きい。従って、上記の炭素シート構造は、大電流が要求される真空デバイス（Ｘ線管、電界放出ランプなど）に好適な炭素系電界放出材料となり得る。
When the carbon material is exposed to the hydrogen-oxygen combustion flame as described above, the carbon atoms contained in the carbon material are decomposed and reconfigured by the applied heat, as shown in FIG. A field emission type in which a cold cathode (emitter) is formed of a carbon material having such a carbon sheet, in which carbon sheets of several to several tens of nanometers are bundled in the longitudinal direction of the carbon material. When a strong electric field is applied to the cold cathode in the electron source, electrons are emitted from the edge of the carbon sheet by field emission. The current per unit diameter due to the electron emission is larger than that of GRANC. Therefore, the above carbon sheet structure can be a carbon-based field emission material suitable for vacuum devices (such as X-ray tubes and field emission lamps) that require a large current.
また、一般的に、カーボンナノチューブ等の炭素系ナノ材料の作製には、重金属からなる触媒を用いなければならないが、本発明によれば、電子放出源に好適なナノ構造を作製するために触媒を用いる必要がない。従って、この点からも、製造コストを削減できる。 In general, a carbon-based nanomaterial such as a carbon nanotube must be prepared using a catalyst made of heavy metal. According to the present invention, a catalyst for producing a nanostructure suitable for an electron emission source is used. Need not be used. Therefore, also from this point, the manufacturing cost can be reduced.
図２（Ａ）及び（Ｂ）は、エッチング前及びエッチング後の炭素材の走査型電子顕微鏡（ＳＥＭ）写真である。エッチングが施された時間は10秒である。この例では、グラファイト粒子を有機物系接着剤で固めたものを無酸素雰囲気化で炭化した炭素材を利用した。作製した炭素材中に重金属類は確認されなかった。写真から機械加工を施すことなく先端が先鋭化されていることが確認できる。 2A and 2B are scanning electron microscope (SEM) photographs of the carbon material before and after etching. The etching time is 10 seconds. In this example, a carbon material obtained by carbonizing graphite particles hardened with an organic adhesive in an oxygen-free atmosphere was used. Heavy metals were not confirmed in the produced carbon material. It can be confirmed from the photograph that the tip is sharpened without machining.
図３（Ａ）及び（Ｂ）は、エッチング前後の炭素材の拡大写真である。図３（Ａ）に示すエッチング前の状態では、炭素材を構成するグラファイトがランダムに配列していることを確認できる。一方、図３（Ｂ）に示すように、エッチングが施された炭素材表面には、数ナノメートル程度の炭素シートが長尺方向に向かって配向している。これは、高温エッチングに伴って、炭素材中の炭素原子が高温処理により炭素シートを形成したことによると考えられる。 3A and 3B are enlarged photographs of the carbon material before and after etching. In the state before etching shown in FIG. 3A, it can be confirmed that the graphite constituting the carbon material is randomly arranged. On the other hand, as shown in FIG. 3B, on the etched carbon material surface, a carbon sheet of about several nanometers is oriented in the longitudinal direction. This is considered to be due to the fact that carbon atoms in the carbon material formed a carbon sheet by high-temperature treatment with high-temperature etching.
次に、本発明の方法で製造される電界放出型電子源の使用例として、電界放出型Ｘ線管について説明する。これは、上記炭素材のような電界放出型電子材料からなる冷陰極（エミッタ）に強電界を印加して電子を放出させ、電子をＸ線発生ターゲットに照射することによってＸ線を発生させるものである。かかるＸ線管において、エミッタから電子を放出させるためには、Ｘ線発生ターゲットとエミッタとの間に高電圧を印加し、エミッタ先端から電子放出をさせるのに十分な電界強度を与えなければならない。 Next, a field emission X-ray tube will be described as an example of use of the field emission electron source manufactured by the method of the present invention. This is a technique in which a strong electric field is applied to a cold cathode (emitter) made of a field emission electronic material such as the carbon material to emit electrons, and X-rays are generated by irradiating the X-ray generation target with electrons. It is. In such an X-ray tube, in order to emit electrons from the emitter, a high voltage must be applied between the X-ray generation target and the emitter to give a sufficient electric field strength to emit electrons from the tip of the emitter. .
このタイプのＸ線管は、図４に模式的に示すように、電界放出型電子源を構成するエミッタ１とＸ線ターゲット３と制御電極４とをガラス管内に封入し、その内部を高真空状態に保持するように構成される。このＸ線ターゲット３とエミッタ１との間に電圧源２から高電圧ＶＥＴを印加すると共に、エミッタ１の先端に強電界を印加することにより、エミッタ１から放出された電子がターゲット３に照射され、ターゲット３からＸ線が発生する。 In this type of X-ray tube, as schematically shown in FIG. 4, an emitter 1, an X-ray target 3 and a control electrode 4 constituting a field emission electron source are enclosed in a glass tube, and the inside thereof is subjected to a high vacuum. Configured to hold in a state. A high voltage VET is applied from the voltage source 2 between the X-ray target 3 and the emitter 1, and a strong electric field is applied to the tip of the emitter 1 to irradiate the target 3 with electrons emitted from the emitter 1. Then, X-rays are generated from the target 3.
図４に示したＸ線管に用いられている電界放出型電子源は、前述のように作製した炭素材１０からなる棒状の冷陰極（エミッタ）１の上方に、制御電極４として円筒状の導電性材料をエミッタ１と心合せして配置した構造である。すなわち、エミッタ１は、制御電極４の中心の下方位置に配置されている。そして、制御電極４は、ターゲット３とエミッタ１との間の距離よりもターゲット３と当該制御電極４との間の距離が短くなるように配置されている。 The field emission electron source used in the X-ray tube shown in FIG. 4 has a cylindrical shape as the control electrode 4 above the rod-like cold cathode (emitter) 1 made of the carbon material 10 produced as described above. In this structure, a conductive material is aligned with the emitter 1. That is, the emitter 1 is disposed at a position below the center of the control electrode 4. The control electrode 4 is disposed such that the distance between the target 3 and the control electrode 4 is shorter than the distance between the target 3 and the emitter 1.
この構造によれば、電界が図の矢印方向に印加されると、制御電極４の電界強度はエミッタ１のそれよりも強くなる。すなわち、この電界放出型電子源においては、エミッタ１を制御電極４で取り囲み、制御電極４は、これに印加される電界強度がエミッタ１よりも強くなるように配置される。 According to this structure, when an electric field is applied in the direction of the arrow in the figure, the electric field strength of the control electrode 4 becomes stronger than that of the emitter 1. That is, in this field emission type electron source, the emitter 1 is surrounded by the control electrode 4, and the control electrode 4 is arranged so that the electric field strength applied thereto is stronger than that of the emitter 1.
ここで、エミッタ１と制御電極４が同電位の状態でエミッタ‐ターゲット間に高電圧ＶＥＴを印加すると、図５に示すように、電気力線がエミッタ１の先端部へ集中するのが緩和される。そして、より高い電界強度が印加された制御電極４へイオンが流れるため、エミッタ１へのイオン流入量が少なくなる。 Here, when the high voltage VET is applied between the emitter and target while the emitter 1 and the control electrode 4 are at the same potential, the concentration of the electric lines of force on the tip of the emitter 1 is reduced as shown in FIG. Is done. Since ions flow to the control electrode 4 to which a higher electric field strength is applied, the amount of ions flowing into the emitter 1 is reduced.
なお、電気力線の数は、ターゲット・エミッタ間の距離、印加電圧、エミッタ１と制御電極４の幾何学的位置関係等によって変動する。 Note that the number of lines of electric force varies depending on the distance between the target and the emitter, the applied voltage, the geometric positional relationship between the emitter 1 and the control electrode 4, and the like.
上記電界放出型電子源では、エミッタ１を囲む制御電極４は、エミッタ１に比べて仕事関数φの高い材料で構成することが好ましい。これにより、エミッタ１からの電子放出よりも制御電極４からの電子放出が優勢となる可能性をなくすことができる。 In the field emission electron source, the control electrode 4 surrounding the emitter 1 is preferably made of a material having a work function φ higher than that of the emitter 1. Thereby, the possibility that the electron emission from the control electrode 4 becomes dominant over the electron emission from the emitter 1 can be eliminated.
また、制御電極４は、イオン衝突によるスパッタを生じない材料が好適であり、原子番号の大きい材料或いは共有結合性の強い材料が好ましい。なぜなら、イオンは数１０ｋｅＶのエネルギーを有しているため、スパッタにより更なるイオンの発生が起こり得るからである。 The control electrode 4 is preferably made of a material that does not cause sputtering due to ion collision, and is preferably made of a material having a large atomic number or a material having strong covalent bonding. This is because ions have energy of several tens of keV, so that further ions can be generated by sputtering.
本発明の電界放出型電子源は、図４の構成に限らず、図６に示すように、エミッタ１の上方周囲に針状の制御電極４を複数配置した構造でもよい。この場合、エミッタ１は、その上方円周上に配置した制御電極４からなる円の中心位置に配置されている。そして、制御電極４は、ターゲット３とエミッタ１との間の距離よりもターゲット３と当該制御電極４との間の距離が短くなるように配置されている。 The field emission electron source of the present invention is not limited to the configuration of FIG. 4, and may have a structure in which a plurality of needle-like control electrodes 4 are arranged around the emitter 1 as shown in FIG. 6. In this case, the emitter 1 is arranged at the center position of a circle composed of the control electrodes 4 arranged on the upper circumference thereof. The control electrode 4 is disposed such that the distance between the target 3 and the control electrode 4 is shorter than the distance between the target 3 and the emitter 1.
従って、この構造の電界放出型電子源においても、電界が図の矢印方向に印加されると、制御電極４の電界強度はエミッタ１のそれよりも強くなる。このため、より高い電界強度を印加された制御電極４へイオンが流れるので、エミッタ１へのイオン流入量が少なくなり、エミッタ１における電子放出部のスパッタによる破壊が抑えられる。 Therefore, also in the field emission electron source having this structure, when the electric field is applied in the direction of the arrow in the figure, the electric field intensity of the control electrode 4 becomes stronger than that of the emitter 1. For this reason, since ions flow to the control electrode 4 to which a higher electric field strength is applied, the amount of ions flowing into the emitter 1 is reduced, and destruction of the electron emission portion in the emitter 1 due to sputtering is suppressed.
以上のように、図４及び図６の電界放出型電子源においては、エミッタ１を制御電極４で取り囲み、制御電極４は、ターゲット３とエミッタ１との間の距離よりもターゲット３と制御電極４との間の距離が短くなるように配置されることで、制御電極４に印加される電界強度がエミッタ１に印加される電界よりも強くなる。このため、Ｘ線発生ターゲットで発生したイオンは、エミッタ１に向かうよりも多く制御電極４に向かうので、エミッタ１の先端部におけるイオン衝撃頻度は従来の電界放出型Ｘ線管に比して圧倒的に小さくなる。これにより、実用に供し得る寿命を有する電界放出型Ｘ線管が得られる。 As described above, in the field emission electron source of FIGS. 4 and 6, the emitter 1 is surrounded by the control electrode 4, and the control electrode 4 has a larger distance than the target 3 and the control electrode 4 than the distance between the target 3 and the emitter 1. The electric field strength applied to the control electrode 4 is stronger than the electric field applied to the emitter 1 by being arranged so that the distance to the electrode 4 is short. For this reason, ions generated at the X-ray generation target are directed to the control electrode 4 more than toward the emitter 1, so that the ion bombardment frequency at the tip of the emitter 1 is overwhelming as compared with the conventional field emission X-ray tube. Become smaller. Thereby, a field emission X-ray tube having a useful life can be obtained.
また、別の実施形態として、図４又は図６の電界放出型電子源において、エミッタへのイオン衝突の頻度に応じて、制御電極へのイオンの引き込み量を調節可能とする。図７は、その構成例を示す。 As another embodiment, in the field emission electron source of FIG. 4 or 6, the amount of ions drawn into the control electrode can be adjusted according to the frequency of ion collision with the emitter. FIG. 7 shows an example of the configuration.
これは、前述のようにエミッタ１と制御電極４を同電位とする構成においても、エミッタ１へのイオン衝突が問題となる場合に対処するものである。具体的には、例えば図４の電界放出型電子源において、エミッタ１と制御電極４との間に、図７に示すようにエミッタ１と制御電極４の間に電位差を設ける調節用可変電源６が接続される。 This is to deal with the case where ion collision with the emitter 1 becomes a problem even in the configuration in which the emitter 1 and the control electrode 4 are set to the same potential as described above. More specifically, for example, in the field emission electron source of FIG. 4, an adjusting variable power source 6 that provides a potential difference between the emitter 1 and the control electrode 4 and between the emitter 1 and the control electrode 4 as shown in FIG. Is connected.
この電源６は、前述した制御電極４に印加される電界強度がエミッタ１に印加される電界強度よりも強いという電界強度の関係が反転しない（すなわち、エミッタ１に印加される電界強度が、制御電極４に印加される電界強度よりも強くならない）範囲で、電圧を印加するように調節される。こうして制御電極４の電位をエミッタ１の電位より低くする程度を調整することで、制御電極４へのイオンの引き込み量を調整することができ、ひいてはエミッタへのイオンの衝突を更に減少又は微調整することができる。 This power supply 6 does not reverse the relationship of the electric field strength that the electric field strength applied to the control electrode 4 is stronger than the electric field strength applied to the emitter 1 (that is, the electric field strength applied to the emitter 1 is controlled). The voltage is adjusted to be applied within a range that does not become stronger than the electric field strength applied to the electrode 4. In this way, by adjusting the degree to which the potential of the control electrode 4 is lower than the potential of the emitter 1, the amount of ions attracted to the control electrode 4 can be adjusted, thereby further reducing or finely adjusting the collision of ions with the emitter. can do.
上記のようにして作製されたエッチング済み炭素材で冷陰極（エミッタ）を形成したＸ線管（図４）を製作し、その電界放出特性を評価した。このＸ線管の制御電極４の材料にはＴｉ、Ｘ線発生ターゲット３にはＢｅ窓にＣｕを堆積したものを用いた。また、制御電極４に対して、エミッタ１は１ｍｍ程度下方に位置するようにした。これは、制御電極４部分の電界強度をエミッタ１の先端よりも強くすることにより、Ｘ線発生ターゲット３から生じるイオンによるエミッタ１の先端部の破壊を抑制するためである。 An X-ray tube (FIG. 4) having a cold cathode (emitter) formed of an etched carbon material produced as described above was manufactured, and its field emission characteristics were evaluated. Ti was used as the material of the control electrode 4 of the X-ray tube, and the X-ray generation target 3 was made of Cu deposited on the Be window. Further, the emitter 1 is positioned about 1 mm below the control electrode 4. This is because the breakdown of the tip of the emitter 1 due to ions generated from the X-ray generation target 3 is suppressed by making the electric field strength of the control electrode 4 portion stronger than the tip of the emitter 1.
このＸ線管内部の真空度は、ゲッター材等を用いて10−７ Pa以下の高真空状態とした。エミッタへのイオン衝撃頻度は真空度に比例するので、できるだけ高真空にすることが必要である。 The degree of vacuum inside the X-ray tube was set to a high vacuum state of 10 −7 Pa or less using a getter material or the like. Since the frequency of ion bombardment on the emitter is proportional to the degree of vacuum, it is necessary to make the vacuum as high as possible.
図８は、上記Ｘ線管の電流−電圧特性を示している。この特性から、Ｘ線発生ターゲットに電圧を印加すると、閾値電圧４ｋＶで電子放出が確認され、８ｋＶ以上の印加電圧で１ｍＡを超える電界放出電流が得られることがわかる。本実施例においては、３ｍＡの直流駆動も可能であることを確認しており、本発明の方法で作製された炭素材からなるエミッタは優れた電界放出特性を有することが明らかとなった。 FIG. 8 shows the current-voltage characteristics of the X-ray tube. From this characteristic, it can be seen that when a voltage is applied to the X-ray generation target, electron emission is confirmed at a threshold voltage of 4 kV, and a field emission current exceeding 1 mA is obtained at an applied voltage of 8 kV or higher. In this example, it was confirmed that a DC drive of 3 mA was possible, and it became clear that the emitter made of the carbon material produced by the method of the present invention has excellent field emission characteristics.
以上のように、本発明によれば、従来の製造方法に比して遥かに簡便に且つ低コストで、良好な電子放出特性を有する電界放出型電子源を提供することができる。 As described above, according to the present invention, it is possible to provide a field emission type electron source having good electron emission characteristics, which is much simpler and lower in cost than the conventional manufacturing method.
上記実施形態では、電界放出型電子源をＸ線管に用いた場合について説明したが、本発明によって得られる電界放出型電子源は、Ｘ線管のほか、電界放出電子源を利用する全ての装置、例えば電子線管の電子線源部、走査型電子顕微鏡及び透過型電子顕微鏡の電子源部、電子線励起型蛍光灯の電子源部、電子線マイクロプローブアナライザの電子線源部、カソードルミネッセンス装置の電子線源部等に、好適に用いられる。 In the above embodiment, the case where the field emission electron source is used in the X-ray tube has been described. Apparatus, for example, electron beam source part of electron tube, electron source part of scanning electron microscope and transmission electron microscope, electron source part of electron beam excitation type fluorescent lamp, electron beam source part of electron beam microprobe analyzer, cathode luminescence It is suitably used for an electron beam source part of the apparatus.
１・・・エミッタ、２…電圧源、３…ターゲット、４・・・制御電極、５…孔、６…調節電源、１０…炭素材、１１…水素酸素燃焼炎。 DESCRIPTION OF SYMBOLS 1 ... Emitter, 2 ... Voltage source, 3 ... Target, 4 ... Control electrode, 5 ... Hole, 6 ... Control power supply, 10 ... Carbon material, 11 ... Hydrogen oxygen combustion flame.
Claims (3)
3. The field emission electron source according to claim 2, wherein a control electrode is disposed around the cold cathode between the cold cathode and a target to which electrons emitted from the cold cathode travel, and the target and the control are arranged. A field emission electron source, wherein the same voltage as that applied between the target and the cold cathode is applied between electrodes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2010017440A JP5406748B2 (en) | 2010-01-28 | 2010-01-28 | Field emission electron source and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2010017440A JP5406748B2 (en) | 2010-01-28 | 2010-01-28 | Field emission electron source and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2011154980A true JP2011154980A (en) | 2011-08-11 |
| JP5406748B2 JP5406748B2 (en) | 2014-02-05 |
Family
ID=44540787
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2010017440A Expired - Fee Related JP5406748B2 (en) | 2010-01-28 | 2010-01-28 | Field emission electron source and manufacturing method thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP5406748B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014007098A1 (en) * | 2012-07-02 | 2014-01-09 | スタンレー電気株式会社 | Deep ultraviolet laser light source by means of electron beam excitation |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001348296A (en) * | 2000-04-05 | 2001-12-18 | Kobe Steel Ltd | Diamond having needle-shaped surface, carbon-based material having cilium-like surface, method of producing these materials and electrode and electronic device using these materials |
| JP2005032638A (en) * | 2003-07-09 | 2005-02-03 | Stanley Electric Co Ltd | Manufacturing method of cold cathode, and device using cold cathode |
| JP2010218894A (en) * | 2009-03-17 | 2010-09-30 | Jeol Ltd | Emitter tip acumination method and device of field ionization type gas ion source |
-
2010
- 2010-01-28 JP JP2010017440A patent/JP5406748B2/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001348296A (en) * | 2000-04-05 | 2001-12-18 | Kobe Steel Ltd | Diamond having needle-shaped surface, carbon-based material having cilium-like surface, method of producing these materials and electrode and electronic device using these materials |
| JP2005032638A (en) * | 2003-07-09 | 2005-02-03 | Stanley Electric Co Ltd | Manufacturing method of cold cathode, and device using cold cathode |
| JP2010218894A (en) * | 2009-03-17 | 2010-09-30 | Jeol Ltd | Emitter tip acumination method and device of field ionization type gas ion source |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014007098A1 (en) * | 2012-07-02 | 2014-01-09 | スタンレー電気株式会社 | Deep ultraviolet laser light source by means of electron beam excitation |
| JP2014011377A (en) * | 2012-07-02 | 2014-01-20 | Stanley Electric Co Ltd | Deep ultraviolet laser light source |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5406748B2 (en) | 2014-02-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Parmee et al. | X-ray generation using carbon nanotubes | |
| JP4783239B2 (en) | Electron emitter material and electron emission application device | |
| Terranova et al. | Nanodiamonds for field emission: state of the art | |
| KR102368515B1 (en) | An electron emitter for an x-ray tube | |
| US20020006489A1 (en) | Electron emitter, manufacturing method thereof and electron beam device | |
| JP2001180920A (en) | Method of machining nano tube and method of producing field emission-type cold cathode and indicator | |
| Zhao et al. | Field emission from screen-printed carbon nanotubes irradiated by tunable ultraviolet laser in different atmospheres | |
| CN1538485A (en) | Manufacturing method of electron emission source | |
| JP5406748B2 (en) | Field emission electron source and manufacturing method thereof | |
| JP4872042B2 (en) | High-density carbon nanotube aggregate and method for producing the same | |
| Koh et al. | Low temperature direct of graphene onto metal nano‐spindt tip with applications in electron emission | |
| JP4955265B2 (en) | Method and apparatus for manufacturing semiconductor device | |
| Chen et al. | Analysis of a laser post-process on a buckypaper field emitter for high and uniform electron emission | |
| Hu et al. | A novel cold cathode design for S-band continuous-wave magnetron | |
| CN108987215B (en) | Method for improving field emission performance of graphene sheet-carbon nanotube array composite material | |
| KR102362517B1 (en) | Tungsten doped grapheneoxide, manufacturing method thereof and electron emitter including the same | |
| JP4863590B2 (en) | Carbon nanotube modification method, carbon nanotube and electron emission source | |
| JP2006049293A (en) | Field-emission electron gun and electron beam application apparatus using the same | |
| JP2004146158A (en) | Field emission type x-ray source | |
| KR101121639B1 (en) | Cathode structure of electron emitting device | |
| JP2004335420A (en) | Fe type x-ray radiography system and method of manufacturing fe emitter used in the same | |
| JP2002022899A (en) | Electron beam irradiator | |
| JP5081851B2 (en) | Manufacturing method of field emission electron source | |
| JP2007095580A (en) | Field emitter using carbon nanotube | |
| JP2008044828A (en) | Carbon nanotube forming device and carbon nanotube forming method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20130108 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20130920 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20131008 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20131101 |
|
| LAPS | Cancellation because of no payment of annual fees |