200828399 •九、發明說明： 【發明所屬之技術領域】 本發明涉及-種場發射陰極的製備方法，尤其涉及— 種基於奈米碳管的場發射陰極的製備方法。八 【先前技術】 奈米石反官係-種新型碳材料，其具有極其優異的導電 性月b，且其具有幾乎接近理論極限的尖端表 賴小，其局部電場越集中），故，奈米碳管=== 場發射材料’其具有極低場發射電壓，可傳輸極大電流密 度’且電流極穩定’因而非常適合做場發射顯示器的 組件。 x 用於發射元件的奈米碳管，一般為採用電弧放電法或 化學氣相沈積法(CVD法）生長的奈来碳管。將奈米碳管應 用於場發射顯示器的方式有··將含有奈米碳管的導電漿料 或者有機粘接劑印刷成圖形通過後續處理使得奈米碳管能 ^ 夠從漿料的埋藏中露出頭來成發射體。在此方法中，將含 有奈米碳管的導電漿料以厚膜鋼板印刷的方式塗布在導電 基板上，奈米碳管在漿料中發生彎曲，相互交織，不易开< 成垂直於導電基板的奈米碳管，為形成性能良好的發射尖 端，需對奈米碳管陣列進行後續處理，即將一層漿料剥離， 從而使奈米碳管從漿料的埋藏中露出頭來而成為發射體， 惟，剝離此漿料層對奈米碳管損傷很大。 另，上述方法製備的奈米碳管層中，奈米碳管基本上 队在導電基板上’相對導電基板垂直的奈米碳管較少。然 6 200828399 ’而’奈米碳管作為場發射體，係從奈米碳管的-端沿軸向 _ ^射出電子，故，奈米碳管趴在導電基板上不利於奈米碳 管場發射性能的發揮。 、」繁於此’確有必要提供—種可喊服上述缺點的奈 米碳管場發射陰極的製備方法，其不損傷奈米碳管，使奈 米碳管場發射體相對導電基板基本垂直，從而確保奈米碳 管場發射性能發揮良好。 【發明内容】 一種場發射陰極的製備方法，其包括以下步驟： &供一基底；在上述基底表面形成一導電薄膜層；在 導電薄膜層上形成一含碳的催化劑層；通入碳源氣與 載氣的混合氣體流經上述催化劑層表面；以及以雷射 光束聚焦照射基底從而生長奈米碳管陣列，形成場發 射陰極。 相較於先前技術，所述的場發射陰極的製備方法 、 中採用含碳的催化劑層用於雷射輔助化學氣相沈積 生長奈米碳管陣列。該催化劑層可有效吸收雷射能量 並加熱催化劑，可削弱雷射場強度，可在一定程度上 避免雷射破壞新生長出來的奈米碳管；同時，由該場 發射陰極的製備方法得到的場發射陰極中的奈米碳 管陣列垂直於基底，因此具有良好的場發射性能。 【實施方式】 以下將結合附圖對本發明作進一步的詳細說明。 請參閱圖1，本發明實施例場發射陰極的製傷方法 7 200828399 • 主要包括以下幾個步驟： • 步驟一：提供一基底。 本實施例中基底材料選用耐南溫材料製成。根據 不同應用，本實施例中基底材料還可分別選用透明或 不透明材料，如，當應用於半導體電子器件時可選擇 為矽、二氧化矽或金屬材料等不透明材料；當應用於 大面積平板顯示器時，優選為玻璃、可塑性有機材料 等透明材料。 步驟二：在上述基底表面形成一導電薄膜。 該導電薄膜可通過熱沈積、電子束沈積或藏射法 形成在上述基底表面。本實施例中，該導電薄膜材料 優選為氧化銦錫薄膜，其厚度為10〜100奈米，優選 為30奈米。 步驟三：在上述導電薄膜上形成一含碳的催化劑 層。 本實施例中，該含碳的催化劑層的製備方法包括 以下步驟：提供一種分散劑與一種含碳物質的混合 物，並與一溶劑混合形成溶液；將該溶液進行超聲波 分散處理；在該分散後的溶液中加入金屬硝酸鹽混合 物溶解得到一催化劑溶液；將該催化劑溶液均勻塗敷 於上述導電薄膜上；烘烤從而形成一含碳的催化劑 層。 其中，該含碳物質包括碳黑或石墨等含碳材料。 該分散劑用於將含碳物質均勻分散，優選為十二烷基 8 200828399 苯石黃酸鈉（Sodium Dodecyl Benzene Sulfonate, SDBS)。溶劑可選擇為乙醇溶液或水。該分散劑與含 碳物質的品質比為1:2〜1:10,本實施例優選為將 0〜100毫克的十二烷基苯磺酸鈉與100〜500毫克的碳 黑混合物與乙醇溶液混合形成溶液。 該金屬瑞酸鹽化合物包括确酸鎮（Mg(N〇3)2 · 6H2O) 與石肖酸鐵（Fe(N〇3)3.9H2〇)、石肖酸姑（Co(N〇3)2,6H2〇)或 石肖酸鎳（Ni (Ν〇3)2 · 6H2O)中任一種或幾種組成的混合 物。本實施例優選為將硝酸鐵（Fe(N〇3)r9H2〇)與硝酸 鎂（Mg(N〇3)2*6H2〇)加入到溶液中形成催化劑溶液，該 催化劑溶液中含有0. 01〜0. 5摩爾（Mol/L)的石肖酸鎮與 0. 01〜0. 5Mol/L的墙酸鐵。 烘烤的溫度為60〜100°C。烘烤的作用為將催化劑 溶液中的溶劑蒸發從而形成一含碳催化劑層。 本實施例中，該含碳的催化劑層的厚度為10〜100 微米。催化劑溶液塗敷於基底表面可採用旋轉塗敷的 方式，其轉速為1000〜5000轉/分鐘（rpm)，優選為 1500rpm 〇 步驟四：通入碳源氣與載氣的混合氣體流經上述 催化劑層表面。 該碳源氣優選為廉價氣體乙炔，也可選用其他碳 氫化合物如曱烷、乙烷、乙烯等。載氣氣體優選為氬 氣，也可選用其他惰性氣體如氮氣等。本實施例中， 碳源氣與載氣可通過一氣體喷嘴直接通入到上述催 9 200828399 • 化劑層表面附近。载氣與破源氣的通氣流量比例為 5 : 1〜ίο ·· 1，本實施例優選為通以200標準毫升/分 (seem)的氬氣與25sccm的乙炔。 步驟四：以雷射光束聚焦照射加熱催化劑層從而 生長奈米碳管陣列，得到場發射陰極。 本實施例中，雷射光束可通過傳統的氬離子雷射 器或二氧化碳雷射器產生，其功率為〇〜5瓦（W)，優 選為470mW。產生的雷射光束可通過一透鏡聚焦後從 正面直接照射在上述催化劑層表面，可以理解，該雷 射光束可採用垂直照射或傾斜照射聚焦於催化劑層 上。另’當基底材料為透明材料時，該雷射光束也可 聚焦後照射基底的反面，由於本發明實施例基底採用 透明材料，該雷射光束能量可迅速透過基底傳遞到催 化劑層並加熱催化劑。 反應預定時間後，由於催化劑的作用，通入到基 底附近的碳源氣在一定溫度下熱解成碳單元（c=c或 c)與氫氣。其中，氫氣會將被氧化的催化劑還原，碳 單元吸附於催化劑層表面，從而生長出奈米碳管。本 實施例中，由於採用雷射作為加熱熱源，且利用含碳 催化5=1彳層吸收雷射能量的作用，該化學氣相沈積法反 應溫度可低於600攝氏度。 本發明實施例採用上述含碳的催化劑層有以下優 點：第一，該含碳催化劑層可有效吸收雷射能量並加 熱催化劑，以使得該催化劑層更容易達到生長奈米碳 200828399 ♦官所，溫度丄第二，該含碳催化劑層可削弱雷射場強 度可在疋私度上避免雷射正面照射破壞新生長出 來的不米石反&，第三，該含碳催化劑層在反應過程中 可釋放碳原子促進奈米碳管的成核及生長。 另田採用田射聚焦反面照射基底生長奈米碳管 陣列可有錢免雷射光束正面照射破壞奈米碳管陣 ^且1雷射光束也不會與參與奈米碳管生長反應的 ^ _進订任何直接作用，不會對氣體的性質進行影 曰進而破壞奈米碳管陣列的生長。 乎二由於本發明實施例採用雷射趣 二厌5 ’催化劑局部溫度在較短時間内能夠被加 …、並吸收足_能量，_，碳源氣為直接通入到被 $熱的催化劑表面附近。因此，本發明實施例無需一 密封的反應室，即可同時保證生長奈米碳管陣列的催 $劑附近達到所需的溫度及碳源氣的密度，且，由於 &源乳分解產生的氫氣的還原作用，可確保氧化的催 化劑能夠被還原，並促使奈米碳管陣列生長。 請參閱圖2,本發明實施例依照上述方法以聚焦後 直徑範圍在50〜2〇〇微米的雷射光束垂直照射在玻璃 基底的催化劑上約5秒鐘，可得到如圖2所示的奈米 反笞％發射陰極。該場發射陰極包括一基底、一導^ 薄膜作為電極層以及奈米碳管陣列作為場發射端，其 中的奈米碳管陣列為山丘形狀，且垂直於基底生長。 該奈米碳管陣列的直徑為50〜80微米，高度為1〇〜2〇 11 200828399 . 微米。每個奈米碳管的直徑為40~80奈米。 • 請參_ 3，本發明實施難照上衫法在同-美 :上=照預定圖案用雷射光束多:欠照射在細 ==，可得到如圖3所示的場發射陰極陣列。 該％發射陰極陣列包括多個場發射陰極按照預定圖 案排列於同一基底，每—個場發射陰極都包括一個夺 米碳管陣列。 、綜上所述，本發明確已符合發明專利之要件，遂 依法提出專利申請。惟，以上所述者僅為本發明之較 佳實施例，自不能以此限制本案之申請專利範圍。舉 凡热‘本案技藝之人士援依本發明之精神所作之等 政修飾或變化，皆應涵蓋於以下申請專利範圍内。 【圖式簡單說明】 圖1係本發明實施例場發射陰極的製備方法的流 程示意圖。 圖2係本發明實施例獲得的奈米碳管場發射陰極 的掃描電鏡照片。 圖3係本發明實施例獲得的奈米碳管場發射陰極 陣列的掃描電鏡照片。 【主要元件符號說明】 無 12200828399 • Nine, invention description: [Technical field of invention] The present invention relates to a method for preparing a field emission cathode, and more particularly to a method for preparing a field emission cathode based on a carbon nanotube. VIII [Prior Art] Nano-stone anti-official system - a new type of carbon material, which has extremely excellent conductivity month b, and its tip with a near-theoretical limit is small, and its local electric field is more concentrated) Carbon Tube === The field emission material 'which has a very low field emission voltage, can transmit a very large current density' and is extremely stable in current' is therefore very suitable as a component of a field emission display. x The carbon nanotubes used for the radiating element are generally carbon nanotubes grown by arc discharge or chemical vapor deposition (CVD). The method of applying a carbon nanotube to a field emission display is to print a conductive paste or an organic binder containing a carbon nanotube into a pattern, and the carbon nanotube can be immersed from the slurry by subsequent processing. The head is exposed to form an emitter. In this method, the conductive paste containing the carbon nanotubes is coated on the conductive substrate by printing on a thick film steel plate, and the carbon nanotubes are bent in the slurry, interlaced with each other, and are not easily opened. The carbon nanotubes of the substrate are formed to have a good performance of the emission tip, and the carbon nanotube array is subjected to subsequent treatment, that is, a layer of the slurry is peeled off, so that the carbon nanotubes are exposed from the burial of the slurry and become the emission. However, stripping this slurry layer is very damaging to the carbon nanotubes. In addition, in the carbon nanotube layer prepared by the above method, the carbon nanotubes are substantially on the conductive substrate, and the number of carbon nanotubes perpendicular to the conductive substrate is less. Ran 6 200828399 'And 'nano carbon nanotubes as field emitters, from the end of the carbon nanotubes in the axial direction _ ^ electrons, so the carbon nanotubes on the conductive substrate is not conducive to the carbon nanotube field The performance of the launch. It is necessary to provide a method for preparing a carbon nanotube field emission cathode which can scream the above disadvantages, which does not damage the carbon nanotubes, so that the carbon nanotube field emitter is substantially perpendicular to the conductive substrate. To ensure that the carbon nanotube field emission performance is good. SUMMARY OF THE INVENTION A method for preparing a field emission cathode includes the steps of: & providing a substrate; forming a conductive thin film layer on the surface of the substrate; forming a carbon-containing catalyst layer on the conductive thin film layer; and introducing a carbon source A mixed gas of gas and carrier gas flows through the surface of the catalyst layer; and a laser beam is focused on the substrate to grow an array of carbon nanotubes to form a field emission cathode. Compared with the prior art, the method for preparing a field emission cathode uses a carbon-containing catalyst layer for a laser-assisted chemical vapor deposition growth of a carbon nanotube array. The catalyst layer can effectively absorb the laser energy and heat the catalyst, can weaken the intensity of the laser field, and can prevent the laser from destroying the newly grown carbon nanotubes to some extent; meanwhile, the field obtained by the preparation method of the field emission cathode The array of carbon nanotubes in the emitter cathode is perpendicular to the substrate and therefore has good field emission properties. [Embodiment] Hereinafter, the present invention will be further described in detail with reference to the accompanying drawings. Referring to FIG. 1, a method for manufacturing a field emission cathode according to an embodiment of the present invention 7 200828399 • The following steps are mainly included: • Step 1: Provide a substrate. In this embodiment, the base material is made of a material resistant to southermost materials. According to different applications, the base material in this embodiment may also be selected from transparent or opaque materials, for example, when applied to semiconductor electronic devices, opaque materials such as tantalum, cerium oxide or metal materials may be selected; when applied to large-area flat panel displays In the case, a transparent material such as glass or a plastic organic material is preferable. Step 2: forming a conductive film on the surface of the substrate. The electroconductive thin film may be formed on the surface of the substrate by thermal deposition, electron beam deposition or deposition. In this embodiment, the conductive film material is preferably an indium tin oxide film having a thickness of 10 to 100 nm, preferably 30 nm. Step 3: forming a carbon-containing catalyst layer on the above conductive film. In this embodiment, the method for preparing the carbon-containing catalyst layer comprises the steps of: providing a mixture of a dispersing agent and a carbonaceous material, and mixing with a solvent to form a solution; and subjecting the solution to ultrasonic dispersion treatment; after the dispersing The solution of the metal nitrate is added to dissolve the solution to obtain a catalyst solution; the catalyst solution is uniformly applied to the above conductive film; and baked to form a carbon-containing catalyst layer. Wherein, the carbonaceous material comprises a carbonaceous material such as carbon black or graphite. The dispersant is used to uniformly disperse the carbonaceous material, preferably dodecyl 8 200828399 Sodium Dodecyl Benzene Sulfonate (SDBS). The solvent can be selected from an ethanol solution or water. The mass ratio of the dispersing agent to the carbonaceous material is 1:2 to 1:10. In this embodiment, preferably 0 to 100 mg of sodium dodecylbenzenesulfonate and 100 to 500 mg of carbon black mixture and ethanol solution. Mix to form a solution. The metal resulphate compound includes sulphuric acid (Mg(N〇3)2 · 6H2O) and iron oxalate (Fe(N〇3)3.9H2〇), and oxalic acid (Co(N〇3)2 , 6H2 〇) or a mixture of nickel tartaric acid (Ni (Ν〇3) 2 · 6H 2 O) or a mixture of several components. 〜1〜1〜1〜1〜1〜1〜1〜1〜1〜1〜1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 0摩尔。 [Mol / L) of the stone acid acid and 0. 01~0. 5Mol / L of wall iron. The baking temperature is 60 to 100 °C. The effect of baking is to evaporate the solvent in the catalyst solution to form a carbon-containing catalyst layer. In this embodiment, the carbon-containing catalyst layer has a thickness of 10 to 100 μm. The catalyst solution is applied to the surface of the substrate by spin coating at a rotational speed of 1000 to 5000 rpm, preferably 1500 rpm. Step 4: a mixed gas of carbon source gas and carrier gas is passed through the catalyst. Layer surface. The carbon source gas is preferably an inexpensive gas acetylene, and other hydrocarbons such as decane, ethane, ethylene or the like may also be used. The carrier gas is preferably argon, and other inert gases such as nitrogen may also be used. In this embodiment, the carbon source gas and the carrier gas can be directly introduced into the vicinity of the surface of the chemical layer through a gas nozzle. The ratio of the aeration flow rate of the carrier gas to the source gas is 5:1 to ίο··1, and this embodiment is preferably argon gas of 200 standard cc/min (seem) and acetylene of 25 sccm. Step 4: Focusing the laser beam on the heated catalyst layer to grow the carbon nanotube array to obtain a field emission cathode. In this embodiment, the laser beam can be generated by a conventional argon ion laser or carbon dioxide laser having a power of 〇 5 watts (W), preferably 470 mW. The generated laser beam can be directly focused on the surface of the above catalyst layer by focusing on a lens. It can be understood that the laser beam can be focused on the catalyst layer by vertical irradiation or oblique irradiation. Alternatively, when the substrate material is a transparent material, the laser beam can also be focused to illuminate the opposite side of the substrate. Since the substrate of the embodiment of the invention employs a transparent material, the laser beam energy can be rapidly transmitted through the substrate to the catalyst layer and heat the catalyst. After the reaction for a predetermined period of time, the carbon source gas introduced into the vicinity of the substrate is pyrolyzed into a carbon unit (c = c or c) and hydrogen at a certain temperature due to the action of the catalyst. Among them, hydrogen will reduce the oxidized catalyst, and the carbon unit adsorbs on the surface of the catalyst layer to grow a carbon nanotube. In this embodiment, the reaction temperature of the chemical vapor deposition method can be lower than 600 degrees Celsius because the laser is used as the heating heat source and the carbon energy is used to catalyze the absorption of the laser energy by the 5=1 layer. The embodiment of the present invention adopts the above carbon-containing catalyst layer to have the following advantages: First, the carbon-containing catalyst layer can effectively absorb the laser energy and heat the catalyst, so that the catalyst layer can more easily reach the growth nano carbon 200828399 ♦ Temperature 丄 second, the carbon-containing catalyst layer can weaken the intensity of the laser field to prevent the frontal irradiation of the laser from damaging the newly grown non-meter stone reverse &amp; third, the carbon-containing catalyst layer in the reaction process The release of carbon atoms promotes the nucleation and growth of carbon nanotubes. Ueda uses the field-projected focusing and back-illuminated substrate to grow the carbon nanotube array. The laser beam can be used to illuminate the nano-carbon nanotube array. The laser beam will not react with the carbon nanotube growth reaction. Any direct effect of the ordering does not affect the properties of the gas and thereby destroy the growth of the carbon nanotube array. According to the embodiment of the present invention, the local temperature of the catalyst can be added in a short time, and the foot source energy is absorbed, and the carbon source gas is directly passed to the surface of the hot catalyst. nearby. Therefore, the embodiment of the present invention does not require a sealed reaction chamber, and can simultaneously ensure the temperature and the density of the carbon source gas in the vicinity of the catalyst for growing the carbon nanotube array, and is caused by the decomposition of the & source milk. The reduction of hydrogen ensures that the oxidized catalyst can be reduced and promotes the growth of the nanotube array. Referring to FIG. 2, in the embodiment of the present invention, a laser beam having a diameter of 50 to 2 〇〇 micrometers after focusing is vertically irradiated on the catalyst of the glass substrate for about 5 seconds according to the above method, and the nanometer shown in FIG. 2 can be obtained. The meter 笞% emits the cathode. The field emission cathode comprises a substrate, a thin film as an electrode layer and a carbon nanotube array as a field emission end, wherein the carbon nanotube array is in the shape of a hill and grows perpendicular to the substrate. The carbon nanotube array has a diameter of 50 to 80 microns and a height of 1 〇 to 2 〇 11 200828399 . Each carbon nanotube has a diameter of 40 to 80 nm. • Please refer to _ 3, the implementation of the difficult-to-wear shirt method of the present invention in the same - US: upper = according to the predetermined pattern with a large number of laser beams: under-irradiation in fine ==, can obtain the field emission cathode array shown in Figure 3. The %-emitting cathode array includes a plurality of field emission cathodes arranged in a predetermined pattern on the same substrate, each of the field emission cathodes including an array of carbon nanotubes. In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application in this case. Any modification or change in the spirit of the present invention by a person skilled in the art of the present invention shall be covered by the following patent application. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic flow chart showing a method of preparing a field emission cathode according to an embodiment of the present invention. Fig. 2 is a scanning electron micrograph of a carbon nanotube field emission cathode obtained in an embodiment of the present invention. Figure 3 is a scanning electron micrograph of a carbon nanotube field emission cathode array obtained in an embodiment of the present invention. [Main component symbol description] None 12