過濾式電弧沈積類鑽石膜之場發射性質

Abstract

電子場發射元件應用在平面顯示器上已經被廣泛的研究。其工作原理和陰極射線管類似，但有輕、薄的優點，不需要如液晶顯示器的背光設計。FED由於採用低壓場發射陰極陣列激發磷光質玻璃版，具有高解析度、高對比、低耗電，且不受環境溫度所影響。因此，預測它將是下一代顯示器的主流。 為了達到低工作電壓和高發射電流的低消耗功率的目的，鑽石是最佳的材料之一。鑽石因為具有負電子親和力，相較於一般的金屬或矽製FEAs尖錐上被覆一層鑽石膜者，在相同的工作電壓下會有較高的工作電流。利用模型轉換技術 (Transfer Mold Technique) 所製成的金字塔型尖錐，不僅容易製造而且適合大面積化。因此，鑽石在場效發射陣列上之技術將是未來研究發展上的主流。 本實驗利用過濾式電弧沈積 （Filtered Arc deposition），藉由物理氣相沈積 （Physical Vapor Deposition）的方式，而能沈積均勻且大面積的非晶質類鑽石膜（Amorphous Diamond-Like Carbon）。同時可藉添加氮氣為摻雜 (dopand) 的氣體源，在刻有倒錐形金字塔之基板上沈積含氮非晶質類鑽石膜。沈積後的含氮非晶質類鑽石膜以掃描式電子顯微鏡 (SEM)、拉曼光譜儀 (Raman)、歐傑電子光譜儀 (AES)、與I-V量測系統來觀察表面型態、鑑定品質與鍵結和分析場發射特性。 經實驗結果顯示，場效發射陣列的電流-電壓值 (Ie - Va) 與鑽石膜的品質有很大的關係。當改變沈積參數時，非晶質鑽石膜的品質隨氮氣流量的上昇而變差，其成份漸由類鑽碳 (Diamond-like Carbon) 組織趨向石墨組織 (Graphite)，顯示類鑽碳的含氮量增加會增加類鑽碳結構的缺陷數目。其電流值也變得較大，由無含氮（電壓30V時電流23μA） 增加到低含氮量(電壓30V時電流82μA) 和高含氮量(電壓30V時電流142μA)。因此證明了非晶質鑽石 (a-Diamond) 組織的缺陷數目在場發射電流中扮演重要的角色。

Vacuum microelectronic devices apply on field emission displays are widely researched. It operate on similar principle as the cathod-ray tube (CRT) , but it has advantages as light, thin and need not backlighting for liquid crystal display used. FED used an array of low-voltage electron emitters to excite light-emitting phosphors that illuminate the screen which is high resolution, high contrast ratio, low power consumption and insensitive to temperature. So, we prefer it will be the dominant display in the future. In order to reach the properties of low operating voltage and high emission current for low power consumption, diamond is one of the best materials. Because of the negative electron affinity (NEA) property of diamond, compare with the metal or Si FEAs which are coated a diamond thin film on tips has higher operating current under the same operating voltage. The pyramidal-shape tips make by using transfer mold technique are either easy fabricated or suitable for large area application. Therefore, diamond apply in the FEAs will be the dominant technique in the future. The experience using the filtered arc deposition (FAD), by using the physical vapor deposition (PVD) technique, the uniformity and large area amorphous diamond-like carbon is successful deposited. By using nitrogen gas for dopant source at the same time, the amorphous diamond-like carbon films with contains nitrogen are deposited on the inverted pyramidal-shape SiO2 substrates. The deposited amorphous diamond-like carbon with contains nitrogen use scanning electron microscopy (SEM) , Rman spectroscopy, Auger electron spectroscopy (AES) and I-V measurement system to examine surface morphology, quality and bonding type and analyses field emission characteristic. From the results of experience, the current-voltage (Ia-Vg) value of field emission arrays has closely relation with the quality of diamond film. When deposition condition changes, the quality of amorphous diamond-like carbon get worse as the flow rate of nitrogen increase, the composition develop from diamond-like carbon to graphite gradually, it indicates that the contain of nitrogen increase the interior defects of diamond-like carbon structure increase. The current value become larger, the value increase from no nitrogen contain (Vg=30V, Ia=23mA) to low nitrogen contain (Vg=30V, Ia=82mA) and high nitrogen contain (Vg=30V, Ia=142mA). It is clear that the defects of amorphous diamond (a-D) structure play a very significant effect on emission current.