探討添加氬氣對「微米晶鑽石－超奈米晶鑽石」之特性的影響研究

Influence on characteristics of “micro-crystalline diamond/ultra nano-crystalline diamond” in addition of argon gas

江泓逸(Horng-Yi Chiang)

指導教授 ： 鄭秀鳳

國立臺灣師範大學/理學院/物理學系/碩士(2011年)

摘要

鑽石薄膜具有優異之物理、化學、機械性質，因而擁有甚高應用潛力，所以鑽石薄膜之合成為目前熱門之研究課題；尤其是鑽石薄膜具有好的電子場發射特性，適於製作場發射元件，更是重要的研究方向。而化學汽相沉積法(Chemical Vapor Deposition, CVD)是成長鑽石薄膜諸多方法中最廣為使用之合成技術。
本論文研究中，我們使用微波電漿輔助化學汽相沉積法(Microwave Plasma Enhanced Chemical Vapor Deposition, MPECVD)成長鑽石薄膜，探討在不同超奈米晶鑽石(UNCD)薄膜上成長微米晶鑽石(MCD)薄膜的生長機制、微結構特性及其對MCD/UNCD複合鑽石薄膜場發特性的影響。我們並使用拉曼光譜，場發射掃描電子顯微術(FESEM)，可見光發射光譜(OES)與穿透式電子顯微術(TEM)分析鑽石薄膜結構特性，以探討其成長機制。
本研究是首先在矽基板上成長一層超奈米晶鑽石(UNCD)薄膜作為晶核，再沉積一層微米晶鑽石(MCD)薄膜以合成MCD/UNCD複合鑽石，並探討第二階段沉積微米晶鑽石製程對MCD/UNCD複合鑽石場發特性的影響。第一部分的研究探討在氫氣/甲烷電漿中添加不同比例氬氣之效應；可以發現在添加50 %氬氣時，MCD/UNCD複合式鑽石有最佳之電子場發射特性：(MCD50)1h/UNCD1h薄膜之起始電場為6.50 V/μm；(MCD50)1h/UNCD3h薄膜之起始電場為5.0 V/μm。從TEM分析知是由於其含有較其他添加比例來得多的MCD/UNCD雙相晶，使得晶界形成奈米石墨相所致。第二部分的研究探討當選定50 %的氬氣添加為最佳化的鍍膜參數後，改變沉積MCD時間的效應，發現沉積一小時的MCD/UNCD複合鑽石薄膜，仍舊擁有最佳之場發射特性。
本研究所開發之MCD/UNCD複合鑽石薄膜最佳場發射性可以達到：起始電場為5.0 V/μm；在27.5 V/μm外加電場，場發射電流密度可達0.70 mA/cm2。

關鍵字

超奈米晶鑽石 ； 微米晶鑽石 ； 電漿輔助化學汽相沉積法 ； 可見光發射光譜 ； 穿透式電子顯微術

並列摘要

Diamond films possess excellent physical, chemical, and mechanical properties, such that the syntheses of diamond films have been the focus of research. Moreover, the diamond films own marvelous field emission properties and have great patential for the application on the electron field emission devices. The chemical vapor deposition (CVD) has been the most widely utilized process for growing the diamond films.
In this study, we used microwave plasma enhanced chemical vapor deposition (MPECVD) technique to synthesize microcrystalline diamond/ultrananocrystalline diamond (MCD/UNCD) composite films, for the purpose of investigating the growth mechanism and the related microstructural characteristics of the MCD/UNCD composite films. We first grow ultrananocrystalline diamond (UNCD) thin films as nucleation layers, followed by a secondary MPECVD process for growing microcrystalline diamond (MCD) thin films. We used Raman spectroscopy, field emission scanning electron microscopy (FESEM), optical emission spectroscopy (OES), and transmission electron microscopy (TEM) to characterize the MCD/UNCD thin films. The growth mechanism was discussed based on these investigations.
In the first part of research, different proportion of argon (0-90 %) was added into CH4/H2 plasma for the deposition of the secondary MCD layer. Among them, the 50% Ar plasma results in the best electron field emission properties, that is, the turn-on field of 6.50 V/μm for (MCD50)1h/UNCD1h and of 5.0 V/μm for (MCD50)1h/UNCD3h films. TEM examinations indicated that the two step MPECVD process markedly modified the gannular structure of UNCD films, resulting in large-grain/small-grain duplex microstructure. In the second part of research, we changed the deposition time for growing the MCD layer (with 50% Ar plasma). We observe that 1 h deposition of MCD layer leads to the best electron field emission properties. The best electron field emission properties obtainable are：turn-on field of 5.0 V/μm with EFE current density of 0.70 mA/cm2 at an applied field of 27.5 V/μm.

並列關鍵字

UNCD ； MCD ； MPECVD ； OES ； TEM

參考文獻

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