不同晶粒大小及氮摻雜鑽石薄膜的拉曼光譜、紅外線光譜及功函數特性研究

本實驗?用微波電漿化學汽相?積法成長鑽石薄膜於矽基板上，所成長的鑽石薄膜晶?大小範圍從大約5 ?米(UNCD)至1 微米 (MCD)之間。這些?同晶?大小的鑽石薄膜是以甲烷/氬氣/氮氣及甲烷/氫氣的混合氣體，藉著改變氣體的比?、及成長時間等???控制晶?的成長。並且以電子掃瞄顯微鏡?決定晶?的半徑大小。這些成長的鑽石薄膜使用紫外光（325nm）及可?光（514nm） ?曼光譜進??測。非結晶SP2 鍵結的碳原子及SP3 鍵結的結晶鑽石的?曼散射強?隨著晶?大小的?同會有強?及?曼位移上的變化情形，並且此?曼強?也與入射光的能?有關。而位於1332cm-1 的鑽石?曼訊號與晶?尺寸大小的關係中可以發現，在微米級的鑽石薄膜中可以?測出但卻無法在15nm 晶?以下的鑽石薄膜觀察到。而對於?同入射光能?的?曼?測而言，因為可?光光子能?接近π 能態，所以只可激發SP2 態能階的碳原子。而紫外光光子能?較高，大於π 能態與σ 能態，而可同時激發SP2 及SP3 鍵結的碳原子，所以可以得到?測出SP3 鍵結的結晶鑽石訊號。此外，我們對鑽石薄膜表面進?酸化的處?，使其表面的鍵結改變。並且進?功函?的?測，發現功函?與表面的SP2 碳原子以及 CHx 的結構相關，這些功函?的變化我們以?曼光譜與紅外線光譜? 測?探討功函?變化原因，而對於?同摻雜的超?米結晶鑽石 (UNCD)而言，摻雜?的?同造成結構改變以及CHx 的變化，對於功函?的影響也在本?文中討?，由這些?測我們發現?米結晶鑽石 (UNCD)在成長方式以及所呈現出的結構及表面特性方面皆有許多? 於NCD、及MCD 的地方。

關鍵字

鑽石；拉曼光譜；紅外線光譜；功函數；晶粒大小

並列摘要

Microwave-plasma-chemical-vapor-deposition method was used to diamond films on silicon substrate with the size from 5 nm to 1μm. The different grain size diamond films has been synthesized by microwave plasmas fed with CH4/Ar/N2 and CH4/H2 mixtures by varying the proportion of gas mixtures and the growth time. Scanning electron microscope is used to determine the grain size of the grown diamond film. These diamond films have been examined by using ultraviolet (UV,325 nm) and visible (514nm) micro-Raman spectroscopy. Both the Raman intensity of amorphous sp2-bonded carbon and the strength of the 1332 cm-1 sp3-bonded diamond phonon are found to vary considerably as functions of the grain size of diamond film and the incident photon energy. The 1332 cm-1 diamond peak can be found in micro diamond and cannot be observed for grain size under 500nm in visible Raman spectroscopy. Visible Raman spectroscopy is more sensitive to sp2 sites,as visible photons preferentially excite their π states. UV Raman spectroscopy, with its higher photon energy, excites both the π and the σ states and so is able to probe both the sp2 and sp3 sites, allowing a direct probe of the sp3 bonding. After chemical acid cleaning procedure, oxygen ions were absorbed on the surface of diamond films. The oxygen adsorption caused the surface workfunction of diamond films down bending. The work function also shows a strong correlation with the grain size of diamond films.

並列關鍵字

diamond ； Raman Spectroscopy ； FTIR ； workfunction ； grain size

參考文獻

[1] F. C. Champion, “Electronic Properties of Diamonds” , U.K.London, Butterworths, (1963)

[2] M. W. Geis, J. A. Gregory, and B. B. Pate, “Capacitance-voltage measurements on metal-SiO2-diamond structures fabricated with(100)and (111)oriented substrates” , IEEE Trans. Electron Devices.38 (1991), 619-626

[3] W. Piekarczyk, “Crystal growth of CVD diamond and some of its peculiarities” , Crystal Research and Technology. 34 (1999),553-563

[4] Paul K. Chu, Liuhe Li, “Characterization of amorphous and nanocrystalline carbon film” , Materials Chemistry and Physics 96(2006), 253-277

[5] A. C. Ferrari, J. Robertson, “Origin of the 1150cm-1 Raman mode in nanocrystalline diamond” , Physical Review B 63 (2001),No.121405

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不同晶粒大小及氮摻雜鑽石薄膜的拉曼光譜、紅外線光譜及功函數特性研究

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