超奈米微晶鑽石薄膜之微結構及電子場發射特性之研究

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Title:	超奈米微晶鑽石薄膜之微結構及電子場發射特性之研究
Other Titles:	Microstructures and electron field emission properties of ultra nanocrystalline diamond films
Authors:	陳皇欽;Chen, Huang-chin
Contributors:	淡江大學物理學系博士班林諭男;Lin, I-nan
Keywords:	電子場發射特性;成長機制;穿透式電子顯微鏡;electron field emission properties;growth mechanism;electron field emission properties
Date:	2010
Issue Date:	2010-09-23 16:06:13 (UTC+8)
Abstract:	本論文是以研究超奈米微晶鑽石薄膜場發射特性變化與微結構的改變為研究的主題，本論文分三個主題來解釋超奈米微晶鑽石結構的變化與場發射之間的關係。第一個主題，我們藉由超微量氫氣的添加與純氫氣電漿蝕刻鑽石薄膜表面，來研究超奈米微晶鑽石微結構變化與場發射的關係，並藉此探討鑽石同素異型體結構的產生；我們發現當添加氫氣參與超奈米微晶鑽石薄膜的成長時，會有鑽石顆粒逐漸變大的趨勢，當我們控制氫氣含量為0.03%時，可以明顯的藉由穿透式電子顯微鏡發現鑽石結構有stacking faults缺陷的產生，隨著氫氣的增加其鑽石結構缺陷的區域變得更為明顯，藉由高解析影像與選區繞射圖發現，鑽石缺陷的地方會有鑽石同素性型體的變化，從立方體結構轉變成六面體結構，相對的，電子場發射特性也隨著氫氣的添加而有逐漸減弱的趨勢；在純氫氣電漿處理鑽石薄膜研究中，也發現薄膜表面的超奈米微晶鑽石有結構結合的反應，並且其結構鍵結區相單晶化，而當我們添加1%甲烷在氫氣電漿中，發現與純氫氣電漿處理有不同的鑽石結構變化，具有超奈米微晶鑽石與微米微晶鑽石同存的現象，此現象造就了更佳的電子場發射特性。第二部份我們以不與碳產生反應的高能量銀離子與金離子照射超奈米微晶鑽石薄膜，試圖利用破壞性的方式去改變鑽石薄膜電子場發射特性，我們發現100 MeV的銀離子與2.245 GeV的金離子照射超奈米微晶鑽石薄膜後，電子場發射會隨著照射密的的增加而變好，藉由穿透式電子顯微鏡微結構的觀測中，發現5 nm的超奈米微晶鑽石顆粒，會有鑽石結構被破壞與再結晶這兩種變化，所以在微結構中可以發現有20~30 nm大顆粒的鑽石結構產生，並且鑽石顆粒邊界發現有石墨相與非結晶碳相的結構產生。第三部分我們試圖改變基板中間緩衝層鑽石成核的變化，以探討成長超奈米微晶鑽石薄膜之電子場發射特性的變化，我們利用36 KeV碳離子先照射矽基板，試圖在基板表面成長碳化矽結構，再成長超奈米微晶鑽石薄膜，發現電子場發射有不一樣的改變；我們再利用36 KeV的碳離子照射碳膜，試圖產生鑽石的成核結構以便鑽石薄膜成長，發現當我們利用碳分子(C2)照射碳膜後，鑽石薄膜電子場發射的特性為最佳。最後，我們利用化學氣相沉積法先成長一層的碳化矽薄膜結構在矽基板上，並且我們試著在矽(100)與矽(111)兩種基板上，研究在超奈米微晶鑽石薄膜成長後電子場發射特性的改變，我們發現當我們成長超奈米微晶鑽石薄膜/碳化矽/矽(100)時，具有最佳的電子場發射特性，這是因為電子容易在矽基板100方向時傳輸電子，所以容易讓更多電子發射到真空腔裡，產生最佳的電子場發射特性。 In this thesis, the correlation between the microstructure of ultra-nanocrystalline diamond (UNCD) films and their electron field emission (EFE) properties was investigated from 3 aspects: (i). microstructural modification via the incorporation of hydrogen species in the plasma or the lattices, (ii). heavy ion irradiation effect ; and (iii). utilization of buffer layer for enhancing the nucleation of UNCD. For the hydrogen effect, we observed the either incorporating the H2 into Ar-CH4 plasma or post-treating the UNCD films in H2-plasma induced the grain growth phenomenon. Addition of H2, even for a small amount of 0.033%, induced the anisotropic growth of diamond grains, in accompanying with the formation of (111) stacking faults. Incorporation of more abundant amount of H2 (>40%) induced the formation of hexagonal diamond (6H or 8H diamond), the isomorphous of 3C-diamonds. In contrast, post-treating the UNCD films in H2-plasma induced the Oswald-Ripening of the diamond grains. Both the grain growth phenomena eliminated the proportion of grain boundaries that suppress the electron conduction path and, thereafter, increased the turn-on field for EFE process. On the other hand, addition of 1%CH4 in H2 during the post-treatment process markedly lowered the turn-on field and enhanced the EFE current density. TEM examination revealed that the prime factor for improving the EFE process is the formation of nanographites among the nano-sized diamond grains. In the heavy ion irradiation effect: we irradiated the UNCD with Ag- or Au-ions to modify the microstructure of the films so as to enhance the EFE of the films. We observed the both 100 MeV Ag-ions and 2.245 GeV Au-ions markedly improved the EFE behavior for the UNCD films. TEM investigation revealed that large aggregates (~ 20 nm) of diamond clusters were induced among the 5 nm diamond grains due to the heavy on irradiation. Moreover, amorphous carbons and nano-graphites were resulted surrounding the aggregates, which are presumed to be the prime factor for improving the EFE properties due to heavy ion irradiation. Finally, we utilized buffer layer to enhancing the nucleation of diamond, investigating how the buffer layer modifies the EFE properties for the diamond films. We observed that implanting the Si-substrates with carbon species induced the formation of SiC particles, which enhanced the nucleation of diamond and improved the EFE properties of the films. Implanting C2 dimmer into amorphous carbons can also enhanced the nucleation of diamond and improved the EFE properties of the films. In contrast, pre-coating the Si-substrates with a thin layer of crystalline stoichiometric SiC can also modify the growth behavior of the diamond. Interestingly, the nature of Si-substrate, Si(111) or Si(100), alter the EFE properties in different manner, that is ascribed to the difference between the interlayer of the UNCD/SiC/Si films. While the SiC buffer on Si(100) substrates showed the improved EFE properties, that on Si(111) substrates degraded these behavior for the UNCD films.
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