|摘要: ||我們使用X光光譜與穿透式電子顯微鏡等方法, 對鑽石薄膜進行鍵結與微結構的探討. 控制化學氣相沉積法(CVD)製作鑽石薄膜的條件, 如電漿氣體的組合、溫度與壓力、外加偏壓等方式可以長出不同晶域大小的鑽石薄膜. 藉由近邊緣x光吸收精細結構(NEXAFS)對微米結晶鑽石(MCD)、奈米結晶鑽石(NCD)與超奈米結晶鑽石(UNCD)薄膜進行分析, 發現隨著鑽石薄膜晶域的減小, sp2對sp3的吸收強度比值增加. 再以as-grown、空氣電漿、氫氣電漿與偏壓不同表面處理的UNCD薄膜, 其中加偏壓處理的鑽石薄膜, 它的sp2對sp3的吸收強度比值最高. 所以隨著sp2對sp3吸收強度比值的增加, 電子場發射的啟動電場減少, 而電流密度增加做有系統的變化. 經過高能量的金離子照射之MCD與UNCD薄膜, 使用NEXAFS與TEM及其電子能量損失光譜(EELS)來進行研究. 發現MCD薄膜在照射後的晶域變小, 同時在晶域的周圍觀察到非晶碳相增加. UNCD薄膜在照射後, 晶域結構並沒有明顯的改變, 但在晶界中發現石墨相增加. 另外, 我們也觀察到UNCD薄膜場發射的啟動電場與金離子照射劑量呈現一個有系統的變化, 這個現象提供了一個做為輻射偵測材料應用的可能性.|
X-ray spectroscopy and transmission electron microscopy were utilized to study the electronic property and microstructure of diamond thin films. The grain size of diamond films grown by chemical vapor deposition (CVD) can be controlled by varying the synthesizing conditions, such as plasma gas composition, temperature, pressure and the applied bias voltage. Near edge x-ray absorption fine structure (NEXAFS) measurements indicate that the intensity ratio of sp2 to sp3 (sp2/sp3) increases with decreasing grain size of diamond films. The sp2/sp3 ratio of UNCD films can be adjusted by post deposition surface treatments. The bias voltage treated film has the highest sp2/sp3 ratio compared to the as-grown, air plasma or hydrogen plasma treated films. The sp2/sp3 ratio is related to the turn on field (E0) of electron field emission (EFE) and the electron current density (Je). Samples with the higher sp2/sp3 ratio are found to have the lower E0 and the higher Je. The TEM and EELS studies of high energy Au-ion irradiated diamond films indicate that some diamond grains in MCD are disintegrated and the amorphous carbon phase around the grain increases due to the ion irradiation. On the other hand, in Au-ion irradiated UNCD films, graphite and other carbon phases around the grains increase and there are no significant changes in grain size. It is also observed that, in UNCD, there is a systematic correlation between the fluency of Au-ion and the EFE properties (E0 and Je). This phenomenon facilitates a potential application of UNCD films as a radiation detection material.