以氙氣作為單原子針離子發射源之研究

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2015

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Abstract

本實驗利用場離子顯微鏡(Field Ion Microscope, FIM),並使用本實驗室製作的附銥鎢單原子針作為場發射源,探討以氙氣作為氣體離子源的離子電流特性,並與氦氣離子源互相比較。 我們透過液態氮降溫針尖,並量測在不同溫度下,氙氣離子的飽和電流值,發現溫度降低接近至150 K附近時,離子電流有急遽增加 的趨勢,推測最佳工作溫度應為150 K以下附近。之後量測氙氣離子束的電流穩定性,與氦氣離子束的電流穩定性相當。透過以氙氣作為成像氣體的單原子針影像,計算出其離子束的張角小於1度,是非常集中的離子源,且角強度及亮度也有很好的表現。 氙氣離子束在150 K的工作溫度下,與氦氣離子束在22 K的工作溫度下的能力相近。若希望將氣體場發射離子源(Gas Field Ion Source, GFIS)應用在二次質譜儀(Secondary Ion Mass Spectroscopy, SIMS),則氙氣就具有成為此種離子源的潛力。
Xenon gas is the ion source of gas field ion source (GFIS), which emitter is the Ir/W<111>single atom tip in this research. We found the properties of xenon ion beam, and compared with helium ion beam. We used liquid nitrogen to cool the tip, and measured the saturation ion current of xenon in different tip’s temperature. We found that when the temperature was approaching 150K, the ion current was increasing quickly. We guessed the optimum temperature for xenon ion beam is below 150K. Then we measured the stability of xenon ion beam. It’s as good as helium ion beam. Finally we calculated the open angle of xenon ion beam, which was in 1 degree, by its image in the field ion microscopy. It’s also has a good angular intensity and brightness. Xenon ion beam has the same ability in 150K with helium ion beam in 22K. If we want to apply the GFIS in secondary ion mass spectroscopy (SIMS), xenon is the good choice for it.

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單原子針, 場離子顯微鏡, Single atom tip, Field ion microscope

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