臺灣博碩士論文加值系統

鈀(palladium)在鎢(111)上會造成皺化(faceting)已經被研究過的現象。所謂的皺化現象是由於bcc(111)本身就是較為不穩定的面，超過一層鈀(palladium)在鎢(111)經過退火(annealing)至700K~1100K，會露出能量較低的{112}面而形成遍佈不同大小的金字塔的表面。而鈮(niobium)的表面功函數較鎢來的低，並且又是一種超導材料，因此若能在鈮(111)的表面上發現皺化的現象。在電子的場發射、STM的針尖或離子鎗等應用的表現上會比鎢來的理想。在超高真空(約1 x 10-10 torr)的環境下，我們利用了低能量電子繞射(Low Energy Electron Diffraction, LEED)、可程式控溫歐傑能譜(Temperature Programmed Auger, TPA)，來研究氧(O)覆蓋層對於鈮(niobium)基板的影響，亦即PO/Nb(111)表面系統中，再利用LEED觀察是否有任何表面重構的現象發生並詳細分析此結構。

Abstract

The faceting induced by Pd on W(111) has been research a lot in our laboratory. The bcc(111) surface is an unstable surface. Once more than one monolayer Pd is deposited on it and annealing to 700K~1000K, the structure of surface will transfer from planar (111) to faceting{112}, and pyramids with different size are formed on the surface. The reason we want to study Nb is that the work function of Nb (4.87eV) is lower than that of W (5.25eV) [11] and Nb is one of the superconductive material. Thus, if the faceting structure can be induced on Nb(111). The performance of Nb tip will be better than W tip in applications, such as field emission, high resolution electron microscopes or field ion guns. In an ultrahigh vacuum (UHV) chamber with a base pressure of 1 x 10-10 torr, we have used Low Energy Electron Diffraction (LEED) and Temperature Programmed Auger (TPA) to study the effect of adsorbates on the surface structure of Nb(111). That is, in O/Nb(111) systems, we observe the structure of the surface with LEED to see if any surface reconstruction occurs after annealing and analyze the structure.

Contents
Chapter 1 Introduction………..……………………………………………………1
Chapter 2 實驗儀器及原理介紹.............................................................................3
2.1 真空腔及研究工具…………………………………………………………3
2.2 樣品製備.........................................................................................................4
2.3 低能量電子繞射儀(LEED) 介紹..................................................................7
Chapter3. 實驗結果.............................................................................................9
3.1 繞射圖形分析………………………………………………………………9
3.1.1鈮(Nb)之乾淨表面之繞射圖形分析……………………………………9
3.1.2鈮(Nb)皺化面之晶格結構分析………………………………………...11
3.2理想狀況下Spot position至Δk之轉換函數………………………………14
3.2.1 K-Spaces轉換…………………………………………………………...14
3.2.2 繞射亮點標定………………………………………………………….15
3.2.3鈮(Nb)之乾淨面G向量分析…………………………………………..17
3.2.3.1 厚度之光學校正…………………………………………………18
3.2.3.2外圍線段偏折問題修正………………………………………….19
3.2.3.3 磁場問題修正……………………………………………………20
3.2.3.4樣品偏離修正…………………………………………………….21
3.2.4鈮(Nb)曝氧(O2)之皺化表面G向量分析……………………………...27
3.3曝氧量分析………………………………………………………………….32
Chapter 4 .結論……………………………………………………………………….33
Chapter 5 參考文獻………………………………………………………………….34

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