我們運用X光吸收光譜近邊結構(XANES)研究β-FeSi2奈米粒子之尺寸與其電子結構及物理性質之相關性。在Fe K-edge光譜上觀察到奈米尺寸樣品的Fe 4p未佔據態相較於塊材明顯增加且主吸收峰的位置向低能量位移大約4.5 eV。在較低能量，距主峰約20 eV處有個強度較弱的峰為Fe 3d-Fe 4p混成軌域的貢獻，此峰的強度隨著尺寸減小有減弱的趨勢顯示Fe 3d-Fe 4p混成程度隨著尺寸減小而減少。在Fe L2,3-edge光譜觀察到Fe 3d未佔據態隨著尺寸減小而增加。在較高能量，距離主峰1.7 eV有個強度較弱峰為Fe 3d-Si 3p混成軌域的貢獻，此峰的強度隨著尺寸減小有減弱的趨勢顯示Fe 3d-Si 3p混成程度隨著尺寸減小而減少。在Si K-edge光譜上觀察隨著尺寸減小氧化矽明顯增加。我們推論β-FeSi2奈米粒子的磁性與奈米微粒內之Fe群聚有關。

We have performed x-ray absorption near edge structure (XANES) on β-FeSi2 nanoparticles to study the correlations between the particle size and their physical properties. Fe K-edge spectra indicates that the number of Fe 4p unoccupied states of nanoparticle samples are higher compared with the bulk sample. The main peak shifted 4.5 eV to the lower energy site. The small feature, contributed by Fe 3d-Fe 4p hybridized states at (~ 7115 eV), decreases as the samples size is decreased, which suggests that Fe 3d-Fe 4p hybridization decreases as the samples size is decreased. Fe L2,3-edge spectra indicates that Fe 3d unoccupied states increases as the samples size is decreased. The intensity of a small shoulder at about 1.7 eV to the higher energy site contributed by Fe 3d-Si 3p hybridized states, decreases as the samples size is decreased, suggesting that Fe 3d-Si 3p hybridization decreases as the samples size is decreased. Si K-edge spectra indicates that the silicon oxidation increases as the samples size is decreased. We conclude that the magnetic property of β-FeSi2 nanoparticles is related to the isolated Fe inside the particles.

第一章 序論 …………………………………..………….……….……1   
  1-1  金屬矽化物的發展……………………………………………..1
  1-2  研究動機…………………………………..………….…………2
第二章 樣品簡介 ………………………………………………………3  
 2-1 FeSi2樣品的製程 …………………………...………………….…3 
 2-2 FeSi2的特性…………………………………….………….………3  
 2-3 相關磁性的簡介………………………………….……………….9
第三章 X光吸收光譜…….……………………………………...….…14
3-1  X光吸收光譜近邊緣結構(XANES) …………………………18  
3-2  延伸X光吸收光譜精細結構（EXAFS） …………..………19  
3-3  數據分析 ……………………………………………...………21   
第四章 實驗設備與量測方法 …………………………….………… 27  
4-1  X光光源 ………………………………………………………27   
4-2  單色儀 ………………………………………...………………29  
4-3  光譜測量方式 ………………………………………..……… 29  
第五章  結果與討論 …………………………………………………33  
第六章  結論 …………………………………………………...…… 55
參考文獻 ……………………………………………………...……… 56

圖目錄
圖2.1 FeSi2在不同溫度下的像變化，上方表示為β-FeSi2下方表示α-FeSi…….……………………………………………………...…….....5
圖 2.2 α-FeSi2 的結構是意圖(tetragonal)……………………………..5
圖 2.3 β-FeSi2結構示意圖(orthorhombic)，圖中的a、b與c為其晶格常數……………………………………................................................5  
圖 2.4不同奈米尺寸的β-FeSi2與其塊材的X光繞射譜圖…..…….6
圖 2.5 不同奈米尺寸的β-FeSi2與其塊材的TEM圖………………7
圖 2.6 不同奈米尺寸的β-FeSi2與其塊材在不同溫度下量測的磁化率
………………………………………...……………………….................7
圖 2.7 不同奈米尺寸的β-FeSi2在低溫下量測apparent anisotropic constant。插圖(a)表示β-FeSi2尺寸40nm在5 K時有磁滯迴路而50 K時則沒有。插圖(b)表示在高磁場下M vs 1/H…………………..................................................................................8  
圖 2.8 不同奈米尺寸的β-FeSi2與其塊材在不同溫度下的比熱變化C/T vs T2。插圖表示當磁場增加spin glass-type會從低溫位移到高溫
………………………………....................................................................8
圖 2.9微觀下的磁性序列(每個粒子的磁矩)………………….…….10
圖 2.10沒有外部磁場時的順磁性物質的簡圖………………..……..12
圖 2.11在弱磁場中的順磁性物質的簡圖……………………………12
圖 2.12在強磁場中的順磁性物質的簡圖……...............................12  圖3.1 物質吸收截面與能量之關係圖………………………………...16
圖3.2 XANES與EXAFS分界圖………………………………………17
圖3.3 光電子平均自由路徑與能量關係圖…………………………...18
圖3.4 單一散射與多重散射之圖示…………………………...............19  圖3.5 出射電子受鄰近原子的背向散射，而產生干涉現象…….........20  圖3.6 X光吸收光譜之數據分析流程…………………………............21
圖3.7 選擇能量底限E0值的不同方法……………………..................23
圖4.1 X光吸收光譜實驗示意圖………………………………………28
圖4.2 穿透式………………………………………………..…….........30   圖4.3 X光通過物質之強度衰減……………………………................30 圖4.4 螢光式………………………..…………………………….........32圖4.5 電子逸出式…………………………………………………….32圖 4.6 光子吸收過程………………...…………………..……………32
圖5.1 (a)為Fe foil Fe K-edge近邊吸收光譜圖………………………..35
圖5.2不同尺寸的β-FeSi2與Fe2O3 Fe K-edge歸一化光譜圖…….36
圖5.3 β-FeSi2在不同奈米尺寸與塊材(bulk)的主吸收峰(A)的一次微分
……………………………………………………………………..……37
圖5.4 β-FeSi2在不同奈米尺寸與塊材(bulk)的小肩峰(B)與吸收起點能量位置的一次微分…………………………………………………..37
圖5.5β-FeSi2在不同奈米尺寸與塊材(bulk)與Fe foil Fe K-edge歸一化光譜圖……………………………………………… ………………….38
圖5.6 模擬Fe 3d-Fe 4p混成軌域的混成程度示意圖………………39
圖5.7不同尺寸的β-FeSi2 Fe L2,3-edge歸一化光譜圖………………44
圖 5.8 N. Antonov* and O. Jepsen利用local-density approximation(LDA)的計算模擬……………………………………45
圖5.9 Fe foil、FeSi β-FeSi2、α-FeSi2Fe L2,3-edge光譜圖的文獻…..45
圖5.10不同尺寸的β-FeSi2 Fe L2,3-edge扣除arc-tangent光譜圖…46
圖5.11不同尺寸β-FeSi2對L3-edge的一次微分……………………….47
圖5.12 不同尺寸β-FeSi2對L3-edge的二次微分………………………47
圖5.13 不同尺寸衛星峰(E)的面積比例………………………………48
圖5.14不同尺寸β-FeSi2、silicon foil與SiO2的Si K-edge歸一化光譜圖
………………...…………………………………………………….…..49
圖5.15 不同尺寸β-FeSi2 Si K-edge歸一化光譜圖…………...……….50
圖5.16 不同尺寸β-FeSi2 、FeO與Fe2O3 O K-edge歸一化光譜圖…...53
圖 5.17 SiO2 O K-edge光譜圖之文獻，圖中的TH-SiO2為高溫下成長的樣品，UV-SiO2為低溫下成長的樣品………………………………54

1.V. Bellani, G. Guizzetti, F. Marabelli, A. Piaggi, A. Borghesi, F.
Nava, V. N. Antonov, Vl. N. Antonov, O. Jepsen, O. K. Andersen,
and V. V. Nemoshkalenko, Phys. Rev. B 46, 9380 (1992).

2.V. K. Zatsev, S. V. Ordin, V. I. Tarasov, and M. I. Fedorov, Sov. Phys.Solid State 21, 1454 (1979).

3.Lianwei Wang, Linhong Qin, Yuxiang Zheng, Wenzhong Shen,
Xiangdong Chen, Xian Lin, Chenglu Lin, and Shichang Zou, Appl.
Phys. Lett. 65, 3105 (1994).

4.Castor Fu, M. P. C. M. Krijn, and S. Doniach, Phys. Rev. B 49,
2219 (1994).

5.E. Müller, C. Drasar, J. Schilz, and W. A. Kaysser, Mater. Sci. Eng., A
362, 17 (2003).

6.D. Leong, M. Harry, J. Reeson, and K. P. Homewood, Nature (London)
387, 686 (1997)

7.O. Kubaschewski, Iron-Binary Phase Diagrams (Springer, New York
1982), p. 136.

8.V. Jaccarino, G. K. Wertheim, J. H. Wernick, L. R. Walker, and S. Arajs,
Phys. Rev. B,160, 476 (1967).

9.Y. Dusausoy, J. Protas, R. Wandji, and B. Roques, Acta Crystallogr.,
Sect. B: Struct. Crystallogr. Cryst. Chem. 27, 1209 (1971).

10.M. E. Schlesinger, Chem. Rev. 90, 607 (1990).

11.V. Darakchieva, M. Baleva, M. Surtchev, and E. Goranova, Phys.
Rev. B 62, 13 057 (2000).

12.Z. Yang and K. P. Homewood, J. Appl. Phys. 79 (8), 15 April 1996

13.Y. Y. Chen, P. C. Lee,_C. B. Tsai, S. Neeleshwar C. R. Wang, J. C. Ho, H. H. Hamdehm, Appl.Phys. Lett 91, 251907 (2007)


14. 6H. H. Hamdeh, J. C. Ho, and S. A. Oliver, J. Appl. Phys. 81, 1851 (1997).

15. Milton mentions some inconclusive events (p.60) and still concludes that "no evidence at all of magnetic monopoles has survived" (p.3). Milton, Kimball A.（2006）．Theoretical and experimental status of magnetic monopoles．Reports on Progress in Physics，69（6）：1637-1711．
16. Guth, Alan（1997）．The Inflationary Universe: The Quest for a New Theory of Cosmic Origins．Perseus
17. X-Ray Absorption : Principles, Application, Techniques of EXAFS, SEXAFS, SEXAFS and XANES” , edited by D. C. Koningsberger, and R. Prins, Chem. Analysis Vol. 92 (Wiley 1988).
18. E. A. Stern, M. Newville, B. Ravel, Y. Yaceby, and D. Haskel, Phys. B. 208&209, 117 (1995).
19. D. E. Sayers, E. A. Stern, and F. W. Lytle, Phys. Rev. Lett. 27, 1024 (1971).
20. EXAFS and Near edge Structure , edited by A. Bianconi, L. Incoccia and S. Stipcich  (Springer-Verlay 1983).
21.D. E. Sayers, E. A. Stern, and F. W. Lytle, Phys. Rev. Lett. 27, 1024 (1971)
22. “Synchrotron Radiation Research”, edited by H. Winick, S. Doniach (1980).
23. 安全訓練手冊，新竹同步輻射.
24.C.S.Hwang,F.Y,Lin.et al.,Rev Sci.Instrum.69,1230(1998
25. Scott A. McHugo,  A.C. Thompson, G. Lamble, C. Flink, E.R. Weber, Physica B 273-274 (1999) 371-374
26. Scott A. McHugo,a) A. C. Thompson, A. Mohammed, and G. Lamble, J. Appl. Phys, 89(2001)8

27.H. Purdum, P. A. Montano, Phys. Rev. B, 25(1982)7

28. N. Tsujii, H. Yamaoka, H. Oohashi, I. Jarrige, D. Nomoto,
K. Takahiro, K. Ozaki, K. Kawatsura, Physica B 403 (2008) 922–924

29. D. Berling, G. Gewinner, M.C. Hanf, K. Hricovini, S. Hong, B. Loegel,
A. Mehdaoui, C. Pirri, M.H. Tuilier, P. Wetzel, Journal of Magnetism and Magnetic Materials 191 (1999) 331-338

30.Fausto Sirotti, Maurizio De Santis, Phys.Rev. B, 48(1993)11

31.S. Eisebitt, J. E. Rubensson, M. Nicodemus, T. Boske, Phys. Rev. B, 50(1994)24

32. V. N. Antonov* and O. Jepsen, Phys. Rev. B, 57(1998)15

33. J. Tani*, H. Kido Journal of Alloys and Compounds 352 (2003) 153–157

34. Z.J. Pan, L.T. Zhang ∗, J.S. Wu, Materials Science and Engineering B 131 (2006) 121–126

35. Shang-Di Mo, W. Y. Ching, App. Phy. Lett, 78(2001)24

36. Z Y Wu, F Jollet, F Seifert, J. Phys.: Condens. Matter 10 (1998) 8083–8092.

37. H. M. Tsai, S. C. Ray, C. W. Pao, J. W. Chiou, C. L. Huang, C. H. Du, and W. F. Pong, J. Appl. Phys, 103(2008)013704.

38. E.P. Domashevskaya , S.A. Storozhilov , S.Yu Turishchev , V.M. Kashkarov V.A. Terekhov , O.V. Stognej , Yu E. Kalinin , S.L. Molodtsov, Journal of Electron Spectroscopy and Related Phenomena 156–158 (2007) 180–185