SrRuO3 (SRO) 廣泛用於多層膜系統的導電層，是鐵磁性材料，其轉變溫度大約在165K。此材料有許多物理特性尚未知道原因，例如鐵磁性的來源、傳輸特性與效應、費米面下的Weyl fermion nodes等，其中SRO薄膜之霍爾效應研究，令許多人感到興趣。我們知道霍爾電阻率是由一般項及異常霍爾項組成，在過去文獻中我們發現有兩個問題: (一)在SRO薄膜中，低溫時之異常霍爾效應出現異常霍爾導電率變號的機制，雖有不同的理論觀點，但至今仍有爭議。由於物質中都有缺陷或雜質，有學者認為可能是電子和雜質散射所導致，而有skew-scattering與side-jump scattering理論，後來也有另一派的說法是與Berry Phase有關，是來自物質本身的性質，與外在的因素(雜質、缺陷散射)較無影響。近年來也有人提出是在費米面下Weyl nodes所貢獻；(二)在一般霍爾效應部份，發現霍爾係數在低溫時是負號，表示由電子主導，到了高溫後變為正號，表示由電洞主導。此符號改變的問題目前也無確切的原因來解釋，且沒有任何模型理論來擬合。本實驗的研究目標是希望解決問題(二)中霍爾係數變號的原因，以及提出一個全新理論模型來探討。
因此本實驗首先以脈衝式雷射沉積系統(Pulsed Laser Deposition, PLD)成長薄膜，厚度分別為181nm、275nm來精確量測，由X光繞射分析顯示其為品質良好的單晶薄膜。對於本次霍爾效應量測的結果相較於其他論文外加大磁場(8Tesla)實驗，我們在磁場1Tesla下即可看到低溫時有明顯的異常霍爾效應，且數據點也完整呈現。藉由霍爾係數對溫度的變化圖，我們發現其變號之溫度點並非在居禮溫度(TC)附近，且在高溫都會有一最大值出現。對於此變化我們提出一個新的模型: two-band model + impurity state來解釋，其中impurity state是變號的關鍵，且其位置必須在費米能階附近而且與導帶及價帶有強關聯，才能達到載子變號的結果。
目前對此問題已有新的方向與進展，但是我們仍需探討在SRO薄膜中，impurity state是來自薄膜中的哪個部分，可能是因為成長過程中有Ru原子空缺或是還有其他原因所導致，在未來仍有許多細節需要研究。

SrRuO3 (SRO), which exhibits a ferromagnetic transition around 165K, is widely used as a conduction layer in multilayer system. However, the origin of FM, transport properties and the effect of Weyl fermion nodes below Fermi surface are still unknown. In addition, many people are also interested in the result of Hall measurement. During literature review, we found that there are still two unsolved problems. The first problem is about the physical mechanism of the anomalous Hall conductivity dependence with temperature in SRO films. Two different theories have been proposed to explain it. Since there are defects or impurities in a material, some researchers believe that it might be due to electron or impurity scattering, such as skew-scattering and side-jump scattering theory. However, in recent years there is another theory associating with Berry Phase mechanism, which is from the intrinsic nature of the material. In 2014, it has been suggested that the anomalous Hall conductivity partially contributed by Weyl nodes under the Fermi surface. The second problem is about ordinary Hall coefficient (RH) which exhibits a sign change from negative to positive with the increase of temperature ie. the charge carrier is changing from electron-like to hole-like. There is no exact reason and no complete model to describe this phenomenon. Therefore, the goal of our experiment is to solve the second problem about the sign reversal of RH.
We have grown films of thickness 181nm and 275nm by pulsed laser deposition (PLD) technique. The X-ray diffraction results show that it is a good quality single crystal film. We have done Hall measurement from low temperature to high temperature with varying magnetic field up to maximum of 1 Tesla. We can see a clear square loop which proves anomalous Hall effect at low temperature. The Hall coefficient versus temperature plot (RH-T) is found to independ of Curie temperature (TC) and always exhibits a maximum value at high temperature. Finally, we propose a new theoretical model about two-band model along with impurity state to explain the whole situation. We find that the impure state is the key to cause the sign reversal, must be near the Fermi level and strongly coupled with conduction and valence bands. At present, we have a completed progress on this issue, but we still need to explore what is the origin of impurity state in the SRO films which may be due to Ruthenium vacancies generated during growth or to other unknown reasons. Further study is needed, and there are many challenges ahead for us to overcome.

論文審定書 i
誌 謝 ii
摘 要 iii
Abstract v
目 錄 vii
圖 次 ix
前言、文獻回顧 1
1-1 前言 1
1-2 文獻回顧 2
第二章 基本理論介紹 7
2-1 磁性物質的簡介 [17] 7
2-1-1 順磁性(Paramagnetic) 8
2-1-2 反磁性(Diamagnetic) 9
2-1-3 鐵磁性(Ferromagnetic) 9
2-1-4 反鐵磁性(Anti-ferromagnetic) 11
2-2 霍爾效應原理 12
2-3 SrRuO3材料特性 14
第三章 實驗方法、量測系統 17
3-1 SrTiO3(001)基板清洗 17
3-2 薄膜成長 18
3-3 光學微影製程 19
3-4 電性量測 22
3-4-1 霍爾量測 23
3-5 脈衝式雷射鍍膜系統(Pulsed Laser Deposition) 24
3-6 磁性量測 26
第四章 實驗結果與討論 27
4-1 電性量測 (RT Measurement) 27
4-2 晶體結構分析(XRD、RSM) 29
4-3 霍爾量測(Hall Measurement) 31
4-4 磁性量測 41
4-4-1 M-T 42
4-4-1 M-H 43
第五章 結論 46
參考資料 47
附錄 50

[1] G. Cao, S. McCall, M. Shepard, J. E. Crow and R. P. Guertin, Phys. Rev. B, 1997, 56, 321.
[2] Mackenzie, A. P., J.W. Reiner, A.W. Tyler, L.M. Galvin, S. R. Julian, M. R. Beasley, T.H. Geballe, and A. Kapitulnik, 1998, Phys. Rev. B 58, R13 318.
[3] Klein, L., J. S. Dodge, C. H. Ahn, G. J. Snyder, T.H. Geballe, M. R. Beasley, and A. Kapitulnik, 1996, Phys. Rev. Lett. 77, 2774.
[4] W. S. Chang, H. J. Liu, V. T. Tra, J. W. Chen, T. C. Wei, W. Y. Tzeng, Y. Zhu, H. H. Kuo, Y. H. Hsieh, J. C. Lin, Q. Zhan, C. W. Luo, J. Y. Lin, J. H. He, C. L. Wu, and Y. H. Chu, ACS Nano 8, 6242 (2014)
[5] D. Popescu, B. Popescu, G. Jegert, S. Schmelzer, U. Boettger, and P. Lugli, IEEE Trans. Electron Devices 61, 2130 (2014).
[6] A. Vorobiev and S. Gevorgian, Appl. Phys. Lett. 104, 222905 (2014).
[7] G. Koster, L. Klein, W. Siemons, G. Rijnders, J. S. Dodge, C. B. Eom, D. H. A. Blank, and M. R. Beasley, Rev. Mod. Phys. 84, 253 (2012).
[8] Z. Fang, N. Nagaosa, K. S. Takahashi, A. Asamitsu, R. Mathieu, T. Ogasawara, H. Yamada, M. Kawasaki, Y. Tokura, and K. Terakura, Science 302, 92 (2003).
[9] R. Mathieu, A. Asamitsu, H. Yamada, K. S. Takahashi, M. Kawasaki, Z. Fang, N. Nagaosa, and Y. Tokura, Phys. Rev. Lett. 93, 016602 (2004).
[10] R. Shimano, Y. Ikebe, K. S. Takahashi, M. Kawasaki, N. Nagaosa, and Y. Tokura, Europhys. Lett. 95, 17002 (2011).
[11] Bern, Francis, et al. "Hall effect of tetragonal and orthorhombic SrRuO3 films." physica status solidi (RRL)–Rapid Research Letters 7.3 (2013): 204-206.
[12] Gausepohl, S. C., et al. "Hall-effect sign reversal in CaRuO 3 and SrRuO 3 thin films." Physical Review B 54.13 (1996): 8996.
[13] Singh, David J. "Electronic and magnetic properties of the 4 d itinerant ferromagnet SrRuO3." Journal of applied physics 79.8 (1996): 4818-4820.
[14] Tan, Mingqiu, Xiangming Tao, and Junhui He. "First-principles study on the electronic and magnetic properties of perovskite ruthenate SrRuO3." Physica B: Condensed Matter 307.1-4 (2001): 22-27.
[15] Miao, Naihua, et al. "First-principles study of the lattice dynamical properties of strontium ruthenate." Journal of Physics: Condensed Matter 26.3 (2013): 035401
[16] Dodge, J. S., et al. "Temperature-dependent local exchange splitting in SrRuO 3." Physical Review B 60.10 (1999): R6987.
[17] Kittel, Charles, Paul McEuen, and Paul McEuen. Introduction to solid state physics. Vol. 8. New York: Wiley, 1996
[18] http://www.fhi-berlin.mpg.de/~hermann/Balsac/pictures.html
[19] https://slideplayer.com/slide/8392751/
[20] Weber, Dieter, et al. "Variable resistor made by repeated steps of epitaxial deposition and lithographic structuring of oxide layers by using wet chemical etchants." Thin Solid Films 533 (2013): 43-47.
[21] http://www.nanocenter.ndhu.edu.tw/ezfiles/71/1071/img/1566/197962869.pdf
[22] Yang, D., Tang, X., Wei, R., Hui, Z., Song, W., Zhu, X., & Sun, Y. (2016). Epitaxial growth of SrRuO3 thin films with different orientation by chemical solution deposition. Journal of Alloys and Compounds, 682, 154-159.
[23] Bohra, M., Wu, C. P., Yeh, H. J., Cheng, Y. H., Peng, C. C., & Chou, H. (2011). Role of Ru vacancies in the magnetism of strain relaxed SrRuO3 films on SrTiO3 substrates. Journal of Applied Physics, 109(7), 07D728.
[24] https://www2.nuk.edu.tw/cee/XPS.pdf
[25] Barlaz, D. E., Haasch, R. T., & Seebauer, E. G. (2017). Epitaxial SrRuO3/SrTiO3 (100) analyzed using x-ray photoelectron spectroscopy. Surface Science Spectra, 24(2), 024002.
[26] Kim, J., Chung, J., & Oh, S. J. (2005). In situ photoemission study on Sr Ru O 3∕ Sr Ti O 3 films grown by pulsed laser deposition. Physical Review B, 71(12), 121406.
[27] Park, J., Oh, S. J., Park, J. H., Kim, D. M., & Eom, C. B. (2004). Electronic structure of epitaxial (Sr, Ca) RuO 3 films studied by photoemission and X-ray absorption spectroscopy. Physical Review B, 69(8), 085108.
[28] Tan, Mingqiu, Xiangming Tao, and Junhui He. "First-principles study on the electronic and magnetic properties of perovskite ruthenate SrRuO3." Physica B: Condensed Matter 307.1-4 (2001): 22-27.
[29] Mazin, I. I., and David J. Singh. "Electronic structure and magnetism in Ru-based perovskites." Physical Review B 56.5 (1997): 2556.
[30] Klein, L., Reiner, J. R., Geballe, T. H., Beasley, M. R., & Kapitulnik, A. (2000). Extraordinary Hall effect in SrRuO 3. Physical Review B, 61(12), R7842.
[31] Ziese, M., & Vrejoiu, I. (2011). Anomalous and planar Hall effect of orthorhombic and tetragonal SrRuO 3 layers. Physical Review B, 84(10), 104413.
[32] Bern, F., & Ziese, M. (2013). Magnetotransport and Hall effect studies of SrRuO3/SrTiO3 superlattices. In EPJ Web of Conferences (Vol. 40, p. 15013). EDP Sciences.
[33] Xing, D. Y., and C. S. Ting. "Two-band model for anisotropic Hall effect in high-T c Y-Ba-Cu-O." Physical Review B 38.7 (1988): 5134.
[34] https://www.imperial.ac.uk/media/imperial-college/research-centres-and-groups/centre-for-bio-inspired-technology/7293202.PDF