研究發現絕緣氧化物鋁酸鑭(Lanthanum aluminate, LaAlO3)成長在鈦酸鍶(Strontium titanate, SrTiO3)材料上的介面間會產生高導電的二維電子氣。這樣引人注目的介面特質使得這個異質結構材料一直被廣泛地研究。研究中證實鋁酸鑭和鈦酸鍶之異質結構，成長於鈦酸鍶之上的鋁酸鑭厚度必須大於4個單位晶胞。4個單位晶胞的鋁酸鑭和鈦酸鍶之間的介面才會導電。因此，吾人可以透過改變鋁酸鑭的厚度，控制鋁酸鑭與鈦酸鍶介面的電性表現。本工作主要研究目的是利用光照調控鋁酸鑭與鈦酸鍶之間的電子特性之表現。在3個單位晶胞的鋁酸鑭和鈦酸鍶之間的不導電介面，於3個單位晶胞的鋁酸鑭表面上成長奈米金團簇，透過光照的調控，進而改變鋁酸鑭與鈦酸鍶介面的電子特性。本研究利用掃描穿隧顯微鏡與掃描穿隧能譜，針對3個單位晶胞的鋁酸鑭和鈦酸鍶的異質結構氧化物，於鋁酸鑭和鈦酸鍶之間之介面處進行區域電子特性量測，並且比較材料在照光以及未照光的情況下，探討光如何調整鋁酸鑭和鈦酸鍶介面局域電性的變化。實驗結果清楚顯示材料在光照之後，其鋁酸鑭和鈦酸鍶異質介面的電性有變化。鋁酸鑭內建電場值由23 meVÅ-1調變為9 meVÅ-1；在異質介面處的鈦酸鍶方面，結果顯示能帶有向下彎曲的現象。能帶彎曲的能量大小為由0.0 eV 調變約為0.4 eV，能帶彎曲的範圍自介面處算起約1.2nm。

Complex oxide heterostructures of LaAlO3 (LAO) and SrTiO3 (STO) have drawn a large amount of interest due to its unique physical properties. Many researches have shown that the thickness of LAO should be equal to or greater than the critical value 4 unit cells (u.c.) to make the interface conducting. In other words, the interface of 3u.c. LAO grown on STO is insulating. For application, it is essential to find other methods to control the electronic properties of the interface. With the LAO surface modification by Au nanoclusters, the interfacial two-dimensional electron gas presents a giant optical switching effect under green light illumination. In this study, the results can reveal the evolution of electronic structures in the LAO (3u.c.)/STO model system of the process turning the insulating interface to be conducting by using the technique of cross-sectional scanning tunneling microscopy and spectroscopy. Results clearly reveal the changes in the built-in electric field of the LAO and the band bending in the STO adjacent to the interface with light illumination. The magnitude of the electric field (E) in the LAO is reduced from 23 meVÅ-1 to 9 meVÅ-1. The interfacial band bending (V) at the STO side is 0.39V. The approximate range (λ) at the STO is 1.2 nm.

致謝 i
摘要 ii
Abstract iii
目錄 iv
圖目錄 vi
第一章 緒論 1
1-1 LaAlO3/TiO2-SrTiO3導電介面 1
1-1-1導電介面的發現 1
1-1-2介面電性導電機制 2
1-2 LaAlO3/SrTiO3介面電性控制 3
第二章 研究動機 6
第三章 實驗儀器 7
3-1 掃描穿隧顯微鏡 (Scanning Tunneling Microscopy, STM) 7
3-2 量子穿隧效應 (Quantum tunneling effect) 9
3-3 掃描穿隧能譜 (Scanning Tunneling Spectroscopy, STS) 11
3-4 掃描操作模式 13
3-4-1 定電流模式 14
3-4-2 定高度模式 14
3-4-3 電流影像穿隧能譜 (Current Image Tunneling Spectroscopy, CITS) 15
3-5 超高真空系統 16
3-5-1 真空計 16
3-5-2 真空幫浦 17
3-5-3 烘烤腔體 19
3-5-4 釋氣 19
3-6 掃描探針製備 20
第四章 實驗結果與討論 22
4-1 樣品資訊與實驗方法 22
4-2 實驗結果 23
4-2-1 樣品Au clusters/LaAlO3/SrTiO3異質介面的電性分析 23
4-2-2 樣品pure 3-u.c. LaAlO3/SrTiO3異質介面的電性分析 30
4-3 實驗討論 33
4-3-1表面電漿共振(Surface plasmon resonance, SPR) 33
4-3-2樣品介面的導電機制探討 33
第五章 結論 35
參考文獻 36

[1] A. Ohtomo, D. A. Muller, J. L. Grazul, and H. Y. Hwang, Nature 419, 378 (2002).
[2] Y. Hotta, T. Susaki, and H. Y. Hwang, Physical Review Letters 99, 236805 (2007).
[3] W. A. Harrison, E. A. Kraut, J. R. Waldrop, and R. W. Grant, Physical Review B 18, 4402 (1978).
[4] A. Tsukazaki, A. Ohtomo, T. Kita, Y. Ohno, H. Ohno, and M. Kawasaki, Science 315, 1388 (2007).
[5] G. A. Baraff, J. A. Appelbaum, and D. R. Hamann, Physical Review Letters 38, 237 (1977).
[6] O. Ambacher et al., Journal of Applied Physics 85, 3222 (1999).
[7] A. Ohtomo and H. Y. Hwang, Nature 427, 423 (2004).
[8] S. Okamoto and A. J. Millis, Nature 428, 630 (2004).
[9] J. L. Maurice, C. Carretero, M. J. Casanove, K. Bouzehouane, S. Guyard, E. Larquet, and J. P. Contour, Physica Status Solidi a-Applications and Materials Science 203, 2209 (2006).
[10] M. Basletic et al., Nature Materials 7, 621 (2008).
[11] A. Kalabukhov, R. Gunnarsson, J. Borjesson, E. Olsson, T. Claeson, and D. Winkler, Physical Review B 75, 121404 (2007).
[12] W. Siemons, G. Koster, H. Yamamoto, T. H. Geballe, D. H. A. Blank, and M. R. Beasley, Physical Review B 76, 155111 (2007).
[13] G. Herranz et al., Physical Review Letters 98, 216803 (2007).
[14] J. Lee and A. A. Demkov, Physical Review B 78, 193104 (2008).
[15] W.-j. Son, E. Cho, B. Lee, J. Lee, and S. Han, Physical Review B 79, 245411 (2009).
[16] J. L. Maurice et al., Epl 82, 17003 (2008).
[17] P. R. Willmott et al., Physical Review Letters 99, 155502 (2007).
[18] N. Nakagawa, H. Y. Hwang, and D. A. Muller, Nature Materials 5, 204 (2006).
[19] R. Pentcheva and W. E. Pickett, Physical Review Letters 102, 107602 (2009).
[20] G. Singh-Bhalla, C. Bell, J. Ravichandran, W. Siemons, Y. Hikita, S. Salahuddin, A. F. Hebard, H. Y. Hwang, and R. Ramesh, Nature Physics 7, 80 (2011).
[21] H. Chen, A. Kolpak, and S. Ismail-Beigi, Physical Review B 82, 085430 (2010).
[22] K. Yoshimatsu, R. Yasuhara, H. Kumigashira, and M. Oshima, Physical Review Letters 101, 026802 (2008).
[23] N. C. Bristowe, E. Artacho, and P. B. Littlewood, Physical Review B 80, 045425 (2009).
[24] M. Huijben, G. Rijnders, D. H. A. Blank, S. Bals, S. Van Aert, J. Verbeeck, G. Van Tendeloo, A. Brinkman, and H. Hilgenkamp, Nature Materials 5, 556 (2006).
[25] A. Savoia et al., Physical Review B 80, 075110 (2009).
[26] C. Bell, S. Harashima, Y. Hikita, and H. Y. Hwang, Applied Physics Letters 94, 222111 (2009).
[27] Y. Segal, J. H. Ngai, J. W. Reiner, F. J. Walker, and C. H. Ahn, Physical Review B 80, 241107 (2009).
[28] S. Thiel, G. Hammerl, A. Schmehl, C. W. Schneider, and J. Mannhart, Science 313, 1942 (2006).
[29] W.-J. Son, E. Cho, J. Lee, and S. Han, Journal of Physics-Condensed Matter 22, 315501 (2010).
[30] Y. Xie, Y. Hikita, C. Bell, and H. Y. Hwang, Nature Communications 2, 494 (2011).
[31] K. Au, D. F. Li, N. Y. Chan, and J. Y. Dai, Advanced Materials 24, 2598 (2012).
[32] Y. Li and J. Yu, Journal of Physics-Condensed Matter 25, 265004 (2013).
[33] W. C. Lo, K. Au, N. Y. Chan, H. Huang, C.-H. Lam, and J. Y. Dai, Solid State Communications 169, 46 (2013).
[34] H. Kim, S. Y. Moon, S.-I. Kim, S.-H. Baek, H. W. Jang, and D.-W. Kim, Acs Applied Materials & Interfaces 6, 14037 (2014).
[35] N. Y. Chan, M. Zhao, N. Wang, K. Au, J. Wang, L. W. H. Chan, and J. Dai, Acs Nano 7, 8673 (2013).
[36] T. Vu Thanh et al., Advanced Materials 25, 3357 (2013).
[37] Z. S. Popovic, S. Satpathy, and R. M. Martin, Physical Review Letters 101, 256801 (2008).
[38] K. Janicka, J. P. Velev, and E. Y. Tsymbal, Physical Review Letters 102, 106803 (2009).
[39] B.-C. Huang et al., Physical Review Letters 109, 246807 (2012).
[40] G. Binnig and H. Rohrer, Surface Science 126, 236 (1983).
[41] G. Binnig, H. Rohrer, C. Gerber, and E. Weibel, Physical review letters 49, 57 (1982).
[42] C. J. Chen, Introduction to scanning tunneling microscopy (Oxford University Press, 2008).
[43] D. A. Bonnell, Scanning tunneling microscopy and spectroscopy: theory, techniques, and applications (VCH New York, 1993).
[44] F. Besenbacher, Reports on Progress in Physics 59, 1737 (1996).
[45] E. Taglauer and J. C. Vickerman, (Wiley, New York, 1997).
[46] R. Feenstra, Physical Review B 50, 4561 (1994).
[47] C. Wang and D. Astruc, Chemical Society Reviews 43, 7188 (2014).
[48] P. K. Jain and M. A. El-Sayed, Nano Letters 8, 4347 (2008).
[49] C. Clavero, Nature Photonics 8, 95 (2014).
[50] S. Link and M. A. El-Sayed, Journal of Physical Chemistry B 103, 8410 (1999).
[51] C.-F. Chen, S.-D. Tzeng, H.-Y. Chen, K.-J. Lin, and S. Gwo, Journal of the American Chemical Society 130, 824 (2008).