本論文中研究及討論所謂的〖(√3×√3)〗_si 矽烯的表面原子結構。〖(√3×√3)〗_si 矽烯是普遍所認知的多層結構的矽烯。實驗的方法利用氘原子吸附於〖(√3×√3)〗_si 矽烯薄膜，並且使用低溫掃描式穿隧顯微鏡 (STM) 觀察改變過後的薄膜。本論文實驗結果為以下：(1)氘原子吸附後形成了一維的氘/矽長鏈狀的結構。氘/矽長鏈結構是隨機以三個銀[101 ̅] 方向排列，且間距為兩倍的矽(111)晶體的晶格常數。(2)某種原子於氘原子吸附於〖(√3×√3)〗_si 矽烯時被驅逐出來並堆積成有特定晶形的島狀結構。經過統計，發現島狀結構彼此間的高度差恰為銀原子層的高度差(0.24 nm)，STS能譜量測於這些島狀結構發現了Coulomb blockade effect週期性的波峰。因此此種原子被確認為銀原子。上述的這兩點特性與Oura等人所研究的氫/(√3×√3)銀-矽(111)系統十分相似，該系統的氫(氘)/矽長鏈結構方向、間隔相同、銀原子也被驅逐出原本的表面形成銀島。我們的實驗結果與先前Shira等人所提出的銀原子置上模型相符。總言之，我們認為所謂〖(√3×√3)〗_si 矽烯實際上是表面覆蓋著銀原子的矽(111)薄膜，而非二維結構的矽烯層狀的堆疊。

This thesis reports and discusses the atomic structure of the (〖√3×√3)〗_si silicene surface. This surface structure is common to all so-called multi-layer silicene film. Our experimental approach is to expose the (〖√3×√3)〗_si silicene film with deuterium atomic beam and to observe the resulting film morphology by low-temperature scanning tunneling spectroscopy (LT-STM). The experiment results reveal that deuterium is absorbed on Si atom to form one-dimension D/Si chains, which are randomly aligned in three of Ag [101 ̅] directions. The separation of these D/Si chains is 2a, where “a” is the lattice constant of Si (111) crystal, 3.84 Å. Some atoms are expelled from (〖√3×√3)〗_si silicene surface and form 3D islands. The height difference of these 3D islands are an integer multiple of Ag (111) step height. The corresponding STS spectra measurement on the islands show the Coulomb blockade effect. Therefore, that atoms forming the 3D islands are verified as Ag. The surface morphology after deuterium adsorption on the “multilayer silicene” is highly similar to that of H/(√3×√3)Ag-Si (111) studied by Oura et al. These findings imply our experiment result is compatible with the Ag-on-top model claimed by Shirai et al.. In summary, we found the so-called multilayer silicene should be rectified as (〖√3×√3)〗_si Si(111)/Ag (111). In the other words, the so-called (〖√3×√3)〗_si silicene is likely an ultra-thin Si (111) film with Ag on its surface.

Abstract - 1 -
摘 要 - 2 -
第一章 簡介 - 5 -
1.1 研究背景與動機 - 5 -
1.2 矽烯(Silicene)各種結構 - 6 -
(4×4)Ag silicene - 7 -
(13×13)Ag silicene - 8 -
(23×23)AgR30° silicene - 10 -
(3×3)Si R30° silicene - 11 -
1.3 相關研究 - 16 -
1.3.1 (3×3)銀/矽(111) - 16 -
1.3.2 氫原子吸附於(3×3)銀/矽(111) - 17 -
1.3.3 Coulomb blockade effects in Ag/Si(111) - 19 -
1.3.4 氫原子吸附於單層的矽烯 - 20 -
1.4 研究計畫 - 22 -
第二章 實驗方法與原理 - 23 -
2.1真空系統 - 23 -
2.1.1真空幫浦及氣壓測量儀介紹 - 24 -
2.1.2抽真空概略程序 - 27 -
2.2 掃描穿隧電子顯微鏡(Scanning Tunneling Microscopy) - 28 -
2.2.1 量子穿隧效應 (Quantum tunneling effect) - 28 -
2.2.2 穿隧式電子顯微鏡細部構造 - 30 -
2.2.3 掃描穿隧式顯微鏡之影像擷取 - 31 -
2.2.4 Scanning tunneling spectroscopy (STS) - 32 -
2.3 蒸鍍源 - 33 -
2.3.1 矽原子蒸鍍槍(Silicon Evaporator) - 33 -
2.3.2 氘分子裂解 (Deuterium cracker) - 33 -
2.4 探針製作與樣品準備 - 34 -
2.4.1 探針製作 - 34 -
2.4.2 (3×3)Si 矽烯成長在銀(111)基板之程序 - 35 -
2.4.3 氘化(3×3)Si矽烯之程序 - 35 -
第三章 實驗結果與討論 - 36 -
3.1 (3×3)Si 矽烯/銀(111)表面結構 - 36 -
3.2 大量氘原子吸附於(3×3)Si矽烯表面 - 39 -
3.2.1 鏈狀之氘/矽結構 - 41 -
3.2.2 銀島 - 43 -
第四章 結論 - 51 -
參考文獻 - 53 -
圖表目錄 - 56 -

1 Vogt, P. et al. Silicene: Compelling Experimental Evidence for Graphenelike Two-Dimensional Silicon. Physical Review Letters 108, 155501 (2012).
2 De Padova, P. et al. Evidence of Dirac fermions in multilayer silicene. Applied Physics Letters 102, 163106, doi:doi:http://dx.doi.org/10.1063/1.4802782 (2013).
3 Paola De, P. et al. The quasiparticle band dispersion in epitaxial multilayer silicene. J. Phys.: Condens. Matter 25, 382202 (2013).
4 Ezawa, M. Valley-Polarized Metals and Quantum Anomalous Hall Effect in Silicene. Physical Review Letters 109, 055502 (2012).
5 Ezawa, M. A topological insulator and helical zero mode in silicene under an inhomogeneous electric field. New Journal of Physics 14, 033003 (2012).
6 Liu, C.-C., Feng, W. & Yao, Y. Quantum Spin Hall Effect in Silicene and Two-Dimensional Germanium. Physical Review Letters 107, 076802 (2011).
7 Lalmi, B. et al. Epitaxial growth of a silicene sheet. Applied Physics Letters 97, 223109, doi:doi:http://dx.doi.org/10.1063/1.3524215 (2010).
8 Feng, B. et al. Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111). Nano Letters 12, 3507-3511, doi:10.1021/nl301047g (2012).
9 Zhi-Long, L. et al. Various atomic structures of monolayer silicene fabricated on Ag(111). New Journal of Physics 16, 075006 (2014).
10 Chiappe, D. et al. Two-Dimensional Si Nanosheets with Local Hexagonal Structure on a MoS2 Surface. Advanced Materials 26, 2096-2101, doi:10.1002/adma.201304783 (2014).
11 Meng, L. et al. Buckled Silicene Formation on Ir(111). Nano Lett. 13, 685-690, doi:10.1021/nl304347w (2013).
12 Tao, L. et al. Silicene field-effect transistors operating at room temperature. Nat Nano 10, 227-231, doi:10.1038/nnano.2014.325
http://www.nature.com/nnano/journal/v10/n3/abs/nnano.2014.325.html#supplementary-information (2015).
13 Guo, Z.-X. & Oshiyama, A. Structural tristability and deep Dirac states in bilayer silicene on Ag(111) surfaces. Physical Review B 89, 155418 (2014).
14 Shirai, T. et al. Structure determination of multilayer silicene grown on Ag(111) films by electron diffraction: Evidence for Ag segregation at the surface. Physical Review B 89, 241403 (2014).
15 Aizawa, H., Tsukada, M., Sato, N. & Hasegawa, S. Asymmetric structure of the Si(111)-3×3-Ag surface. Surface Science 429, L509-L514, doi:http://dx.doi.org/10.1016/S0039-6028(99)00424-0 (1999).
16 Oura, K., Ohnishi, H., Yamamoto, Y., Katayama, I. & Ohba, Y. Atomic‐hydrogen‐induced Ag cluster formation on Si(111)‐√3×√3–Ag surface observed by scanning tunneling microscopy. Journal of Vacuum Science & Technology B 14, 988-991, doi:doi:http://dx.doi.org/10.1116/1.589190 (1996).
17 Lee, G.-W., Chen, H.-D. & Lin, D.-S. Growth mode and structures of silicene on the Ag(111) surface. Applied Surface Science, doi:http://dx.doi.org/10.1016/j.apsusc.2015.01.155.
18 Jamgotchian, H. et al. Growth of silicene layers on Ag(111): unexpected effect of the substrate temperature. J. Phys.: Condens. Matter 24, 172001 (2012).
19 Guo, Z.-X., Furuya, S., Iwata, J.-i. & Oshiyama, A. Absence and presence of Dirac electrons in silicene on substrates. Physical Review B 87, 235435 (2013).
20 Resta, A. et al. Atomic Structures of Silicene Layers Grown on Ag(111): Scanning Tunneling Microscopy and Noncontact Atomic Force Microscopy Observations. Sci. Rep. 3, doi:10.1038/srep02399
http://www.nature.com/srep/2013/130809/srep02399/abs/srep02399.html#supplementary-information (2013).
21 Chun-Liang, L. et al. Structure of Silicene Grown on Ag(111). Applied Physics Express 5, 045802 (2012).
22 Arafune, R., Lin, C. L., Nagao, R., Kawai, M. & Takagi, N. Comment on ``Evidence for Dirac Fermions in a Honeycomb Lattice Based on Silicon''. Physical Review Letters 110, 229701 (2013).
23 Chen, L. et al. Evidence for Dirac Fermions in a Honeycomb Lattice Based on Silicon. Phys. Rev. Lett. 109, 056804 (2012).
24 Mannix, A. J., Kiraly, B., Fisher, B. L., Hersam, M. C. & Guisinger, N. P. Silicon Growth at the Two-Dimensional Limit on Ag(111). ACS Nano 8, 7538-7547, doi:10.1021/nn503000w (2014).
25 Oura, K., Lifshits, V. G., Saranin, A. A., Zotov, A. V. & Katayama, M. Hydrogen interaction with clean and modified silicon surfaces. Surf. Sci. Rep. 35, 1-69, doi:Doi: 10.1016/s0167-5729(99)00005-9 (1999).
26 Schmeidel, J., Pfnür, H. & Tegenkamp, C. Coulomb blockade effects in Ag/Si(111): The role of the wetting layer. Physical Review B 80, 115304 (2009).
27 Qiu, J. et al. Ordered and Reversible Hydrogenation of Silicene. Physical Review Letters 114, 126101 (2015).
28 Salomon, E., Ajjouri, R. E., Lay, G. L. & Angot, T. Growth and structural properties of silicene at multilayer coverage. Journal of Physics: Condensed Matter 26, 185003 (2014).
29 Voigtländer, B., Zinner, A., Weber, T. & Bonzel, H. P. Modification of growth kinetics in surfactant-mediated epitaxy. Physical Review B 51, 7583-7591 (1995).
30 Altsinger, R., Busch, H., Horn, M. & Henzler, M. Nucleation and growth during molecular beam epitaxy (MBE) of Si on Si(111). Surface Science 200, 235-246, doi:http://dx.doi.org/10.1016/0039-6028(88)90524-9 (1988).
31 Horn-von Hoegen, M., LeGoues, F. K., Copel, M., Reuter, M. C. & Tromp, R. M. Defect self-annihilation in surfactant-mediated epitaxial growth. Physical Review Letters 67, 1130-1133 (1991).
32 Meyer, G., Voigtländer, B. & Amer, N. M. Scanning tunneling microscopy of surfactant-mediated epitaxy of Ge on Si(111): strain relief mechanisms and growth kinetics. Surface Science 274, L541-L545, doi:http://dx.doi.org/10.1016/0039-6028(92)90519-C (1992).
33 Voigtländer, B. & Zinner, A. Influence of surfactants on the growth-kinetics of Si on Si(111). Surface Science Letters 292, L775-L780, doi:http://dx.doi.org/10.1016/0167-2584(93)90833-5 (1993).
33 arXiv:1405.7534 http://arxiv.org/abs/1405.7534.