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研究生:蔡松庭
研究生(外文):Tsai, Sun-Ting
論文名稱:類拓樸絕緣體之合金薄膜的自旋、電子與晶格結構研究
論文名稱(外文):Study of spin, electronic, and lattice structures of a Quasi-Topological-Insulator allsy thin film
指導教授:唐述中
指導教授(外文):Tang, Shu-Jung
學位類別:碩士
校院名稱:國立清華大學
系所名稱:物理系
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2013
畢業學年度:101
語文別:中文
論文頁數:39
中文關鍵詞:拓樸絕緣體合金薄膜迪拉克錐
外文關鍵詞:Topological InsulatorAlloyThin filmDirac cone
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  • 收藏至我的研究室書目清單書目收藏:0
過去的研究中發現鉛(1×1)薄膜在低溫時可以以單一晶域(Domain)平整成長在金/鍺(111)-(√3×√3)R30°的表面上,在這個研究中更進一步利用退火(Anneal)到室溫的方法,使潤濕層(Wetting Layer)中部分的金與鉛薄膜鍵結,在表面形成鉛金合金薄膜。
藉由改變光能量,我們區別了這個材料角解析光電子能譜(Angle-resolved Photoemission Spectrum, ARPES)中能帶的表面或塊材的特性。等能量面成像(Constant Energy Mapping)測量也使我們了解合金薄膜的表面態與基底、潤濕層、鉛薄膜、合金薄膜自身表面結構間的關係。
ARPES顯示合金薄膜的表面態表現出線性的色散關係,一般被稱為迪拉克錐(Dirac Cone)。材料能帶結構中的迪拉克錐在近年的許多研究中都顯示會有自旋結構,自旋解析光電子能譜(Spin-resolved Photoemission Spectrum, SRPES)也證實了這個薄膜的表面態在能帶結構表現出獨特的自旋與動量的相關性。
在這篇論文中我們也提出了室溫下摻雜金來更穩定有效率製備這個鉛金合金薄膜的方法。藉由一點一點摻雜少量的金,我們可以研究鉛金合金薄膜的成長過程。在成長過程中,ARPES的不同表面態消長以及低能量電子繞射(Low Energy Electron Diffraction, LEED)圖形的繞射亮點強度變化,提供了求解鉛金合金的結構中鉛、金比例的方法。

The previous research shows that the thin film of Pb(1×1) structure could be stable in only single domain on the surface of the Au/Ge(111)- (√3×√3)R30° wetting layer at low temperature. In this research, we further make Pb atoms of the thin film bond with some of the Au atoms of the wetting layer, to form an alloy thin film on the surface of the Pb thin film by annealing it to room temperature.
With different photon energies, we distinguish the surface between bulk nature of the energy bands of this material by using angle-resolved photoemission spectroscopy (ARPES). Measuring constant energy contours, we can also realize the characters of the electronic states of the 2D alloy films.
Our measurement shows that the alloy thin film exhibits unique electronic structure of linear dispersion relation, which we usually call Dirac cone. The band structures of Dirac cones possess particular spin textures, which locks the spin polarization in the direction perpendicular to momentum. By using spin-resolved photoemission spectroscopy, we confirm that the electron states of Dirac cones of this alloy display particular chirality of their direction of spin and momentum.
In this thesis, we also propose an alternative method to prepare this alloy thin film by doping Au atoms to the Pb films annealed to room temperature. This method is not only more stable but also more effective. Doping of the Au atoms little by little, we can study the formation of the alloy thin film. In this process, the intensities of the surface states measured by ARPES as well as the diffraction spots measured by the low energy electron diffraction would correspondingly change, providing a way to know the ratio of Au to Pb atoms for this alloy film.

目錄
中文摘要……………………………………………………………………………….i
英文摘要……………………………………………………………………………...iii
目錄……………………………………………………………………………………v
第一章 引論…………………………………………………………………………1
1.1 動機……………………………………………………………………………….1
1.2 工作……………………………………………………………………………….2
1.3 結構……………………………………………………………………………….2
第二章 基礎理論…………………………………………………………...............3
2.1 二維系統………………………………………………………………………….3
2.2 表面……………………………………………………………………………….3
2.3 表面態…………………………………………………………………………….4
2.4 自旋軌道耦合…………………………………………………………………….5
2.5 迪拉克錐………………………………………………………………………….7
第三章 實驗儀器……………………………………………………………………9
3.1 實驗環境-超高真空UHV………………………………………………………..9
3.1.1 目的………………………………………………………………………..9
3.1.2 方法………………………………………………………………………..9
3.2 低能量電子繞射………………………………………………………………...11
3.2.1 布拉格繞射………………………………………………………………11
3.2.2 勞厄方程式………………………………………………………………11
3.2.3 低能量電子繞射…………………………………………………………11
3.2.4 愛華德球…………………………………………………………………12
3.3 角解析光電子能譜儀…………………………………………………………...15
3.3.1 光電效應…………………………………………………………………15
3.3.2 能量分佈曲線(EDC)…………………………………………………16
3.3.3 角解析與動量守恆………………………………………………………17
3.3.4 能量分析儀………………………………………………………………18
3.4 自旋解析光電子能譜儀………………………………………………………...19
第四章 樣品製備…………………………………………………………………..21
4.1 乾淨Ge(111)製備…………………………………………………..…………..21
4.1.1 振洗………………………………………………………………………21
4.1.2 濺射和退火………………………………………………………………21
4.1.3表面乾淨程度確認……………………………………………………….21
4.1.4表面重構確認…………………………………………………………….22
4.2 潤濕層製備……………………………………………………………………...22
4.3 鉛薄膜成長……………………………………………………………………...22
4.4 自然回溫至室溫………………………………………………………………...22
4.5 潤濕層對自然回溫製備合金的影響…………………………………………...23
4.5.1 退火溫度…………………………………………………………………23
4.5.2 厚度………………………………………………………………………23
第五章 實驗分析…………………………………………………………………..25
5.1 合金形成過程…………………………………………………………………..25
5.2 迪拉克錐………………………………………………………………………..29
5.2.1 線性色散關係……………………………………………………………29
5.2.2 不同光能量的ARPES能譜…………………………………………….31
5.2.3 等能量面…………………………………………………………………32
5.2.4 自旋結構…………………………………………………………………34
5.2.5 理論計算…………………………………………………………………36
第六章 結論………………………………………………………………………..37

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[2] Koroteev, Y. M., et al. “Strong spin-orbit splitting on Bi surfaces.”, Physical review letters 93, 046403(2004).
[3] Fu, Liang; C. L. Kane. “Topological insulators with inversion symmetry”, Phys. Rev. B 76, 045302 (2007)
[4] D. Hsieh, et al. “A topological Dirac insulator in a quantum spin Hall phase” Nature 452, 970–974 (2008)
[5] Hans Lüth. Solid Surfaces, Interfaces and Thin Films, Springer (2001)
[6] Neil W. Ashcroft; N. David Mermin. Solid State Physics. Saunders College (1976)
[7] Bercioux, Dario. "Spin-orbit interactions in semiconductor nanostructures."
[8] Avouris, P., Chen, Z., & Perebeinos, V. “Carbon-based electronics.” Nature nanotechnology, 2(10), 605-615 (2007).
[9] Lin, H., Bansil, A., & Fu, L. “Viewpoint: Warping the cone on a Topological Insulator.” Physical Review Letters 103, 266801(2009).
[10]Stefan Hüfner. Photoelectron Spectroscopy, Springer.
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[13]User Mannual SCIENTA R3000, VG SCIENTA.
[14] Taichi Okuda, et al. “Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center”, Review of Scientific Instrument 79(123117), 2008.
[15] Y. L. Chen, et al. “Experimental Realization of a Three-Dimensional Topological Insulator, Bi2Te3”, Science 325(1173034), 178, 2009.
[16] Liang Fu, “Hexagonal Warping Effect in the Surface States of the Topological Insulator Bi2Te3”, Physical Review Letters 103(266801), 2009.

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