本論文以低能量電子繞射(LEED)與角解析光電子能譜(ARPES)來研究在銀上各種覆蓋率的鍺烯上的單原子鉛層的晶格與電子結構，即厚QP、標準QP以及薄QP。
從相應的LEED圖可以看出，這三種情況下的單原子鉛層的晶格結構完全不同。由於我們在LEED圖中觀察不到鍺烯的LEED點，因此我認為鉛層與QP鍺烯是完全相稱的，但是QP鍺烯相對於底下的銀(111)有進一步的旋轉，藉由觀察QP鍺烯與銀(111)之間的重合晶格匹配(CLM)，我們可以使用一種方法來計算CLM密度與鉛層和QP鍺烯的晶格應變，以及QP鍺烯與銀(111)之間的旋轉角度。
以下是可以最吻合地模擬三種情況的LEED圖的結果:
厚QP上的鉛重合密度:0.0092、鉛應變: 3.402%和QP應變: 0.134%，鉛層相對於銀(111)的旋轉角度:4.715°。標準QP上的鉛重合密度:0.0080、鉛應變: 1.970%和QP應變:1.329%，鉛層相對於銀(111)的旋轉角度:10.158°。而薄QP情況則有六種組合，鉛重合度:0.0058~0.0192、鉛應變:0.05%~2.34%和QP應變: 0.87%~3.43%，鉛層相對於銀(111)的旋轉角度:8.080°~10.787°。
而對於鉛/薄QP/銀(111)，我們進一步研究了能帶結構，它與單層鉛在銀(111)上的能帶結構較為類似，通過與DFT計算的獨立存在的單原子鉛層的能帶進行比較後，我們觀察到在表面區域中心的Pz能帶消失了，這歸因於鉛層與銀(111)之間的交互作用。
在沉積更多鍺在鉛/薄QP/銀(111)上，並退火至240 °C後，我們發現Pz能帶出現了，這表示最上層額外的鍺原子沉到薄QP鍺烯之中，進而降低了上層的鉛層與底層的銀(111)之間的交互作用。

In this thesis, the techniques of low-energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES) were used to study the lattice and electronic structures of monatomic Pb layer grown on top of germanene of various coverage on Ag(111), namely, thicker QP, standard QP, and thinner QP. .
The lattice structures of monatomic Pb layers for these three cases are different, as revealed from the corresponding LEED patterns. Because the LEED spots from germanene are absent, I consider the Pb layer to be fully commensurate with QP germanene that can however further rotates from the original direction with respect to the underlying Ag(111). By considering the coincident lattice match (CLM) between QP germanene and Ag(111), we use an algorithm to compute the density of CLM versus lattice strains of Pb layer and QP germanene along with a rotation angle between QP germanene and Ag(111). The results derived that can best simulate LEED patterns for the three cases are the following; for thicker QP, denstiy 0.0092, Pb strain 3.402% and QP strain 0.134% with 4.715°; for standard QP, density 0.0080, Pb strain 1.970% and QP strain 1.329% with 10.158°. However for thinner QP, there are six combinations. The corresponding density varies 0.0058 ~ 0.0192, Pb strain 2.34% ~ 0.05% and QP strain 0.87% ~ 3.43% with 8.080°~10.787°.
For the case of Pb/thinner QP/Ag (111), we further investigate the energy band structures, which appear similar to that of monatomic Pb layer on Ag (111). Upon comparison with DFT calculated energy bands of one-layer freestanding Pb(111), we observe that the pz energy band centered at the surface zone center is missing. This was ascribed to the electron-electron interaction between the Pb layer and Ag(111). After depositing extra Ge atoms onto Pb/thinner QP/Ag (111) followed by annealing to 240 °C, we find the pz band appeared, indicating that the extra Ge atoms sink into QP germanene reducing the interaction between the top Pb layer and the bottom Ag(111).

[1] N. G. Szwacki, and T. Szwacka, Basic Elements of Crystallography, Pan Stanford (2010)
[2] D. Knebl, Shockley surface states from first principles, Master’s thesis, University of Graz (2013)
[3] 蘇青森。真空技術精華。臺北市：五南。ISBN 978-957-11-3478-9 (2003)
[4] H. Lüth, Surface and interface of solids Materials, 3rd edition, Springer (2001)
[5] S. H¨ufner, Photoelectron Spectroscopy, Springer (2003)
[6] User Manual SCIENTA R3000, VG SCIENTA
[7] HIS 13 VUV Lamp Manual
[8] C. H. Lin, A. Huang, W. W. Pai, W. C. Chen, T. Y. Chen, T. R. Chang, R. Yukawa, C. M. Cheng, C. Y. Mou, I. Matsuda, T. C. Chiang, H. T. Jeng, and S. J. Tang, Single-layer dual germanene phases on Ag(111), Phys. Rev. Mater. 2, 024003 (2018)
[9] G. Bihlmayer, J. Sassmannshausen, A. Kubetzka, S. Blügel, K. V. Bergmann, and R. Wiesendanger, Plumbene on a Magnetic Substrate: A Combined Scanning Tunneling Microscopy and Density Functional Theory Study, Phys. Rev. Lett. 124, 126401 (2020)
[10] T. Zhang, P. Cheng, W. J. Li, Y. J. Sun, G. Wang, X. G. Zhu, K. He, L. Wang, X. MA, X. Chen, Y. Wang, Y. Liu, H. Q. Lin, J. F. Jia, and Q. K. Xue, Superconductivity in one-atomic-layer metal films grown on Si(111),
Nat. Phys. 6, 104 (2010)
[11] T.-Y. Chen, Triggering the formation of quasi-freestanding germanene by foreign-atoms deposition, Master’s thesis, University of National Tsing Hua (2018)
[12] S. Chiniwar, A. Huang, T. Y. Chen, C. H. Lin, C. R. Hsing, W. C. Chen, C. M. Cheng, H. T. Jeng, C. M. Wei, W. W. Pai, and S. J. Tang, Substrate-mediated umklapp scattering at the incommensurate interface of a monatomic alloy layer. Phys. Rev. B 99, 155408 (2019)
[13] I. I. Naumov and P. Dev, Quantum materials interfaces: Graphene/bismuth (111) heterostructures, Phys. Rev. Res. 2, 023157 (2020)