本論文是利用掃描穿隧式顯微鏡(scanning tunneling microscopy)研究溫度、缺陷和邊界效應對單層鉛原子在矽(111)表面相變化的影響。在第一部分，我們展示了二維系統中尺寸效應(finite-size effects)的量化結果。第二部份是有關於在鉛於矽(111)系統中，區域邊界(domain wall)於相變化所扮演的關鍵角色。第三部份，我們觀察到由於氫原子吸附於表面，進而造成原子重組的新奇結構。

在第一個標題□，在鉛於矽(111)的奈米區域(nano-domain)中我們研究一種可逆的、由溫度誘發的表面結構像變化。在室溫下，單層鉛原子於矽表面呈現出1×1的結構。而當溫度低於270K時，1×1會轉變成√7×√3的結構，而相變化的溫度和區域尺寸有關係。我們的研究顯示當區域尺寸縮小時，相變化溫度也隨之降低。另外，奈米區域的邊界對相變化溫度也是有影響的。在接近相變化溫度時，在√7×√3的結構中常可發現突發的擾動。仔細的檢驗這些快速的擾動行為，我們發現這些擾動和快速區域邊界的移動有關聯。

在第二各標題中，我們研究在鉛於矽(111)系統中，區域邊界(domain wall)於相變化所扮演的重要角色。我們發現了三種基本型態的區域邊界。研究結果顯示，一些邊界和外加的缺陷可以降低形成區域邊界的能量。此外，缺陷也可以在極低溫下，限制區域邊界的移動。而接近相變化溫度時，在區域邊界時常可以首先觀察到擾亂的現象，隨著溫度的升高，擾動地帶也隨之變寬。

第三個標題中，我們探討一個未被發現的新奇的結構。此結構是在室溫的鉛於矽(111)系統中，氫原子吸附於表面引發原子重組所產生的。在氫原子引產生的缺陷週遭，會產生六角形環狀的結構(hexagonal ring-like Pattern)，而其強度會隨著遠離缺陷中心而變弱。此外，在兩個缺陷中心附近可以觀察到一些似六角形環狀的新干涉結構。若兩缺陷中心相距某特定距離，就會產生一個新的、完美的六角形環狀結構。此六角形環狀結構會受到邊界效應的影響，特定的邊界會壓抑也會助長此結構的產生。此結構的產生的原因可能是原子位移和電子結構複雜的交互作用。

The effects of temperatures, defects, and boundaries on the structural transition for monolayer Pb on Si(111) surfaces have been studied with variable-temperature scanning tunneling microscopy (VT-STM). In the first part, we report quantitative measurement of finite-size effects on 2D phase transition. The second part is about the crucial role of domain wall formation in a phase transition of the Pb/Si(111) system. In the third part, we observe a novel atomic rearrangement induced by atomic hydrogen adsorption.

In the first topic, we have studied a reversible, temperature-driven structural surface phase transition of Pb/Si(111) nano-domains. At room temperature, the monolayer Pb exhibits the 1×1 structure. It is transformed into a √7×√3 phase at a temperature below ~ 270 K. The phase transition temperature depends on the domain size. Our measurements indicated that the transition temperature decrease with decreasing domain size. The boundaries of the nano-domains also had effects on the transition. Around the transition temperature, temporal fluctuations could be seen in the structures. Careful examination of the change in the surface structure near the transition temperature revealed the fast dynamics associated with the thermal fluctuations of domain walls.

Second, the important role of domain wall in a two-dimensional (2D) phase transition of the Pb/Si(111) system have been studied. We have found three basic types of domain walls on the surface. The results indicate that certain boundary conditions and addition of point defects can lower the energy for domain wall formation and even pin the domain wall motions at a low enough temperature. The Disordering regions also start from these pinning sites of domain walls. As the temperature is increased, the areas of disordering became broader.

Third, we have observed interesting hydrogen-adsorption induced atomic rearrangements on Pb/Si(111) system at room temperature. A hexagonal ring-like pattern with decaying intensity is formed around the hydrogen-induced point defect. Moreover, interference-like patterns can be seen in the region among the H-induced point defects. With certain relative positions, a new superstructure of hexagonal cells can be seen. The phase boundaries are found to either enhance or suppress the formation of the hexagonal ring-like pattern. We believe that the intricate interplay between atomic displacement and electronic structure causes the formation of the patterns.

Reference

Chapter 1

[1.1] http://www.intel.com/technology/silicon/mooreslaw/
[1.2] J. D. Meindl, Q. Chen, and J. A. Davis, “Limits on silicon nanoelectronics for terascale integration” Science 293, 2044 (2001)
[1.3] M. Schulz, “The end of the road for silicon?” Nature 399, 729 (1999)
[1.4] D. Stiévenard and B. Legrand, Prog. In Surf. Sci. 81, 112 (2006) Silicon surface nano-oxidation using scanning probe microscopy
[1.5] http://www.zyvex.com/nanotech/feynman.html and reference in.
[1.6] Ulrich Gösele, “How clean is too clean” Nature 440, 34 (2006)
[1.7] C. B. Duke, “Surface science 1964-2003” J. Vac. Sci. Technol. A 21, S34 (2003)
[1.8] A. Yoshimori, “Overview of surface science-structures, dynamical processes and microscopies with atomic resolution” Vacuum 65, 223 (2002)
[1.9] G. Binnig, H. Rohrer, Ch. Gerber, E. Weibel, “Surface studied by scanning tunneling miceoscopy” Phys. Rev. Lett. 49, 57 (1982)
[1.10] G. Binnig and H. Rohrer, “In touch with atoms” Rev. Mod. Phys. 71, S324 (1999)
[1.11] Ernst Meyer, Hans Josef Hug, and Roland Bennewitz, Scanning probe microscopy, (Springer, 2003)
[1.12] C. J. Chen, Introduction to scanning tunneling microscopy (Oxford university press, 1993)
[1.13] R. M. Feenstra, A. J. Slavin, G. A. Held, and M. A. Lutz, “Surface diffusion and phase transition on the Ge(111) surface studied by scanning tunneling microscopy” Phys. Rev. Lett. 66, 3257 (1991)
[1.14] D. M. Eigler and E. K. Schweizer, “Positioning single atoms wirh a scanning tunneling microscope” Nature 344, 524(1990)
[1.15] J. Avila, A. Mascaraque, E. G. Michel, M. C. Asensio, G. LeLay, J. Ortega, R. Pérez, and F. Flores “Dynamical Fluctuations as the Origin of a Surface Phase Transition in Sn/Ge(111)” Phys. Rev. Lett. 82, 442 (1999)
[1.16] F. Ronci, S. Colonna, S. D. Thorpe, and A. Cricenti “Direct observation of Sn adatoms dynamical fluctuations at the Sn/Ge(111) surface” Phys. Rev. Lett. 95, 156101 (2005)
[1.17] A. V. Melechko, J. Braun, H. H. Weitering, and E. W. Plummer, “Two-dimensional phase transition mediated by extrinsic defects” Phys. Rev. Lett. 83, 999 (1999)
[1.18] A. V. Melechko, J. Braun, H. H. Weitering, and E. W. Plummer, “Role of defects in two-dimensional phase transitions: An STM study of the Sn/Ge(111) system” Phys. Rev. B 61, 2235 (2000)
[1.19] H. H. Weitering, J. M. Carpinelli, A. V. Melechko, J. Zhang, M. Bartkowiak, and E. W. Plummer, “Defect-mediated condensation of a charge density wave” Science 285, 2107 (1999)
[1.20] S. Stepanovsky, M. Yakes, V. Yeh, M. Hupalo, and M. Tringides, “The dense α-√3×√3Pb/Si(111)phase: A comprehensive STM and SPA-LEED study of ordering, phase transitions and interactions” Surf. Sci. 600, 1417 (2006)
[1.21] C. Kumpf, O. Bunk, Jan H. Zeysing, M. M. Nielsen, M. Nielsen, R. L. Johnson, and R. Feidenhans’l, “Structural study of the commensurate-incommensurate low-temperature phase transition of Pb on Si(111)” Surf. Sci. 448, L213 (2000)
[1.22] O. Custance, J. M. Gómez-Rodríguez, A. M. Baró, L. Juré, P. Mallet, and J. –Y. Veuillen “Low temperature phase of Pb/Si(111)” Surf. Sci. 482-485, 1339 (2001)
[1.23] S. Brochard, E. Artacho, O. Custance, A. M. Baró, I. Brihuega, J. M. Soler, and J. M. Gómez-Rodríguez, “Ab initio calculations and scanning tunneling microscopy experiments of the Si(111)-( √7×√3)” Phys. Rev. B 66, 205403 (2002)
[1.24] J. Slezák, P. Mutombo, and V. Cháb, “STM study of a Pb/Si(111) interface at room temperature and low temperature” Phys. Rev. B 60, 13328 (1999)

Chapter 2

[2.1] K. Takayanagi, Y. Tanishiro, S. Takahashi, and M. Takahashi “Structure analysis of Si(111)-7×7 reconstructed surface by transmission electron diffraction” Surf. Sci. 164, 367 (1985)
[2.2] F. Grey, R. Feidenhans’l, M. Nielsen, and R. L. Johnson ”The relationship between the metastable and stable phases of Pb/Si(111)” J. Phys. Colloq. 50, C7-181 (1989)
[2.3] L. Seehofer, G. Falkenberg, D. Daboul, and R. L. Johnson “Structural study of the close-packed two-dimensional phases of Pb on Ge(111) and Si(111)” Phys. Rev. B 51, 13503 (1995)
[2.4] D. Tang, H. E. Elsayed-Ali, J. Wendelken, and J. Xu “Scanning-tunneling-microscopy study of Pb on Si(111)” Phys. Rev. B 52, 1481 (1995)
[2.5] E. Ganz, F. Xiong, I. S. Hwang, and J. Golovchenko “Submonolayer phases of Pb on Si(111)” Phys. Rev. B 43, 7316 (1991)
[2.6] E. Ganz, I. S. Hwang, F. Xiong, S. K. Theiss, and J. A. Golovchenko “Growth and morphology of Pb on Si(1111)” Surf. Sci. 257, 259 (1991)
[2.7] D. Nakamura, J. Yuhara, and K. Morita “Self-recovery of monolayer Pb adsorbates on the Si(111)-1×1-Pb surface under ion irradiation at room temperature” Surf. Sci. 425, 174 (1999)
[2.8] F. Xiong, E. Ganz, J. A. Golovchenko, and F. Spaepen “In situ RBS and channeling study of molecular beam epitaxial growth of metals and semiconductors on semiconductors” Nucl. Instrum. Methods Phys. Res., Sect. B56/57, 780 (1991)
[2.9] I. S. Hwang, R. Martinez, C. Liu, and J. A. Golovchenko, “Soft incommensurate reconstruction on Pb/Si(111): Structure, stress modulation, and phase transition” Phys. Rev. B 51, 10193 (1995)
[2.10] I. S. Hwang, R. Martinez, C. Liu, and J. A. Golovchenko, “High coverage phases of Pb on the Si(111) surface: structure and phase transitions” Surf. Sci. 323, 241 (1995)
[2.11] J. Slezák, P. Mutombo, and V. Cháb, “STM study of a Pb/Si(111) interface at room temperature and low temperature” Phys. Rev. B 60, 13328 (1999)
[2.12] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Observation of finite-size effects on a structural phase transition of 2D nanoislands” Phys. Rev. Lett. 93, 106101 (2004)
[2.13] O. Custance, I. Brihuega, J. –Y. Veuillen, J. M. Gómez-Rodríguez, and A. M. Baró, “STM study of dynamical effects on submonolayer phases of Pb/Si(111)” Surf. Sci. 482-485, 878 (2001)
[2.14] J. M. Gómez-Rodríguez, J. –Y. Veuillen, and R. C. Cinti, “Scanning tunneling microscopy study of the Si(111)-(√3×√3)-Pb mosaic phase” Surf. Sci. 377-379, 45 (1997)
[2.15] J. Slezák, P. Mutombo, and V. Cháb, “Temperature study of phase coexistence in the system Pb on an Si(111) surface” Surf. Sci. 454-456, 584 (2000)

Chapter 3

[3.1] A. Mascaraque and E. G. Michel, “Reversible structural phase transitions in semiconductor and metal/semiconductor surfaces” J. Phys.: Condens. Matter 14, 6005 (2006)
[3.2] E. Bauer, Structure and Dynamics of Surfaces II, (Springer-Verlag, New York, USA, 1987)
[3.3] V. Privman, Finite Size Scaling and Numerical Simulation of Statistical Systems, (World Scientific, Singapore, 1990)
[3.4] A. N. Goldstein, C. M. Echer, and A. P. Alivisators, “Melting in Semiconductor nanocrystals” Science 256 1425 (1992)
[3.5] I. S. Hwang and J. A. Golovchenko, “Tunneling microscope observation of a structural surface phase transition: Structure, fluctuations, and local effects” Phys.Rev. Lett. 71 255 (1993)
[3.6] I. S. Hwang and J. A. Golovchenko, “Phase transition of monolayer Pb/Ge(111): 1×1 at ~180℃” Phys.Rev. B 50 18535 (1994)
[3.7] Xiao Tong, Kotaro Horikoshi, and Shuji Hasegawa, “Structure and electrical conductance of Pb-covered Si(111) surfaces” Phys. Rev. B 60, 5653 (1999)
[3.8] C. Kumpf, O. Bunk, Jan H. Zeysing, M. M. Nielsen, M. Nielsen, R. L. Johnson, and R. Feidenhans’l, “Structural study of the commensurate-incommensurate low-temperature phase transition of Pb on Si(111)” Surf. Sci. 448, L213 (2000)
[3.9] O. Custance, J. M. Gómez-Rodríguez, A. M. Baró, L. Juré, P. Mallet, and J. –Y. Veuillen “Low temperature phase of Pb/Si(111)” Surf. Sci. 482-485, 1339 (2001)
[3.10] S. Brochard, E. Artacho, O. Custance, A. M. Baró, I. Brihuega, J. M. Soler, and J. M. Gómez-Rodríguez, “Ab initio calculations and scanning tunneling microscopy experiments of the Si(111)-( √7×√3)” Phys. Rev. B 66, 205403 (2002)
[3.11] J. Slezák, P. Mutombo, and V. Cháb, “STM study of a Pb/Si(111) interface at room temperature and low temperature” Phys. Rev. B 60, 13328 (1999)
[3.12] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Observation of finite-size effects on a structural phase transition of 2D nanoislands” Phys. Rev. Lett. 93, 106101 (2004)
[3.13] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Probing dynamics of a phase transition of two-dimensional nano-domains with STM imaging and manipulation” Surf. Sci. 572, L331 (2004)
[3.14] L. D. Landau and E. M. Lifshitz, Statistical Physics, (Addison-Wesley, Reading, MA, 1969)
[3.15] C. C. Hwang, K.-J. Kim, T. -H. Kang, B. Kim, Y. Chung, and C. Y. Park, “Temperature-induced phase transitions of the Si(100) and (113) surfaces” Surf. Sci. 514, 319 (2002)
[3.16] J. Avila, A. Mascaraque, E. G. Michel, M. C. Asensio, G. LeLay, J. Ortega, R. Pérez, and F. Flores, “Dynamical Fluctuations as the Origin of a Surface Phase Transition in Sn/Ge(111)” Phys. Rev. Lett. 82, 442 (1999)
[3.17] F. Ronci, S. Colonna, S. D. Thorpe, and A. Cricenti, “Direct observation of Sn adatoms dynamical fluctuations at the Sn/Ge(111) surface” Phys. Rev. Lett. 95, 156101 (2005)

Chapter 4

[4.1] S. Gangopadhtay, T. Schmidt, and J. Falta, “Influence of substrate domain boundaries on surface reconstructions of Ga/Si(111)” Surf. Sci. 552, 63 (2004)
[4.2] M. J. Rost, S. B. van Albada, and J. W. M. Frenken, “Domain boundary formation on Au(110)” Europhys. Lett. 59, 559 (2002)
[4.3] M. J. Rost, S. B. van Albada, and J. W. M. Frenken, “Thermally activated domain boundary formation on a missing row reconstructed surface: Au(110)” Surf. Sci. 547, 71 (2004)
[4.4] R. E. Reed-Hill, Physical Metallurgy Principles, 3rd ed. (PWS-KENT Publishing Company, Boston, USA, 1992)
[4.5] R. M. Feenstra, A. J. Slavin, G. A. Held, and M. A. Lutz, “Surface diffusion and phase transition on the Ge(111) surface studied by scanning tunneling microscopy” Phys. Rev. Lett. 66, 3257 (1991)
[4.6] H. Hibino and T. Ogino. “Phase transition of 12×1 reconstruction on Si(331)” Surf. Sci. 357-358, 102 (1996)
[4.7] H. Hibino and T. Ogino. “Two-stage phase transition of 12×1 reconstruction on Si(331)” Phys. Rev. B 53, 15682 (1996)
[4.8] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Observation of finite-size effects on a structural phase transition of 2D nanoislands” Phys. Rev. Lett. 93, 106101 (2004)
[4.9] E. Ganz, I. S. Hwang, F. Xiong, S. K. Theiss, and J. A. Golovchenko, “Growth ans morphology of Pb on Si(111)” Surf. Sci. 257, 259 (1991)
[4.10] J. Slezák, P. Mutombo, and V. Cháb, “STM study of a Pb/Si(111) interface at room temperature and low temperature” Phys. Rev. B 60, 13328 (1999)
[4.11] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Observation of finite-size effects on a structural phase transition of 2D nano-domains” Chinese J Phys., 43, 182 (2005)
[4.12] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Hydrogen-adsorption induced atomic rearrangement of a Pb monolayer on Si(111)” Phys. Rev. Lett. 94, 045505 (2005)
[4.13] I. S. Hwang, S. H. Chang, C. K. Fang, L. J. Chen, and T. T. Tsong, “Probing dynamics of a phase transition of two-dimensional nano-domains with STM imaging and manipulation” Surf. Sci. 572, L331 (2004)

Chapter 5

[5.1] David R. Gaskell, Introduction to metallurgical thermodynamics, 2nd ed. (McGraw-Hill, New York, USA, 1981)
[5.2] O. Bikondoa, C. L. Pang, R. Ithnin, C. A. Muryn, H. Onishi, and G. Thornton, “Direct visualization of defect-mediated dissociation of water on TiO2(110)” Nature materials 5, 139 (2006)
[5.3] J. T. Ryu, T. Fuse, O. Kubo, T. Fujino, H. Tani, T. Harada, A. A. Saranin, A. V. Zotov, M. Katayama, and K. Oura, “ Adsorption of atomic hydrogen on the Si(001) 4×3-ln surface stuied by coaxial impact collision ion scattering spectroscopy and scanning tunneling microscopy” J. Vac. Sci. Technol. B 17, 3 (1999)
[5.4] C. -S. Jiang, H. R. Mountinho, M. J. Romero, M. M. Al-Jassim, and L.L. Kazmerski, “Electrical charge trapping at defects on the Si(111) 7×7 surface” Appl. Phys. Lett. 88, 061909 (2006)
[5.5] M. Copel and R. M. Tromp, “H coverage dependence of Si(001) homoepitaxy” Phys. Rev. Lett. 72, 1236 (1994)
[5.6] M. Ishigami, H. J. Choi, S. Aloni, S. G. Louie, M. L. Cohen, and A. Zettl, “Identify defects in nanoscale materials” Phys. Rev. Lett. 93, 196803 (2004)
[5.7] E. Z. da Sliva, A. J. R. da Silva, and A. Fazzio, “How do gold nanowires break?” Phys. Rev. Lett. 87, 256102 (2001)
[5.8] A. V. Melechko, J. Braun, H. H. Weitering, and E. W. Plummer, “Role of defects in two-dimensional phase transitions: An STM study of the Sn/Ge(111) system” Phys. Rev. B 61, 2235 (2000)
[5.9] J. R. Cheng and L. E. Cross, “Effect of La substituent on ferroelectric rohmbohedral/tetragonal morphotropic phase boundary in (1-x)(Bi, La)(Ga0.05Fe0.95)O3-xPbTiO3 piezoelectric ceramics” J. Appl. Phys. 94, 5188 (2003)
[5.10] S. T. Zhang, Y. F. Chen, J. Wang, G. X. Cheng, Z. G. Liu, and N. B. Ming, “Ferroelectric properties of La and Zr substituted Bi4Ti3O12 thin films” Appl. Phys. Lett. 84, 3660 (2004)
[5.11] Y. H. Lee, J. M. Wu, and C. H. Lai, “ Influence of La doping in multiferroic properties of BiFeO3 thin films” Appl. Phys. Lett. 88, 042903 (2006)
[5.12] C. Kittle, Introduction to solid state physics (Wiley, New York, 1976), p. 232
[5.13] M. F. Crommie, C. P. Lutz, and D. M. Eigler, “Imaging standing waves in a two-dimensional electron gas” Nature 363, 524 (1993)
[5.14] M. F. Crommie, C. P. Lutz, and D. M. Eigler, “Confinement of electrons to quantum corrals on a metal surface” Science 262, 218 (1993)
[5.15] J. Repp, F. Mpresco, G. Meyer, K. –H. Rieder, P. Hyldgaad, and M. Persson, “Substrate-mediated long-range oscillatory interaction between adatoms: Cu /Cu(111)” Phys. Rev. Lett. 85, 2981 (2000)
[5.16] F. Sully, M. Pivetta, M. Ternes, F. Patthey, J. P. Pelz, and W. –D. Schneider, “Creation of an atomic superlattice by immersing metallic adatoms in a two-dimensional electron sea” Phys. Rev. Lett. 92, 016101 (2004)
[5.17] H. H. Weitering, J. M. Carpinelli, A. V. Melechko, J. Zhang, M. Bartkowiak, and E. W. Plummer, “Defect-mediated condensation of a charge density wave” Science 285, 2107 (1999)
[5.18] S. S. Lee, J. R. Ahn, N. D. Kim, J. H. Min, C. G. Hwang, J. W. Chung, H. W. Yeom, S. V. Ryjkov, and S. Hasegawa, “Adsorbate-induced pinning of a charge-density wave in a quasi-1D metallic chains: Na on the In/Si(111)-(4×1) surface” Phys. Rev. Lett. 88, 196401 (2002)
[5.19] Y. Kondo, T. Amakusa, M. Iwatsuki, and H. Tokumoto, “phase transition of the Si(001) surface below 100K” Surf. Sci. 453, L318 (2000)
[5.20] R. -L. Lo, I. S. Hwang, M. -S. Ho, and T. T. Tsong, “Diffusion of single hydrogen atoms on Si(111)-(7×7) surfaces” Phys. Rev. Lett. 80 5584 (1998)