這篇論文主旨在探討鐵電及多鐵性複合氧化物薄膜在應變操控下的物理特性變化，主要針對在鋯鈦酸鉛 (PbZr0.2Ti0.8O3, PZT)、鋯鉿氧化物 (Hf0.5Zr0.5O2, HZO) 以及鐵酸鉍 (BiFeO3, BFO) 系統進行操控。本研究探索了三種控制鐵電性的方法：PZT中的外延應變調控、應用於HZO的自支撐獨立式薄膜製程，以及結合外延技術與自支撐獨立式薄膜技術的BFO自支撐獨立式輔助的應變調控。這些策略旨在發掘新的可能性，並加深對鐵電性質如何通過與晶格結構耦合而改變的理解。另外，利用自支撐獨立式薄膜製程，有望解決與以矽為主體的半導體元件的相容性問題，同時增強鐵電材料的功能性質。
在PZT的研究中，分析了(101)晶向的PZT薄膜中超疇域 (superdomain) 的結構細節及鐵電域性質。研究結果顯示，由於鐵彈性疇域轉換，超疇域配置表現出多態切換行為，並顯著提升了壓電響應。超疇域與傳統P1/P2疇域之間的可逆轉換，為先進的電子設備，特別是非揮發性記憶體應用，提供了有希望的發展途徑。對於HZO，採用了自由支撐技術來製作無應變的HZO膜，以解決與其他系統的相容性問題。為了優化功能表現，研究了鐵電薄膜中與厚度相關的行為。研究發現隨厚度增加HZO的正交晶節後會逐漸被單斜晶結構取代，而鐵電極化會因此而減弱。此外，實驗結果還突顯了HZO在介電和絕緣性質方面的提升，進一步證明了其作為場效應電晶體中介電柵層的潛力。為了持續調整應變狀態，將多鐵性BFO薄膜生長於特定的自由支撐式薄膜基板上，並展現了有趣的應變依賴行為。在自支撐獨立式的鈦酸鍶 (freestanding SrTiO3, FS-STO) 緩衝層厚度在20~40 nm之間觀察到最大的應變，這顯著影響了疇域尺寸和反鐵磁性的耦合行為。BFO中應變與疇域結構的相互作用，為未來應用中調控其多鐵性質開闢了新的可能性。
通過使用所提出的方法控制應變狀態，本研究提供了應變、疇域結構與鐵電及多鐵性質之間基本相互作用的更深入理解。對於相變、疇域轉換機制及材料性質優化的洞見，不僅增進了對鐵電及多鐵性材料的了解，也拓展了對複雜性氧化物系統中透過應變所引發的現象的理解，為材料科學與凝態物理領域的研究開闢了新途徑。

This thesis focuses on strain manipulation in ferroelectric and multiferroic complex oxide thin films, with an emphasis on lead zirconate titanate (PbZr0.2Ti0.8O3, PZT), hafnium zirconate (Hf0.5Zr0.5O2, HZO), and bismuth ferrite (BiFeO3, BFO) systems. The research explores three primary approaches for controlling ferroelectricity: epitaxial strain tuning in PZT, the freestanding method applied to HZO, and freestanding-assisted strain tuning, which combines epitaxy and the freestanding technique, in BFO. These strategies aim to uncover novel possibilities and deepen the understanding of how ferroelectric properties are altered through coupling with lattice structure. The freestanding method, in particular, is expected to address compatibility challenges with semiconductor devices, especially silicon-based platforms, while enhancing the functional properties of ferroelectric materials.
In the case of PZT, the study analyzes the structural details and ferroelectric domain properties of superdomains in (101)-oriented PZT thin films. The findings reveal multistate switching behavior and a significantly enhanced piezoelectric response in superdomain configurations, attributed to ferroelastic domain transitions. The reversible switch between superdomain and conventional P1/P2-domains presents a promising avenue for advanced electronic devices, particularly in non-volatile memory applications. For HZO, the freestanding technique is employed to create strain-free HZO membranes for addressing compatibility issues with other systems. To optimize functional performance, thickness-dependent behavior in ferroelectric thin films is explored. The study identifies a critical threshold where ferroelectric polarization is suppressed due to a phase transition from orthorhombic to monoclinic as thickness increases. Additionally, the results highlight enhanced dielectric and insulation properties in HZO and further demonstrate its potential as a dielectric gate layer in field-effect transistors. To continuously tune the strain state, multiferroic BFO thin films are grown on specific freestanding substrates, revealing interesting strain-dependent behavior. Maximum strain is observed at intermediate buffer layer freestanding SrTiO3 (FS-STO) thicknesses, which significantly influences domain size and antiferromagnetic coupling. This interplay between strain and domain configuration in BFO opens up new possibilities for tuning its multiferroic properties in future applications.
By controlling strain states using the proposed methods, this work provides a deeper understanding of the fundamental interplay between strain, domain structure, and ferroelectric/multiferroic behavior. The insights gained into phase transitions, domain switching mechanisms, and material property optimization contribute to advancing the physics of ferroelectric and multiferroic materials. This knowledge not only enhances their potential for technological applications but also broadens the understanding of strain-mediated phenomena in complex oxide systems, opening new avenues for future studies in material science and condensed matter physics.

1 N. Mott, On metal-insulator transitions, Journal of Solid State Chemistry 88, 5-7 (1990).
2 T. Kimura et al., Magnetic control of ferroelectric polarization, Nature 426, 55-58 (2003).
3 T. Zhao et al., Electrical control of antiferromagnetic domains in multiferroic BiFeO3 films at room temperature, Nature materials 5, 823-829 (2006).
4 D. D. Fong et al., Ferroelectricity in ultrathin perovskite films, Science 304, 1650-1653 (2004).
5 T. Tybell, C. Ahn & J.-M. Triscone, Ferroelectricity in thin perovskite films, Applied physics letters 75, 856-858 (1999).
6 R. E. Cohen, Origin of ferroelectricity in perovskite oxides, Nature 358, 136-138 (1992).
7 T. Atou, H. Chiba, K. Ohoyama, Y. Yamaguchi & Y. Syono, Structure determination of ferromagnetic perovskite BiMnO3, Journal of Solid State Chemistry 145, 639-642 (1999).
8 C. Zener, Interaction between the d-shells in the transition metals. II. Ferromagnetic compounds of manganese with perovskite structure, Physical Review 82, 403 (1951).
9 G. Jonker & J. Van Santen, Ferromagnetic compounds of manganese with perovskite structure, Physica 16, 337-349 (1950).
10 P. Yu et al., Interface Ferromagnetism and Orbital Reconstruction in BiFeO3-La0.7Sr0.3MnO3 Heterostructures, Physical Review Letters 105, 027201 (2010).
11 H. Röder, J. Zang & A. R. Bishop, Lattice Effects in the Colossal-Magnetoresistance Manganites, Physical Review Letters 76, 1356-1359 (1996).
12 S. Jin, M. McCormack, T. Tiefel & R. Ramesh, Colossal magnetoresistance in La-Ca-Mn-O ferromagnetic thin films, Journal of Applied Physics 76, 6929-6933 (1994).
13 M. Uehara, S. Mori, C. Chen & S.-W. Cheong, Percolative phase separation underlies colossal magnetoresistance in mixed-valent manganites, Nature 399, 560-563 (1999).
14 R. Liang et al., Growth and properties of superconducting YBCO single crystals, Physica C: Superconductivity 195, 51-58 (1992).
15 D. A. Wollman, D. J. Van Harlingen, W. C. Lee, D. M. Ginsberg & A. J. Leggett, Experimental determination of the superconducting pairing state in YBCO from the phase coherence of YBCO-Pb dc SQUIDs, Physical Review Letters 71, 2134-2137 (1993).
16 E. Morosan, D. Natelson, A. H. Nevidomskyy & Q. Si, Strongly correlated materials, Advanced Materials 24, 4896-4923 (2012).
17 N. F. Mott, Metal-Insulator Transition, Reviews of Modern Physics 40, 677-683 (1968).
18 J. Zaanen, G. A. Sawatzky & J. W. Allen, Band gaps and electronic structure of transition-metal compounds, Physical Review Letters 55, 418-421 (1985).
19 N. F. Mott, The Basis of the Electron Theory of Metals, with Special Reference to the Transition Metals, Proceedings of the Physical Society. Section A 62, 416 (1949).
20 J. Hubbard & B. H. Flowers, Electron correlations in narrow energy bands, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 276, 238-257 (1963).
21 Z. Nussinov & J. van den Brink, Compass models: Theory and physical motivations, Reviews of Modern Physics 87, 1-59 (2015).
22 W.-B. Wu & D.-J. Huang. Orbital Polarization and Electron Correlation of Manganese and Cobalt Oxides, Ph.D. thesis, National Chiao Tung University, (2005).
23 R. Schmidt, E. Langenberg, J. Ventura & M. Varela, Bi containing multiferroic perovskite oxide thin films, arXiv preprint arXiv:1402.1442 (2014).
24 M. Opel, Spintronic oxides grown by laser-MBE, Journal of Physics D: Applied Physics 45, 033001 (2012).
25 Y.-D. Liou et al., Deterministic optical control of room temperature multiferroicity in BiFeO3 thin films, Nature Materials 18, 580-587 (2019).
26 A. Ohtomo & H. Y. Hwang, A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface, Nature 427, 423-426 (2004).
27 N. Nakagawa, H. Y. Hwang & D. A. Muller, Why some interfaces cannot be sharp, Nature materials 5, 204-209 (2006).
28 A. Brinkman et al., Magnetic effects at the interface between non-magnetic oxides, Nature Materials 6, 493-496 (2007).
29 Y. Zhang et al., Strain-driven Dzyaloshinskii-Moriya interaction for room-temperature magnetic skyrmions, Physical Review Letters 127, 117204 (2021).
30 M. Fiebig, T. Lottermoser, D. Meier & M. Trassin, The evolution of multiferroics, Nature Reviews Materials 1, 16046 (2016).
31 S. Fedulov. in Doklady Akademii Nauk. 1345-1346 (Russian Academy of Sciences).
32 J. F. Ihlefeld et al., Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations, Journal of the American Ceramic Society 99, 2537-2557 (2016).
33 J. Wang et al., Ferroelectric domain-wall logic units, Nature Communications 13, 3255 (2022).
34 M. P. F. Graça & M. A. Valente, Ferroelectric glass-ceramics, MRS Bulletin 42, 213-219 (2017).
35 D. Dragan, Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics, Reports on Progress in Physics 61, 1267 (1998).
36 C. A. Randall, Z. Fan, I. Reaney, L. Q. Chen & S. Trolier‐McKinstry, Antiferroelectrics: History, fundamentals, crystal chemistry, crystal structures, size effects, and applications, Journal of the American Ceramic Society 104, 3775-3810 (2021).
37 C. Krowne, Physics of ferroelectric differential capacitance based upon free energy, and implications for use in electronic devices, Journal of Advanced Dielectrics 9, 1950002 (2019).
38 M. E. Lines & A. M. Glass. Principles and applications of ferroelectrics and related materials. (Oxford university press, 2001).
39 S. Wang. Phase-Field Modeling of Relaxor Ferroelectrics and Related Composites, PhD thesis, Technische Universität Darmstadt, (2019).
40 M. Hoffmann et al., Unveiling the double-well energy landscape in a ferroelectric layer, Nature 565, 464-467 (2019).
41 S. R. Bakaul et al., Single crystal functional oxides on silicon, Nature communications 7, 10547 (2016).
42 S. S. Cheema et al., Ultrathin ferroic HfO2–ZrO2 superlattice gate stack for advanced transistors, Nature 604, 65-71 (2022).
43 Y. Wang et al., Epitaxial ferroelectric Pb(Zr, Ti)O3 thin films on Si using SrTiO3 template layers, Applied Physics Letters 80, 97-99 (2002).
44 M. Kelly et al., Optical patterning of GaN films, Applied physics letters 69, 1749-1751 (1996).
45 W. Wong, T. Sands & N. Cheung, Damage-free separation of GaN thin films from sapphire substrates, Applied Physics Letters 72, 599-601 (1998).
46 Q. Gan, R. Rao, C. Eom, J. Garrett & M. Lee, Direct measurement of strain effects on magnetic and electrical properties of epitaxial SrRuO3 thin films, Applied Physics Letters 72, 978-980 (1998).
47 D. Lu et al., Synthesis of freestanding single-crystal perovskite films and heterostructures by etching of sacrificial water-soluble layers, Nature Materials 15, 1255-1260 (2016).
48 J. Kim et al., Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene, Nature communications 5, 4836 (2014).
49 C.-F. Chu et al., Study of GaN light-emitting diodes fabricated by laser lift-off technique, Journal of Applied Physics 95, 3916-3922 (2004).
50 L. Dai, F. An, J. Zou, X. Zhong & G. Zhong, Freestanding inorganic oxide films for flexible electronics, Journal of Applied Physics 132 (2022).
51 D. Ji et al., Freestanding crystalline oxide perovskites down to the monolayer limit, Nature 570, 87-90 (2019).
52 C.-C. Chiu et al., Presence of Delocalized Ti 3d Electrons in Ultrathin Single-Crystal SrTiO3, Nano Letters 22, 1580-1586 (2022).
53 S. S. Hong et al., Two-dimensional limit of crystalline order in perovskite membrane films, Science Advances 3, eaao5173 (2017).
54 B. Peng et al., Phase transition enhanced superior elasticity in freestanding single-crystalline multiferroic BiFeO3 membranes, Science Advances 6, eaba5847 (2020).
55 G. Dong et al., Super-elastic ferroelectric single-crystal membrane with continuous electric dipole rotation, Science 366, 475-479 (2019).
56 C. Jin et al., Super-Flexible Freestanding BiMnO3 Membranes with Stable Ferroelectricity and Ferromagnetism, Advanced Science 8, 2102178 (2021).
57 M. Altmeyer et al., Magnetism, spin texture, and in-gap states: atomic specialization at the surface of oxygen-deficient SrTiO3, Physical review letters 116, 157203 (2016).
58 J.-K. Huang et al., High-κ perovskite membranes as insulators for two-dimensional transistors, Nature 605, 262-267 (2022).
59 Y. Y. Illarionov et al., Insulators for 2D nanoelectronics: the gap to bridge, Nature communications 11, 3385 (2020).
60 P.-C. Wu et al., Twisted oxide lateral homostructures with conjunction tunability, Nature Communications 13, 2565 (2022).
61 D. R. NORTON, Pulsed Laser Deposition of Complex Materials: Progress, Pulsed laser deposition of thin films: applications-led growth of functional materials, 1 (2007).
62 H.-U. Krebs et al., Pulsed laser deposition (PLD)--a versatile thin film technique, Advances in solid state physics, 505-518 (2003).
63 D. H. Lowndes, D. B. Geohegan, A. A. Puretzky, D. P. Norton & C. M. Rouleau, Synthesis of Novel Thin-Film Materials by Pulsed Laser Deposition, Science 273, 898-903 (1996).
64 Y. Waseda, E. Matsubara & K. Shinoda. in X-Ray Diffraction Crystallography: Introduction, Examples and Solved Problems (eds Y. Waseda, E. Matsubara, & K. Shinoda) 67-106 (Springer Berlin Heidelberg, 2011).
65 N. Hua. Nanoscale Studies of Strongly Correlated Electron Materials with Coherent X-Rays. (University of California, San Diego, 2020).
66 C. Kittel & P. McEuen. Introduction to solid state physics. (John Wiley & Sons, 2018).
67 U. Pietsch, V. Holý & T. Baumbach. in High-Resolution X-Ray Scattering: From Thin Films to Lateral Nanostructures (eds U. Pietsch, V. Holý, & T. Baumbach) 43-58 (Springer New York, 2004).
68 P. Willmott. in An Introduction to Synchrotron Radiation 19-49 (2019).
69 D. F. Swinehart, The beer-lambert law, Journal of chemical education 39, 333 (1962).
70 C.-Y. Kuo. Spin orientation in multiferroic thin films of BiFeO3: a polarized soft X-ray absorption study, Technische Universität Dresden, (2017).
71 B. Thole et al., 3d x-ray-absorption lines and the 3d94fn+1 multiplets of the lanthanides, Physical Review B 32, 5107 (1985).
72 J.-M. Chen et al., A complete high-to-low spin state transition of trivalent cobalt ion in octahedral symmetry in SrCo0.5Ru0.5O3-δ, Journal of the American Chemical Society 136, 1514-1519 (2014).
73 Z. Hu et al., Different look at the spin state of Co3+ ions in a CoO5 pyramidal coordination, Physical review letters 92, 207402 (2004).
74 C.-Y. Kuo et al., Single-domain multiferroic BiFeO3 films, Nature communications 7, 12712 (2016).
75 D. Pesquera et al., Surface symmetry-breaking and strain effects on orbital occupancy in transition metal perovskite epitaxial films, Nature communications 3, 1189 (2012).
76 G. van der Laan & B. Thole, Strong magnetic x-ray dichroism in 2p absorption spectra of 3d transition-metal ions, Physical Review B 43, 13401 (1991).
77 C. Aruta et al., Orbital occupation, atomic moments, and magnetic ordering at interfaces of manganite thin films, Physical Review B—Condensed Matter and Materials Physics 80, 014431 (2009).
78 Y. Tokura & N. Nagaosa, Orbital physics in transition-metal oxides, Science 288, 462-468 (2000).
79 C. Chen et al., Experimental confirmation of the X-ray magnetic circular dichroism sum rules for iron and cobalt, Physical review letters 75, 152 (1995).
80 D. Hovancik, J. Pospisil, K. Carva, V. Sechovsky & C. Piamonteze, Large orbital magnetic moment in VI3, Nano Letters 23, 1175-1180 (2023).
81 D. B. Williams, C. B. Carter, D. B. Williams & C. B. Carter. The transmission electron microscope. (Springer, 1996).
82 A. Weston. in Atomic and Electronic Properties of 2D Moiré Interfaces (ed A. Weston) 49-79 (Springer International Publishing, 2022).
83 S. V. Kalinin & A. Gruverman. Scanning probe microscopy: electrical and electromechanical phenomena at the nanoscale. Vol. 1 (Springer Science & Business Media, 2007).
84 U. Celano. The atomic force microscopy for nanoelectronics. (Springer, 2019).
85 L. Abelmann, A. van den Bos & C. Lodder. in Magnetic Microscopy of Nanostructures 253-283 (Springer, 2005).
86 O. Kazakova et al., Frontiers of magnetic force microscopy, Journal of applied Physics 125 (2019).
87 F. Li, Y. Zheng, C. Hua & J. Jian, Gas Sensing by Microwave Transduction: Review of Progress and Challenges, Frontiers in Materials 6 (2019).
88 Y. Ishibashi & M. Iwata, A theory of morphotropic phase boundary in solid-solution systems of perovskite-type oxide ferroelectrics, Japanese journal of applied physics 38, 800 (1999).
89 Y. Ishibashi & M. Iwata, Theory of morphotropic phase boundary in solid-solution systems of perovskite-type oxide ferroelectrics: Elastic properties, Japanese journal of applied physics 38, 1454 (1999).
90 G. Catalan et al., Flexoelectric rotation of polarization in ferroelectric thin films, Nature materials 10, 963-967 (2011).
91 Z. Li, M. Grimsditch, X. Xu & S.-K. Chan, The elastic, piezoelectric and dielectric constants of tetragonal PbTiO3 single crystals, Ferroelectrics 141, 313-325 (1993).
92 J. Joseph, T. Vimala, V. Sivasubramanian & V. Murthy, Structural investigations on Pb(ZrxT1−x)O3 solid solutions using the X-ray Rietveld method, Journal of materials science 35, 1571-1575 (2000).
93 D. Damjanovic, Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics, Reports on progress in physics 61, 1267 (1998).
94 D. Fasquelle & J. Carru, Electrical characterizations of PZT ceramics in large frequency and temperature ranges, Journal of the European Ceramic Society 28, 2071-2074 (2008).
95 S. Pandya et al., Understanding the role of ferroelastic domains on the pyroelectric and electrocaloric effects in ferroelectric thin films, Advanced Materials 31, 1803312 (2019).
96 T. Ohnishi, M. Lippmaa, T. Yamamoto, S. Meguro & H. Koinuma, Improved stoichiometry and misfit control in perovskite thin film formation at a critical fluence by pulsed laser deposition, Applied Physics Letters 87 (2005).
97 A. L. Roitburd, Equilibrium structure of epitaxial layers, physica status solidi (a) 37, 329-339 (1976).
98 L. Feigl et al., Controlled stripes of ultrafine ferroelectric domains, Nature Communications 5, 4677 (2014).
99 R. Xu et al., Ferroelectric polarization reversal via successive ferroelastic transitions, Nature Materials 14, 79-86 (2015).
100 J. Karthik, A. R. Damodaran & L. W. Martin, Effect of 90o Domain Walls on the Low-Field Permittivity of PbZr0.2Ti0.8O3 Thin Films, Physical Review Letters 108, 167601 (2012).
101 A. R. Damodaran et al., Three‐state ferroelastic switching and large electromechanical responses in PbTiO3 thin films, Advanced materials 29, 1702069 (2017).
102 M. Mtebwa et al., Room temperature concurrent formation of ultra-dense arrays of ferroelectric domain walls, Applied Physics Letters 107 (2015).
103 J. K. Lee et al., Direct observation of asymmetric domain wall motion in a ferroelectric capacitor, Acta Materialia 61, 6765-6777 (2013).
104 P. Gao et al., Atomic-scale mechanisms of ferroelastic domain-wall-mediated ferroelectric switching, Nature Communications 4, 2791 (2013).
105 L. Li, L. Xie & X. Pan, Real-time studies of ferroelectric domain switching: a review, Reports on Progress in Physics 82, 126502 (2019).
106 S. Pandya et al., Strain-induced growth instability and nanoscale surface patterning in perovskite thin films, Scientific reports 6, 26075 (2016).
107 V. Théry et al., Role of thermal strain in the metal-insulator and structural phase transition of epitaxial VO2 films, Physical Review B 93, 184106 (2016).
108 A. Sharma, Z.-G. Ban, S. Alpay & J. Mantese, Pyroelectric response of ferroelectric thin films, Journal of applied physics 95, 3618-3625 (2004).
109 Y. Yang et al., Thickness effects on the epitaxial strain states and phase transformations in (001)-VO2/TiO2 thin films, Journal of Applied Physics 125 (2019).
110 M. Mtebwa, A. Mazzalai, C. S. Sandu, A. Crassous & N. Setter, Engineered a/c domain patterns in multilayer (110) epitaxial Pb(Zr,Ti)O3 thin films: Impact on domain compliance and piezoelectric properties, AIP Advances 6 (2016).
111 M. Rossell et al., Atomic structure of highly strained BiFeO3 thin films, Physical review letters 108, 047601 (2012).
112 J. Agar et al., Highly mobile ferroelastic domain walls in compositionally graded ferroelectric thin films, Nature materials 15, 549-556 (2016).
113 F. Xu et al., Domain wall motion and its contribution to the dielectric and piezoelectric properties of lead zirconate titanate films, Journal of Applied Physics 89, 1336-1348 (2001).
114 L. Feigl, L. J. McGilly, C. S. Sandu & N. Setter, Compliant ferroelastic domains in epitaxial Pb(Zr,Ti)O3 thin films, Applied Physics Letters 104 (2014).
115 J. Ouyang et al., Engineering of Self-Assembled Domain Architectures with Ultra-high Piezoelectric Response in Epitaxial Ferroelectric Films, Advanced Functional Materials 17, 2094-2100 (2007).
116 S. M. Yang et al., Superdomain structure and high conductivity at the vertices in the (111)-oriented epitaxial tetragonal Pb(Zr,Ti)O3 thin film, Current Applied Physics 19, 418-423 (2019).
117 R. J. Zeches et al., A Strain-Driven Morphotropic Phase Boundary in BiFeO3, Science 326, 977-980 (2009).
118 H. Chang et al., Watching domains grow: In-situ studies of polarization switching by combined scanning probe and scanning transmission electron microscopy, Journal of Applied Physics 110 (2011).
119 X. Lin et al., Metallicity without quasi-particles in room-temperature strontium titanate, npj Quantum Materials 2, 41 (2017).
120 F. Sun et al., Reversible Mechanical Switching of Ferroelastic Stripe Domains in Multiferroic Thin Films, ACS Applied Materials & Interfaces 16, 32425-32433 (2024).
121 F. Rubio-Marcos, A. Del Campo, P. Marchet & J. F. Fernández, Ferroelectric domain wall motion induced by polarized light, Nature Communications 6, 6594 (2015).
122 Q. Yu et al., Orientation-dependent piezoelectricity and domain characteristics of tetragonal Pb(Zr0.3,Ti0.7)0.98Nb0.02O3 thin films on Nb-doped SrTiO3 substrates, Applied Physics Letters 104 (2014).
123 S. R. Bakaul et al., Ferroelectric domain wall motion in freestanding single‐crystal complex oxide thin film, Advanced Materials 32, 1907036 (2020).
124 H. Sun et al., Nonvolatile ferroelectric domain wall memory integrated on silicon, Nature Communications 13, 4332 (2022).
125 Q. Shi et al., The role of lattice dynamics in ferroelectric switching, Nature Communications 13, 1110 (2022).
126 T. J. Park, M. Cho, H.-S. Jung & C. S. Hwang. in High‐k Gate Dielectrics for CMOS Technology 77-110 (2012).
127 O. Ohtaka et al., Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature, Journal of the American Ceramic Society 84, 1369-1373 (2001).
128 O. Ohtaka et al., Phase relations and equations of state of ZrO2 under high temperature and high pressure, Physical Review B 63, 174108 (2001).
129 P. D. Lomenzo et al., Ferroelectric phenomena in Si-doped HfO2 thin films with TiN and Ir electrodes, Journal of Vacuum Science & Technology B 32 (2014).
130 M. H. Park et al., Ferroelectricity and antiferroelectricity of doped thin HfO2‐based films, Advanced Materials 27, 1811-1831 (2015).
131 M. Hyuk Park et al., Effect of forming gas annealing on the ferroelectric properties of Hf0.5Zr0.5O2 thin films with and without Pt electrodes, Applied Physics Letters 102 (2013).
132 H. Lee et al., Unveiling the Origin of Robust Ferroelectricity in Sub-2 nm Hafnium Zirconium Oxide Films, ACS Applied Materials & Interfaces 13, 36499-36506 (2021).
133 S. Salahuddin, K. Ni & S. Datta, The era of hyper-scaling in electronics, Nature Electronics 1, 442-450 (2018).
134 R. Materlik, C. Künneth & A. Kersch, The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model, Journal of Applied Physics 117 (2015).
135 M. Kobayashi, J. Wu, Y. Sawabe, S. Takuya & T. Hiramoto, Mesoscopic-scale grain formation in HfO2-based ferroelectric thin films and its impact on electrical characteristics, Nano Convergence 9, 50 (2022).
136 J. Wu, F. Mo, T. Saraya, T. Hiramoto & M. Kobayashi, A first-principles study on ferroelectric phase formation of Si-doped HfO2 through nucleation and phase transition in thermal process, Applied Physics Letters 117 (2020).
137 S. S. Cheema et al., Enhanced ferroelectricity in ultrathin films grown directly on silicon, Nature 580, 478-482 (2020).
138 S. Jo et al., Negative differential capacitance in ultrathin ferroelectric hafnia, Nature Electronics 6, 390-397 (2023).
139 S. Estandía et al., Engineering Ferroelectric Hf0.5Zr0.5O2 Thin Films by Epitaxial Stress, ACS Applied Electronic Materials 1, 1449-1457 (2019).
140 U. Schroeder, M. H. Park, T. Mikolajick & C. S. Hwang, The fundamentals and applications of ferroelectric HfO2, Nature Reviews Materials 7, 653-669 (2022).
141 T. Böscke, J. Müller, D. Bräuhaus, U. Schröder & U. Böttger, Ferroelectricity in hafnium oxide thin films, Applied Physics Letters 99 (2011).
142 J. Muller et al., Ferroelectricity in simple binary ZrO2 and HfO2, Nano letters 12, 4318-4323 (2012).
143 S. Clima et al., Identification of the ferroelectric switching process and dopant-dependent switching properties in orthorhombic HfO2: A first principles insight, Applied Physics Letters 104 (2014).
144 T. D. Huan, V. Sharma, G. A. Rossetti Jr & R. Ramprasad, Pathways towards ferroelectricity in hafnia, Physical Review B 90, 064111 (2014).
145 A. Kashir & H. Hwang, A CMOS-compatible morphotropic phase boundary, Nanotechnology 32, 445706 (2021).
146 Z. Wen & D. Wu, Ferroelectric tunnel junctions: modulations on the potential barrier, Advanced materials 32, 1904123 (2020).
147 S. S. Cheema et al., One Nanometer HfO2-Based Ferroelectric Tunnel Junctions on Silicon, Advanced Electronic Materials 8, 2100499 (2022).
148 H. Zhong et al., Large‐Scale Hf0.5Zr0.5O2 Membranes with Robust Ferroelectricity, Advanced Materials 34, 2109889 (2022).
149 S. J. Kim, J. Mohan, S. R. Summerfelt & J. Kim, Ferroelectric Hf0.5Zr0.5O2 thin films: A review of recent advances, Jom 71, 246-255 (2019).
150 M. H. Park et al., Surface and grain boundary energy as the key enabler of ferroelectricity in nanoscale hafnia-zirconia: A comparison of model and experiment, Nanoscale 9, 9973-9986 (2017).
151 Y. Wei et al., A rhombohedral ferroelectric phase in epitaxially strained Hf0.5Zr0.5O2 thin films, Nature Materials 17, 1095-1100 (2018).
152 M. Hyuk Park, H. Joon Kim, Y. Jin Kim, T. Moon & C. Seong Hwang, The effects of crystallographic orientation and strain of thin Hf0.5Zr0.5O2 film on its ferroelectricity, Applied Physics Letters 104 (2014).
153 C. Künneth, R. Materlik & A. Kersch, Modeling ferroelectric film properties and size effects from tetragonal interlayer in Hf1–xZrxO2 grains, Journal of Applied Physics 121 (2017).
154 M. H. Park, Y. H. Lee, T. Mikolajick, U. Schroeder & C. S. Hwang, Thermodynamic and Kinetic Origins of Ferroelectricity in Fluorite Structure Oxides, Advanced Electronic Materials 5, 1800522 (2019).
155 T. S. Böscke, J. Müller, D. Bräuhaus, U. Schröder & U. Böttger, Ferroelectricity in hafnium oxide thin films, Applied Physics Letters 99 (2011).
156 M. H. Park et al., A comprehensive study on the structural evolution of HfO2 thin films doped with various dopants, Journal of Materials Chemistry C 5, 4677-4690 (2017).
157 S. Starschich & U. Boettger, An extensive study of the influence of dopants on the ferroelectric properties of HfO2, Journal of Materials Chemistry C 5, 333-338 (2017).
158 Y. Goh, S. H. Cho, S.-H. K. Park & S. Jeon, Oxygen vacancy control as a strategy to achieve highly reliable hafnia ferroelectrics using oxide electrode, Nanoscale 12, 9024-9031 (2020).
159 X. J. Lou, M. Zhang, S. A. T. Redfern & J. F. Scott, Fatigue as a local phase decomposition: A switching-induced charge-injection model, Physical Review B 75, 224104 (2007).
160 D. Pesquera et al., Surface symmetry-breaking and strain effects on orbital occupancy in transition metal perovskite epitaxial films, Nature Communications 3, 1189 (2012).
161 F. M. F. de Groot et al., Oxygen 1s X-ray absorption edges of transition-metal oxides, Physical Review B 40, 5715-5723 (1989).
162 R. Vasić et al., Multi-technique x-ray and optical characterization of crystalline phase, texture, and electronic structure of atomic layer deposited Hf1−xZrxO2 gate dielectrics deposited by a cyclical deposition and annealing scheme, Journal of Applied Physics 113 (2013).
163 D.-Y. Cho, H.-S. Jung & C. S. Hwang, Structural properties and electronic structure of HfO2-ZrO2 composite films, Physical Review B 82, 094104 (2010).
164 M. Komatsu et al., Crystal structures and band offsets of ultrathin HfO2–Y2O3 composite films studied by photoemission and x-ray absorption spectroscopies, Applied physics letters 89 (2006).
165 L. Soriano et al., The O 1s x-ray absorption spectra of transition-metal oxides: The TiO2−ZrO2−HfO2 and V2O5−Nb2O5−Ta2O5 series, Solid state communications 87, 699-703 (1993).
166 L. Soriano, M. Abbate, J. Faber, C. Morant & J. Sanz, The electronic structure of ZrO2: Band structure calculations compared to electron and X-ray spectra, Solid state communications 93, 659-665 (1995).
167 C. Aruta et al., Evolution of magnetic phases and orbital occupation in (SrMnO3)n/(LaMnO3)2n superlattices, Physical Review B 80, 140405 (2009).
168 T. Mikolajick et al., Next generation ferroelectric materials for semiconductor process integration and their applications, Journal of Applied Physics 129 (2021).
169 S. J. Kim et al., Effect of film thickness on the ferroelectric and dielectric properties of low-temperature (400 °C) Hf0.5Zr0.5O2 films, Applied Physics Letters 112 (2018).
170 H. N. Lee et al., Suppressed dependence of polarization on epitaxial strain in highly polar ferroelectrics, Physical review letters 98, 217602 (2007).
171 M. Scigaj et al., Ultra-flat BaTiO3 epitaxial films on Si (001) with large out-of-plane polarization, Applied Physics Letters 102 (2013).
172 D. Padmapriya et al., Composition-dependent structural, electrical, magnetic and magnetoelectric properties of (1−x)BaTiO3−xCoFe2O4 particulate composites, Bulletin of Materials Science 43, 1-8 (2020).
173 L. K. Pradhan, R. Pandey, R. Kumar & M. Kar, Lattice strain induced multiferroicity in PZT-CFO particulate composite, Journal of Applied Physics 123 (2018).
174 C. Li et al., A comparative study on the structural, dielectric, ferroelectric and magnetic properties of CoFe2O4/PbZr0.52Ti0.48O3 multiferroic composite with different molar ratios, Journal of Physics Communications 3, 125010 (2019).
175 M. Muneeswaran, A. Akbari-Fakhrabadi, M. A. Gracia-Pinilla, J. C. Denardin & N. V. Giridharan, Realization of structural transformation for the enhancement of magnetic and magneto capacitance effect in BiFeO3–CoFe2O4 ceramics for energy storage application, Scientific Reports 11, 2265 (2021).
176 Y. Wang, F. Zahid, J. Wang & H. Guo, Structure and dielectric properties of amorphous high-k oxides: HfO2, ZrO2, and their alloys, Physical Review B 85, 224110 (2012).
177 Y.-C. Liu et al., Thickness-Dependent Ferroelectricity in Freestanding Hf0.5Zr0.5O2 Membranes, ACS Applied Electronic Materials (2024).
178 Z. Lu et al., Wafer-scale high-κ dielectrics for two-dimensional circuits via van der Waals integration, Nature Communications 14, 2340 (2023).
179 J. Lyu et al., Enhanced ferroelectricity in epitaxial Hf0.5Zr0.5O2 thin films integrated with Si(001) using SrTiO3 templates, Applied Physics Letters 114 (2019).
180 T. Onaya et al., Ferroelectricity of HfxZr1−xO2 thin films fabricated by 300 oC low temperature process with plasma-enhanced atomic layer deposition, Microelectronic Engineering 215, 111013 (2019).
181 J. Wang et al., Epitaxial BiFeO3 multiferroic thin film heterostructures, Science 299, 1719-1722 (2003).
182 W. Eerenstein, N. Mathur & J. F. Scott, Multiferroic and magnetoelectric materials, Nature 442, 759-765 (2006).
183 R. Ramesh & N. A. Spaldin, Multiferroics: progress and prospects in thin films, Nature materials 6, 21-29 (2007).
184 C. Ederer & N. A. Spaldin, Weak ferromagnetism and magnetoelectric coupling in bismuth ferrite, Physical Review B—Condensed Matter and Materials Physics 71, 060401 (2005).
185 Y.-H. Chu et al., Electric-field control of local ferromagnetism using a magnetoelectric multiferroic, Nature Materials 7, 478-482 (2008).
186 J.-G. Park, M. D. Le, J. Jeong & S. Lee, Structure and spin dynamics of multiferroic BiFeO3, Journal of Physics: Condensed Matter 26, 433202 (2014).
187 F. Bai et al., Destruction of spin cycloid in (111) c-oriented BiFeO3 thin films by epitiaxial constraint: enhanced polarization and release of latent magnetization, Applied Physics Letters 86 (2005).
188 T. Mitsui & J. Furuichi, Domain Structure of Rochelle Salt and KH2PO4, Physical Review 90, 193 (1953).
189 A. Roitburd, Equilibrium structure of epitaxial layers, Physica status solidi (a) 37, 329-339 (1976).
190 Y. E. Lozovik & V. Yudson, A new mechanism for superconductivity: pairing between spatially separated electrons and holes, Zh. Eksp. Teor. Fiz 71, 738 (1976).
191 S. t. Streiffer et al., Observation of Nanoscale 180° Stripe Domains in Ferroelectric PbTiO3 Thin Films, Physical review letters 89, 067601 (2002).
192 G. Catalan et al., Fractal dimension and size scaling of domains in thin films of multiferroic BiFeO3, Physical review letters 100, 027602 (2008).
193 Y. Chen et al., Ferroelectric domain structures of epitaxial (001) BiFeO3 thin films, Applied physics letters 90 (2007).
194 X. Deng et al., Strain engineering of epitaxial oxide heterostructures beyond substrate limitations, Matter 4, 1323-1334 (2021).
195 J. F. Scott, Nanoferroelectrics: statics and dynamics, Journal of Physics: Condensed Matter 18, R361 (2006).
196 V. Nagarajan et al., Thickness dependence of structural and electrical properties in epitaxial lead zirconate titanate films, Journal of Applied Physics 86, 595-602 (1999).
197 A. Haykal et al., Antiferromagnetic textures in BiFeO3 controlled by strain and electric field, Nature Communications 11, 1704 (2020).
198 A. K. Pradhan et al., Magnetic and electrical properties of single-phase multiferroic BiFeO3, Journal of Applied Physics 97 (2005).
199 M. Ramazanoglu et al., Local Weak Ferromagnetism in Single-Crystalline Ferroelectric BiFeO3, Physical Review Letters 107, 207206 (2011).
200 S. T. Zhang, M. H. Lu, D. Wu, Y. F. Chen & N. B. Ming, Larger polarization and weak ferromagnetism in quenched BiFeO3 ceramics with a distorted rhombohedral crystal structure, Applied Physics Letters 87 (2005).
201 J.-C. Yang et al., Electrically enhanced magnetization in highly strained BiFeO3 films, NPG Asia Materials 8, e269-e269 (2016).
202 K.-T. Ko et al., Concurrent transition of ferroelectric and magnetic ordering near room temperature, Nature communications 2, 567 (2011).