本論文藉由射頻磁控濺鍍法成長磁電複合薄膜。磁電複合材料是由壓電材料與鐵磁材料兩相複合形成的，本實驗合成兩種組合，即BiFeO3-CoFe2O4與BiFeO3-Co0.8Fe2.2O4，其中BiFeO3作為壓電相(piezoelectric)，CoFe2O4與Co0.8Fe2.2O4作為鐵磁相(ferromagnetic)，研究兩種組合磁電係數之差異。BiFeO3-CoFe2O4與BiFeO3-Co0.8Fe2.2O4複合薄膜使用雙靶共濺鍍的方式成長在LaNiO3/Si(100)基板上，其中LaNiO3作為底電極(bottom electrode)以及緩衝層(buffer layer)的作用，緩衝層可以減緩基板對薄膜的箝制效應(clamping effect)，以達到較高的磁電系數。經過調控濺鍍參數，在基板溫度700 °C、工作壓力30 mTorr、氬氣與氧氣流速比例為25:5、靶材功率BiFeO3 : 100 W, CoFe2O4/Co0.8Fe2.2O4 : 220 W條件下，並控制沉積速率，成長出BiFeO3-CoFe2O4與BiFeO3-Co0.8Fe2.2O4複合薄膜，經由XRD分析確認薄膜為兩組員之純相組成。磁電系數量測之感應電壓是沿垂直薄膜表面方向測量，所施加之磁場方向分為平行於 (Transverse mode)與垂直於 (Longitudinal mode)薄膜表面兩種模式，結果顯示兩種模式下BiFeO3-Co0.8Fe2.2O4的磁電系數均大於BiFeO3-CoFe2O4。實驗亦發現BiFeO3-Co0.8Fe2.2O4的磁電系數在兩種模式下相差很小，在頻率10 kHz下所測值都約為2.5 V/cm·Oe。而對於BiFeO3-CoFe2O4，Longitudinal 模式有明顯較大的磁電系數為2.21 V/cm·Oe，Transverse模式則為1.61 V/cm·Oe。此外，實驗中觀察到所有複合薄膜在低外加偏壓場，甚至無外加偏壓場就有滿大的磁電系數，推測此結果與複合薄膜內部具有殘留應力有關，而造成自偏壓(self-bias)的現象。

Thin films of magnetoelectric (ME) composites combining ferroelectric BiFeO3 and either ferrimagnetic CoFe2O4 or ferrimagnetic Co0.8Fe2.2O4 were deposited on LaNiO3-buffered Si substrates by means of dual-target RF magnetron co-sputtering technique. The conductive LaNiO3 buffer had a columnar nanostructure, which was used both as the bottom electrode and as a way to minimize the ''substrate clamp'' problem. By controlling sputtering parameters, the thin-film composites were deposited in an argon-oxygen atmosphere at a substrate temperature of 700 °C, and the sputtering power for the BiFeO3 and CoFe2O4 or Co0.8Fe2.2O4 targets was 100W and 220W, respectively. The phase formation, microstructure, and composition of the grown films were analyzed with a range of techniques. The ME voltage coefficients (αE) were measured vertically to the film with applied magnetic fields that were either vertical (longitudinal mode) or horizontal (transverse mode) to the film. The results indicated that the αE of BiFeO3-Co0.8Fe2.2O4 films was generally larger than that of the BiFeO3-CoFe2O4 films in both modes. For the BiFeO3-Co0.8Fe2.2O4 films, the achievable αE was similar in both modes, around 2.5 V/cm·Oe at the frequency of 10 kHz. For the BiFeO3-CoFe2O4 films, the αE measured in the longitudinal mode was notably higher than that measured in the transverse mode, both of which were the highest values recorded, 2.21 and 1.61 V/cm·Oe, respectively. In addition, we observed that all the thin-film composites had a large αE under zero applied magnetic fields. It was speculated that this result was related to the residual stress in the films, which caused self-bias behavior.

1. Pereira, N., et al., Magnetoelectrics: Three Centuries of Research Heading towards the 4.0 Industrial Revolution. Materials (Basel), 2020. 13(18).
2. Palneedi, H., et al., Status and Perspectives of Multiferroic Magnetoelectric Composite Materials and Applications. Actuators, 2016. 5(1).
3. Cho, K.-H. and S. Priya, Direct and converse effect in magnetoelectric laminate composites. Applied Physics Letters, 2011. 98(23).
4. Vopson, M.M., Fundamentals of Multiferroic Materials and Their Possible Applications. Critical Reviews in Solid State and Materials Sciences, 2015. 40(4): p. 223-250.
5. Wadhawan, V., Introduction to ferroic materials. 2000: CRC press.
6. Ortega, N., et al., Multifunctional magnetoelectric materials for device applications. Journal of Physics: Condensed Matter, 2015. 27(50): p. 504002.
7. Bertaut, E. and M. Mercier, Structure magnetique de MnYO3. Physics Letters, 1963. 5(1).
8. Kamenetskii, E.O., M. Sigalov, and R. Shavit, Tellegen particles and magnetoelectric metamaterials. Journal of Applied Physics, 2009. 105(1).
9. Van den Boomgaard, J. and R. Born, A sintered magnetoelectric composite material BaTiO 3-Ni (Co, Mn) Fe 2 O 4. Journal of Materials Science, 1978. 13(7): p. 1538-1548.
10. Van den Boomgaard, J., et al., An in situ grown eutectic magnetoelectric composite material. Journal of Materials Science, 1974. 9(10): p. 1705-1709.
11. Nan, C.-W., et al., Multiferroic magnetoelectric composites: Historical perspective, status, and future directions. Journal of Applied Physics, 2008. 103(3).
12. Nan, C.-W., Physics of inhomogeneous inorganic materials. Progress in materials science, 1993. 37(1): p. 1-116.
13. Nan, C.W., et al., Coupled magnetic–electric properties and critical behavior in multiferroic particulate composites. Journal of Applied Physics, 2003. 94(9): p. 5930-5936.
14. Newnham, R., D. Skinner, and L. Cross, Connectivity and piezoelectric-pyroelectric composites. Materials Research Bulletin, 1978. 13(5): p. 525-536.
15. Islam, R.A., et al., Effect of gradient composite structure in cofired bilayer composites of Pb(Zr0.56Ti0.44)O3–Ni0.6Zn0.2Cu0.2Fe2O4 system on magnetoelectric coefficient. Journal of Materials Science, 2008. 43(18): p. 6337-6343.
16. Islam, R.A., et al., Magnetoelectric properties of core-shell particulate nanocomposites. Journal of Applied Physics, 2008. 104(10).
17. Lam, K.H., C.Y. Lo, and H.L.W. Chan, Frequency response of magnetoelectric 1–3-type composites. Journal of Applied Physics, 2010. 107(9).
18. Ma, J., Z. Shi, and C.W. Nan, Magnetoelectric Properties of Composites of Single Pb(Zr,Ti)O3 Rods and Terfenol-D/Epoxy with a Single-Period of 1-3-Type Structure. Advanced Materials, 2007. 19(18): p. 2571-2573.
19. Islam, R.A., et al., Giant magnetoelectric effect in sintered multilayered composite structures. Journal of Applied Physics, 2008. 104(4).
20. Wang, Y., et al., An extremely low equivalent magnetic noise magnetoelectric sensor. Adv Mater, 2011. 23(35): p. 4111-4.
21. McDannald, A., et al., Magnetoelectric coupling in solution derived 3-0 type PbZr0.52Ti0.48O3:xCoFe2O4 nanocomposite films. Applied Physics Letters, 2013. 102(12).
22. Aimon, N.M., et al., Multiferroic behavior of templated BiFeO3-CoFe2O4 self-assembled nanocomposites. ACS Appl Mater Interfaces, 2015. 7(4): p. 2263-8.
23. Lage, E., et al., Exchange biasing of magnetoelectric composites. Nat Mater, 2012. 11(6): p. 523-9.
24. Palneedi, H., et al., Enhanced off-resonance magnetoelectric response in laser annealed PZT thick film grown on magnetostrictive amorphous metal substrate. Applied Physics Letters, 2015. 107(1).
25. Röntgen, W.C., Ueber die durch Bewegung eines im homogenen electrischen Felde befindlichen Dielectricums hervorgerufene electrodynamische Kraft. Annalen der Physik, 1888. 271(10): p. 264-270.
26. Wilson, H.A., III. On the electric effect of rotating a dielectric in a magnetic field. Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character, 1905. 204(372-386): p. 121-137.
27. Curie, P., Sur la symétrie dans les phénomènes physiques, symétrie d'un champ électrique et d'un champ magnétique. Journal de physique théorique et appliquée, 1894. 3(1): p. 393-415.
28. Debye, P., Bemerkung zu einigen neuen Versuchen über einen magneto-elektrischen Richteffekt. Zeitschrift für Physik, 1926. 36(4): p. 300-301.
29. Astrov, D., S. Novikova, and M. Orlova, SHIFT OF THE CURIE TEMPERATURE BY HYDROSTATIC COMPRESSION OF MANGANESE AND COBALT FLUORIDES. SOVIET PHYSICS JETP, 1960. 37(10).
30. Astrov, D., Magnetoelectric effect in chromium oxide. Sov. Phys. JETP, 1961. 13(4): p. 729-733.
31. Rado, G. and V. Folen, Observation of the magnetically induced magnetoelectric effect and evidence for antiferromagnetic domains. Physical review letters, 1961. 7(8): p. 310.
32. Fiebig, M., Revival of the magnetoelectric effect. Journal of physics D: applied physics, 2005. 38(8): p. R123.
33. Santoro, R. and R. Newnham. SURVEY OF MAGNETOELECTRIC MATERIALS. 1966.
34. Brown Jr, W., R. Hornreich, and S. Shtrikman, Upper bound on the magnetoelectric susceptibility. Physical Review, 1968. 168(2): p. 574.
35. Sun, N.X. and G. Srinivasan, Voltage Control of Magnetism in Multiferroic Heterostructures and Devices. Spin, 2013. 02(03).
36. Paluszek, M., et al., Magnetoelectric composites for medical application, in Composite Magnetoelectrics. 2015. p. 297-327.
37. Fang, C., et al., Significant reduction of equivalent magnetic noise by in-plane series connection in magnetoelectric Metglas/Mn-doped Pb(Mg1/3Nb2/3)O3-PbTiO3laminate composites. Journal of Physics D: Applied Physics, 2015. 48(46).
38. Annapureddy, V., et al., Low‐Loss Piezoelectric Single‐Crystal Fibers for Enhanced Magnetic Energy Harvesting with Magnetoelectric Composite. Advanced Energy Materials, 2016. 6(24).
39. Patil, D.R., et al., Anisotropic self-biased dual-phase low frequency magneto-mechano-electric energy harvesters with giant power densities. APL Materials, 2014. 2(4).
40. Ryu, J., et al., Ubiquitous magneto-mechano-electric generator. Energy & Environmental Science, 2015. 8(8): p. 2402-2408.
41. Hu, J.-M., et al., Multiferroic magnetoelectric nanostructures for novel device applications. MRS Bulletin, 2015. 40(9): p. 728-735.
42. Heron, J.T., et al., Electric-field-induced magnetization reversal in a ferromagnet-multiferroic heterostructure. Phys Rev Lett, 2011. 107(21): p. 217202.
43. Biswas, A.K., et al., Experimental demonstration of complete 180 reversal of magnetization in isolated Co nanomagnets on a PMN–PT substrate with voltage generated strain. Nano letters, 2017. 17(6): p. 3478-3484.
44. Liu, M., et al., Voltage-impulse-induced non-volatile ferroelastic switching of ferromagnetic resonance for reconfigurable magnetoelectric microwave devices. Adv Mater, 2013. 25(35): p. 4886-92.
45. 吳金俊, 沉積鎳酸鑭奈米柱狀晶緩衝層應用於鎳鋅鐵氧-鐵酸鉍複合材料薄膜之成長, in 材料科學及工程學系. 2018, 國立成功大學: 台南市. p. 83.
46. Bozorth, R., E.F. Tilden, and A.J. Williams, Anisotropy and magnetostriction of some ferrites. Physical Review, 1955. 99(6): p. 1788.
47. Wu, J., et al., Multiferroic bismuth ferrite-based materials for multifunctional applications: ceramic bulks, thin films and nanostructures. Progress in Materials Science, 2016. 84: p. 335-402.
48. Kadomtseva, A.M., et al., Phase transitions in multiferroic BiFeO3 crystals, thin-layers, and ceramics: enduring potential for a single phase, room-temperature magnetoelectric ‘holy grail’. Phase Transitions, 2006. 79(12): p. 1019-1042.
49. Ederer, C. and N.A. Spaldin, Weak ferromagnetism and magnetoelectric coupling in bismuth ferrite. Physical Review B, 2005. 71(6): p. 060401.
50. Miszczyk, A. and K. Darowicki, Study of anticorrosion and microwave absorption properties of NiZn ferrite pigments. Anti-Corrosion Methods and Materials, 2011.
51. Goldman, A., Modern ferrite technology. 2006: Springer Science & Business Media.
52. Hou, Y., et al., Structural, electronic and magnetic properties of partially inverse spinel CoFe2O4: a first-principles study. Journal of Physics D: Applied Physics, 2010. 43(44): p. 445003.
53. Srivastava, C., G. Srinivasan, and N. Nanadikar, Exchange constants in spinel ferrites. Physical Review B, 1979. 19(1): p. 499.
54. Buschow, K.H.J. and F.R. Boer, Physics of magnetism and magnetic materials. Vol. 7. 2003: Springer.
55. Meiklejohn, W.H. and C.P. Bean, New Magnetic Anisotropy. Physical Review, 1956. 102(5): p. 1413-1414.
56. Nogués, J., et al., Role of interfacial structure on exchange-biased FeF 2− Fe. Physical Review B, 1999. 59(10): p. 6984.
57. Nogués, J. and I.K. Schuller, Exchange bias. Journal of Magnetism and Magnetic Materials, 1999. 192(2): p. 203-232.
58. Sung, H.W. and C. Rudowicz, A closer look at the hysteresis loop for ferromagnets. Department of Physics and Materials Science, City University of Hong Kong, 2010.
59. Ekreem, N.B., et al., An overview of magnetostriction, its use and methods to measure these properties. Journal of Materials Processing Technology, 2007. 191(1-3): p. 96-101.
60. Hall, D., et al. Ferroelectric hysteresis measurement & analysis. in Minutes of the NPL CAM7 IAG Meeting. 1998.
61. Abegunde, O.O., et al., Overview of thin film deposition techniques. AIMS Materials Science, 2019. 6(2): p. 174-199.
62. Perez garcia, R., Controlled Deposition of Fullerenes: Effects of Topological nano-Modifications of a Surface on Aggregation and Growth Phenomena. 2018.
63. Movchan, B.A. and A. Demchishin, STRUCTURE AND PROPERTIES OF THICK CONDENSATES OF NICKEL, TITANIUM, TUNGSTEN, ALUMINUM OXIDES, AND ZIRCONIUM DIOXIDE IN VACUUM. Fiz. Metal. Metalloved. 28: 653-60 (Oct 1969). 1969.
64. Thornton, J.A., High rate thick film growth. Annual review of materials science, 1977. 7(1): p. 239-260.
65. Messier, R., A. Giri, and R. Roy, Revised structure zone model for thin film physical structure. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1984. 2(2): p. 500-503.
66. 林蔚叡, 以鐵酸鉍複鐵式材料為釘札層製作全氧化物自旋閥之研究, in 材料科學及工程學系. 2014, 國立成功大學: 台南市. p. 121.
67. Epp, J., X-ray diffraction (XRD) techniques for materials characterization, in Materials characterization using nondestructive evaluation (NDE) methods. 2016, Elsevier. p. 81-124.
68. Simeone, D., et al., Grazing incidence X-ray diffraction for the study of polycrystalline layers. Thin Solid Films, 2013. 530: p. 9-13.
69. Zhou, W., et al., Fundamentals of scanning electron microscopy (SEM), in Scanning microscopy for nanotechnology. 2006, Springer. p. 1-40.
70. Burgei, W., M.J. Pechan, and H. Jaeger, A simple vibrating sample magnetometer for use in a materials physics course. American Journal of Physics, 2003. 71(8): p. 825-828.
71. Kumar, M.M., et al., An experimental setup for dynamic measurement of magnetoelectric effect. Bulletin of Materials Science, 1998. 21(3): p. 251-255.
72. Amplifier, D.L.-I., MODEL SR830. Interface, 1993. 4: p. 24.
73. Qi, X., et al., Ferroelectric properties and dielectric responses of multiferroic BiFeO3 films grown by RF magnetron sputtering. Journal of Physics D: Applied Physics, 2008. 41(23): p. 232001.
74. Qi, X., et al., Growth and characterisation of multiferroic BiFeO3 films with fully saturated ferroelectric hysteresis loops and large remanent polarisations. Journal of the European Ceramic Society, 2010. 30(2): p. 283-287.
75. Qi, X., et al., Optimal growth windows of multiferroic BiFeO3 films and characteristics of ferroelectric domain structures. Thin Solid Films, 2009. 517(20): p. 5862-5866.
76. Liu, M., et al., A modified sol-gel process for multiferroic nanocomposite films. Journal of Applied Physics, 2007. 102(8): p. 083911.
77. Srinivasan, G., et al., Giant magnetoelectric effects in layered composites of nickel zinc ferrite and lead zirconate titanate. Solid State Communications, 2002. 124(10-11): p. 373-378.
78. Lin, W.-J., W.-C. Chang, and X. Qi, Exchange bias and magneto-resistance in an all-oxide spin valve with multi-ferroic BiFeO3 as the pinning layer. Acta materialia, 2013. 61(19): p. 7444-7453.
79. Lu, S.-Z. and X. Qi, RF magnetron co-sputtering growth and characterisation of multiferroic composite film Ni0.5Zn0.5Fe2O4 + BiFeO 3. J. Mater. Chem. C, 2016. 4: p. 8679-8686.
80. 朱玉荃, 射頻磁控濺鍍法成長鐵酸鉍-鈷鋅鐵氧複合材料, in 材料科學及工程學系. 2020, 國立成功大學: 台南市. p. 84.
81. 陳冠倫, 不同Ni/Zn比例對於鎳鋅鐵氧-鐵酸鉍複合材料磁電性質影響之研究, in 材料科學及工程學系. 2019, 國立成功大學: 台南市. p. 92.
82. Franco Junior, A., V. Zapf, and P. Egan, Magnetic properties of nanoparticles of Co x Fe (3− x) O 4 (0.05⩽ x⩽ 1.6) prepared by combustion reaction. Journal of applied physics, 2007. 101(9): p. 09M506.
83. Khodaei, M., et al., (111)-Oriented Co0.8Fe2.2O4+δ thin film grown by pulsed laser deposition: Structural and magnetic properties. Journal of Materials Science, 2013. 48: p. 6960-6969.
84. Cullity, B.D. and C.D. Graham, Introduction to magnetic materials. 2011: John Wiley & Sons.
85. Margulies, D., et al., Origin of the anomalous magnetic behavior in single crystal Fe 3 O 4 films. Physical Review Letters, 1997. 79(25): p. 5162.
86. McDannald, A., et al., Switchable 3-0 magnetoelectric nanocomposite thin film with high coupling. Nanoscale, 2017. 9(9): p. 3246-3251.
87. Lam, K.H., C. Lo, and H.L. Chan, Frequency response of magnetoelectric 1–3-type composites. Journal of applied physics, 2010. 107(9): p. 093901.
88. Cho, K.-H., Effect of structural control on the magnetoelectric characteristics of piezoelectric–magnetostrictive laminate composite in resonance and off-resonance modes. Electronic Materials Letters, 2019. 15(5): p. 555-561.
89. Ryu, H., et al., Magnetoelectric effects of nanoparticulate Pb (Zr 0.52 Ti 0.48) O 3–Ni Fe 2 O 4 composite films. Applied Physics Letters, 2006. 89(10): p. 102907.
90. Nlebedim, I., et al., Anisotropy and magnetostriction in non-stoichiometric cobalt ferrite. IEEE transactions on magnetics, 2012. 48(11): p. 3084-3087.
91. Liu, Y., et al., Effect of magnetic bias field on magnetoelectric coupling in magnetoelectric composites. Journal of applied physics, 2003. 94(8): p. 5118-5122.
92. Wan, J., et al., Magnetoelectric CoFe 2 O 4–Pb (Zr, Ti) O 3 composite thin films derived by a sol-gel process. Applied Physics Letters, 2005. 86(12): p. 122501.
93. Anantharamaiah, P. and P. Joy, Enhancing the strain sensitivity of CoFe 2 O 4 at low magnetic fields without affecting the magnetostriction coefficient by substitution of small amounts of Mg for Fe. Physical Chemistry Chemical Physics, 2016. 18(15): p. 10516-10527.
94. Zhou, Y., et al., Self-biased magnetoelectric composites: an overview and future perspectives. Energy Harvest. Syst, 2016. 3(1): p. 1.