CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

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1.3.2 Ferrite-Ferroelectric Layered Heterostructures Ferrites (spinel, garnet or hexaferrite structure) have been long known as microwave materials due to their high permeability and resistivity. When used in tunable microwave devices, such as band-pass filters, phase shifters, or resonators, the microwave propagation behavior in these materials could be changed by variation of a bias dc magnetic field. This is because of the change of the permeability of the ferrites resulting from the changing bias magnetic field. This magnetic tuning is possible over a very wide frequency range, but it is slow and is associated with large power consumption. Another way of microwave tuning is using ferroelectric materials, in which electric field can be used to tune the dielectric constant of the materials and thus change their microwave properties. The tuning by electric field is fast and energy efficient, but usually the tunable frequency range is very narrow. A combination of ferrite and ferroelectric materials into composite or layered structures could provide the possibility of simultaneous magnetic and electric tuning.[40-43] This dual tuning allows the high efficiency of magnetic tuning and the high speed and low power requirements of electric tuning to be combined. For the work of this dissertation, only layered structure is introduced here. Studies on layered ferrite-ferroelectric structures have showed great importance for both fundamental understanding of high frequency magnetoelectric (ME) effect and various microwave applications. Two types of layered structures have been investigated. The first one is ME coupling in bonded bilayers, in which the deformation (strain) of the ferroelectric layer due to applied electric field results in a magnetic property change of the ferrite layer. Basically, this strain effect could change the internal magnetic field and thus generate shift of the ferromagnetic resonance (FMR) field. The degree of coupling depends on both the piezoelectric and magnetoelastic constants of the ferrite and ferroelectric material being used. The other type of 33
coupling is from unbound ferrite-ferroelectric bilayers, in which hybrid spin-electromagnetic oscillations and waves are formed.[44,45] Strong ME coupling behavior has been found in both type of structures. Fig. 11. ME coupling in a ferrite-ferroelectric layered structure. Reproduced with permission from ref. [46]. The degree of ME coupling effect is usually measured by the shift of FMR resonance curve. Fig.11 showed the ME effect in a unbound ferrite-ferroelectric bilayer structure.[46] The as used ferrite material is barium hexaferrite (BaM, BaFe12O19) and the ferroelectric materials is barium strontium titanate (BSTO, (Ba,Sr)TiO3). At a fixed resonance frequency (60 GHz), a FMR shift of 6 Oe is observed by applying 29 V voltage to the BSTO layer. To improve the ME coupling effect, high quality materials are essential for both ferrite and ferroelectric layers. Different thin film deposition methods have been investigated for the preparation of either the magnetic or the ferroelectric layer. However, to get both high quality and relatively thick (few microns to tens of microns) layers is still challenging. 34
Page 1 and 2: CHEMICAL VAPOR DEPOSITION OF THIN F
Page 3 and 4: ABSTRACT Chemical vapor deposition
Page 5 and 6: DEDICATION This dissertation is ded
Page 7 and 8: φ In-plane tilt angle of X-ray dif
Page 9 and 10: ACKNOWLEDGMENTS It is my pleasure t
Page 11 and 12: CONTENTS ABSTRACT .................
Page 13 and 14: 3.2.1 Introduction ................
Page 15 and 16: LIST OF TABLES Table 1. Hafnium ami
Page 17 and 18: indicated by the complex FMR curve.
Page 19 and 20: Fig. 49. Ferromagnetic resonance cu
Page 21 and 22: growth rate, good step coverage and
Page 23 and 24: growth of thin film oxides due to t
Page 25 and 26: one can uniformly deliver precursor
Page 27 and 28: for the next reaction step as shown
Page 29 and 30: Fig. 3. Schematic of a typical dire
Page 31 and 32: is predominantly dependent on syste
Page 33 and 34: J r J A -D n b-n 0 δ n or for the
Page 35 and 36: surface passivation with certain in
Page 37 and 38: ay spectroscopy (EDS), Wavelength d
Page 39 and 40: incidence angle is larger than cert
Page 41 and 42: epresenting those characteristic ph
Page 43 and 44: 1.2.3.3 X-ray Diffraction (XRD) X-r
Page 45 and 46: exhibit diffraction peaks in the no
Page 47 and 48: (nanometers to tens of nanometers),
Page 49 and 50: strongest absorption of microwave s
Page 51: pinch-off to indicate the lack of a
Page 55 and 56: diffusion barrier material in micro
Page 57 and 58: Fig. 14. A cross sectional scanning
Page 59 and 60: In spite of the same spinel structu
Page 61 and 62: ferrites has been investigated exte
Page 63 and 64: systems is showed in Fig.18.[83] As
Page 65 and 66: precursor vaporization process, e.g
Page 67 and 68: CHAPTER 3. PLASMA ENHANCED ATOMIC L
Page 69 and 70: the initial surface chemistry for t
Page 71 and 72: delay time of 2 seconds between spe
Page 73 and 74: Kcal/mol respectively. The stronger
Page 75 and 76: negative slope) behavior in the pum
Page 77 and 78: the existence of both physisorbed a
Page 79 and 80: decomposition products (Hf-H) and g
Page 81 and 82: dried by ultra high purity N2 gas.
Page 83 and 84: pressure for XPS analysis is around
Page 85 and 86: Hf and N elements, incorporation of
Page 87 and 88: [150,151] This is a unique feature
Page 89 and 90: software. The thickness results are
Page 91 and 92: CHAPTER 4. DIRECT LIQUID INJECTION
Page 93 and 94: film growth region. The properties
Page 95 and 96: solution was accurately controlled
Page 97 and 98: size). For the rocking curve analys
Page 99 and 100: oxygen does not participate in the
Page 101 and 102: ecause vapor velocity cannot be cha
Page 103 and 104:
Fig. 40. Cross-sectional view by fi
Page 105 and 106:
the MgAl2O4 substrate confirms cube
Page 107 and 108:
pattern. Fig.44(b) has diffraction
Page 109 and 110:
We have used an AGM (Alternating Gr
Page 111 and 112:
as derived equations for different
Page 113 and 114:
deposited at 600˚C is the lowest.
Page 115 and 116:
wave states degenerate with the FMR
Page 117 and 118:
Fig. 53. ϕ-scan of nickel ferrite
Page 119 and 120:
Surface roughness characterized by
Page 121 and 122:
Fig. 56. X-ray diffraction θ-2θ c
Page 123 and 124:
4.4 Conclusion In summary, we have
Page 125 and 126:
CHAPTER 5. DIRECT LIQUID INJECTION
Page 127 and 128:
eaction zone of the tube furnace is
Page 129 and 130:
Fig. 58. X-ray diffraction characte
Page 131 and 132:
interface. This phenomenon probably
Page 133 and 134:
6.1 Conclusion CHAPTER 6. CONCLUSIO
Page 135 and 136:
the temperature range of 600˚C to
Page 137 and 138:
such as PMN-PT and PZN-PT. CVD proc
Page 139 and 140:
[18]. L. S.-J. Peng, X. X. Xi, B. H
Page 141 and 142:
[54]. B. O. Johansson, J. -E. Sundg
Page 143 and 144:
[96]. J. D. Adam, S. V. Krishnaswam
Page 145 and 146:
[136]. J. Zhao, V. Fuflyigin, F. Wa
Page 147 and 148:
APPENDIX A: LabVIEW PROGRAM FOR PEA
Page 149 and 150:
APPENDIX B: TDMAH MOLECULAR STRUCTU
Page 151 and 152:
H 18 B19 2 A18 1 D17 H 18 B20 2 A19
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