CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

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(αMgO = 1.0×10 -5 K -1 , αNiFe2O4 = 1.34×10 -5 K -1 ). A detailed analysis of stress development between nickel ferrite film and MgO substrate during CVD growth has been reported by Fitzgerald et al.[82] Careful examination of the surface cracks in our films with FE-SEM (Field Emission Scanning Electron Microscopy) interestingly reveals bent fractured rectangular lamina pointing out of the surface consisting of both the nickel ferrite film and a layer of the MgO substrate. The MgO layer thickness is about the same of that of the nickel ferrite film. It appears that the residual interfacial stress is sufficiently large to fracture the MgO crystal but not the interfacial bond between the film and MgO. Apart from the extremely large tensile stress build-up, it is speculated that the crystalline defects generated by the Mg diffusion into nickel ferrite films can also weaken the strength of MgO crystal. Surface cracks in nickel ferrite films on MgO (100) substrate have previously been observed in films grown using pulsed laser deposition,[101] but no details are provided regarding their formation mechanism. As can be seen in Fig.40(a) and (b), films grown on both MgAl2O4 and MgO exhibit increased surface roughness of ~20 nm for the highest deposition temperature of 800˚C. No surface cracks are observed on MgO substrate for this deposition temperature probably due to relaxation of the interfacial stress by the increased roughness. As for the low temperature deposition at 500˚C, growth on the two substrates shows completely different morphology. Nickel ferrite films on MgAl2O4 display similar morphology as those deposited at 600 and 700˚C, but films on MgO show voided columnar structure (Fig.40(d)), as expected for low temperature epitaxial growth due to limited surface diffusion. Apparently, for nickel ferrite growth at 500˚C, the MgAl2O4 (100) surface provides larger surface diffusivity than the MgO (100) surface. 83
Fig. 40. Cross-sectional view by field emission scanning electron microscopy; (a) nickel ferrite on MgAl2O4 (100) deposited at 500~800˚C; (b) nickel ferrite on MgO(100) deposited at 500~800˚C; (c) Magnified view of nickel ferrite on MgAl2O4 deposited at 600˚C, the 5 × 5 μm 2 AFM image shows the film surface RMS roughness of ~0.3 nm; (d) Magnified and tilted (10˚) view of nickel ferrite on MgO(100) deposited at 500˚C with RMS roughness of ~30 nm. 4.2.2.1.3 Physical properties Due to the formation of surface cracks in films on MgO (100) substrates that complicate analysis of film properties, we focus here on results for growth on MgAl2O4 (100) substrates. The crystalline structure of the as-deposited films has been analyzed using an X-ray diffractometer (Philips X’pert Pro, Cu Kα source). As shown in Fig.41, all the films deposited between 500˚C to 800˚C exhibit a pure spinel phase with the (h00) planes parallel to the film surface. The calculated out-of-plane lattice parameters are 0.833, 0.834, 0.834, and 0.831 nm for films grown at 500, 600, 700 and 800˚C, respectively. The films grown at 500-700˚C have lattice 84
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CHEMICAL VAPOR DEPOSITION OF THIN F
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ABSTRACT Chemical vapor deposition
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DEDICATION This dissertation is ded
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φ In-plane tilt angle of X-ray dif
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ACKNOWLEDGMENTS It is my pleasure t
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CONTENTS ABSTRACT .................
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3.2.1 Introduction ................
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LIST OF TABLES Table 1. Hafnium ami
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indicated by the complex FMR curve.
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Fig. 49. Ferromagnetic resonance cu
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growth rate, good step coverage and
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growth of thin film oxides due to t
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one can uniformly deliver precursor
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for the next reaction step as shown
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Fig. 3. Schematic of a typical dire
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is predominantly dependent on syste
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J r J A -D n b-n 0 δ n or for the
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surface passivation with certain in
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ay spectroscopy (EDS), Wavelength d
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incidence angle is larger than cert
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epresenting those characteristic ph
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1.2.3.3 X-ray Diffraction (XRD) X-r
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exhibit diffraction peaks in the no
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(nanometers to tens of nanometers),
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strongest absorption of microwave s
Page 51 and 52: pinch-off to indicate the lack of a
Page 53 and 54: coupling is from unbound ferrite-fe
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: ecause vapor velocity cannot be cha
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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