CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

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experiments at a deposition temperature of 700˚C on both MgAl2O4 (100) and MgO (100) substrates. The first experiment involves film growth without any oxygen flow (just the argon carrier gas). Film growth by thermal decomposition of the metal chelate precursors occurs in the absence of oxygen.[108] However, as can be seen from the SEM micrograph image in Fig.39 (a), the as-deposited film shows a very porous structure. EDX (Energy Dispersive X-ray Spectroscopy) analysis reveals the presence of a significant excess of Fe than in stoichiometric nickel ferrite, along with trace amounts of carbon (< 2%). The porous structure is likely related to incomplete decomposition together with the slow kinetics of the surface reaction and/or desorption of the by-products. Based on thermal stability studies of the precursors, the preferential incorporation of iron may be attributed to the lower thermal stability of Fe(acac)3 than Ni(acac)2.[156-158] The effect of high oxygen flow rate, double of what is needed for growth of smooth and stoichiometric films (Table 4), is studied in the second control experiment. As shown in Fig.39(b), a relatively smooth and dense film is obtained. The correct chemical composition (Ni:Fe = 1:2) is obtained under this condition. However, small particles (10-100 nm range) are observed on the film surface. The particulate formation can be attributed to gas phase nucleation, which is a common and undesirable feature in CVD reactions, especially at high reaction pressures. Particulates buried in the film during growth can result in crystalline defects and thus influence the physical properties. It is noteworthy that the film growth rate does not increase with the increased oxygen flow rate. Comparing the results of these two experiments, the oxygen flow influences the thin film growth kinetics and helps balance the deposition rates of Ni and Fe. It is likely that more of lower molecular weight volatile products, such as CO2, are generated in the presence of oxygen and thus minimize the problem of blocked surface adsorption sites. Based on mass spectrometry studies Igumenov et al. [159] suggest that the 79
oxygen does not participate in the formation of the oxide phase during thermal decomposition of metal β-deketonates. Instead, its role is primarily to oxidize the organic fragments to form smaller molecular weight products and thus avoid carbon incorporation in the film. This is consistent with our observations from the above control experiments. Earlier mass spectrometry studies have shown that thermal decomposition of Ni(acac)2 results in the formation of methane in addition to acetone and carbon dioxide formed with Fe(acac)3.[156] In the presence of oxygen, the preferential consumption of methane can drive the reaction equilibrium towards thermal decomposition and thus increase the rate of Ni incorporation into the film. Moreover, enhanced surface reaction kinetics in the presence of oxygen can alter the film growth mode to a mass transfer limited process where the incorporation rate of Ni and Fe is actually dependent on their diffusion rates through the gas-phase boundary layer above the surface as discussed later. 4.2.2.1.2 Thin Film Growth Mode Table 5. Characteristics of nickel ferrite films deposited at different substrate temperatures. Substrate temperature (˚C) Growth rate (μm hr) RMS roughness (nm) Ni:Fe atomic ratio MgAl2O4 MgO MgAl2O4 MgO MgAl2O4 MgO 500 0.65 1.10 0.17 30.0 1:2.02 1:2.06 600 0.75 0.64 0.23 0.14 1:2.09 1:2.10 700 0.62 0.56 0.34 0.16 1:2.08 1:2.09 800 0.68 0.80 18.8 22.0 1:2.01 1:1.99 We have grown nickel ferrite films on MgAl2O4 (100) and MgO (100) at temperatures ranging from 500˚C to 800˚C under optimized vaporization conditions and oxygen flow rate. The corresponding film growth rates, surface roughness (RMS), and chemical compositions are listed in Table 5. The film growth rate does not show a clear trend with increasing temperature. 80
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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
Page 47 and 48: (nanometers to tens of nanometers),
Page 49 and 50: 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: size). For the rocking curve analys
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
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APPENDIX B: TDMAH MOLECULAR STRUCTU
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H 18 B19 2 A18 1 D17 H 18 B20 2 A19
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