CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

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Fig. 1. Schematic of a typical CVD system with a horizontal tube reactor. The precursor selection is an important factor which can greatly affect the CVD processing conditions and the grown thin film qualities. Generally, few properties have to be considered before selecting an appropriate precursor, such as, volatility, thermal stability and potential impurity formation in the grown films. The chemicals often used as CVD precursors include metal halides, metal alkyls, metal cyclopentadienyls, metal alkoxides and metal β- diketonates, etc.. Metal halides as the simplest inorganic precursors are highly reactive and thermally stable, but their vaporization require high temperatures and they produce corrosive gaseous by-products that etch the film constituents or the reactor walls and pump parts. Metal alkyls have reactive metal carbon bonds and therefore low thermal energy is needed for deposition of like metal oxides. The small alkyl ligands can minimize steric hindrance and generate volatile and relatively inert by-products, which can ameliorate readsorption and corrosion effects. However, the selection of metal alkyls is always limited by the number of available metal elements that exist in this format. The low thermal stability of these precursors is another problem needs to be considered. Metal cyclopentadienyls are usually available for alkaline earth metals. They also have active metal carbon bonds and produce hydrocarbon by products. The potential issue with this kind of precursor is film contamination by carbon and/or hydrogen elements from the precursor decomposition.[5] Metal alkoxides are used only for the 3
growth of thin film oxides due to the highly strong metal oxygen bond. Generally, low temperature decomposition can generate the desired oxide. Metal β-diketonates also have a strong metal oxygen bond. The oxidant used is usually ozone instead of oxygen or water vapor. A marked issue with these precursors is the effect of steric hindrance, which might leave unoccupied surface sites and decrease the grown film density. Metal alkylamides have relatively high volatility and active metal nitrogen bonds for reaction with oxidants. It has been found in certain chemical vapor deposition research that this kind of precursors would show some 'readsorption' behavior and little information is known about the reaction by-products.[5] All the precursors mentioned above have their own advantages and disadvantages. To make the best selection, all the precursor properties have to be considered comprehensively. As mentioned earlier, the selection of precursor is also dependent on the specific type of CVD technique. The following few paragraphs will introduce the basic classifications. The CVD technique can be classified into different types due to different standards of classification. For example, based on the operation pressure, it can be divided into low pressure CVD (LPCVD), ultrahigh vacuum CVD (UHVCVD) and atmospheric CVD (APCVD). It's apparent CVD technique can be operated in an environment with a much wider pressure window than PVD methods, which are often operated under ultrahigh vacuum conditions, for example, thermal/e-beam evaporation and molecular beam epitaxy. Usually, the lower the system pressure, the less contamination issues plague thin film growth. However, the decreased pressure is accompanied with a lower film grow rate. Another way of classification of the CVD technique is based on different energy types applied to overcome the activation energy barriers of breaking bonds, such as, thermal CVD, electron beam CVD,[6] laser CVD and plasma enhanced CVD (PECVD). Among these, PECVD has been extensively studied in the past, especially for thin 4
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: growth rate, good step coverage and
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 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
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negative slope) behavior in the pum
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the existence of both physisorbed a
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decomposition products (Hf-H) and g
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dried by ultra high purity N2 gas.
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pressure for XPS analysis is around
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Hf and N elements, incorporation of
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[150,151] This is a unique feature
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software. The thickness results are
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CHAPTER 4. DIRECT LIQUID INJECTION
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film growth region. The properties
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solution was accurately controlled
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size). For the rocking curve analys
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oxygen does not participate in the
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ecause vapor velocity cannot be cha
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Fig. 40. Cross-sectional view by fi
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the MgAl2O4 substrate confirms cube
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pattern. Fig.44(b) has diffraction
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We have used an AGM (Alternating Gr
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as derived equations for different
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deposited at 600˚C is the lowest.
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wave states degenerate with the FMR
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Fig. 53. ϕ-scan of nickel ferrite
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Surface roughness characterized by
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Fig. 56. X-ray diffraction θ-2θ c
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4.4 Conclusion In summary, we have
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CHAPTER 5. DIRECT LIQUID INJECTION
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eaction zone of the tube furnace is
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Fig. 58. X-ray diffraction characte
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interface. This phenomenon probably
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6.1 Conclusion CHAPTER 6. CONCLUSIO
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the temperature range of 600˚C to
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such as PMN-PT and PZN-PT. CVD proc
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[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
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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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