Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...

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74 The absence of an intermediate polycrystalline layer along the interface shows that the growth did take place according to a two-step process with an initial carbonisation step achieved by only introducing the propane. 7.2.2 Stacking Faults and Partial Dislocations Fig. 7.4. Bright field TEM micrographs taken from the bulk of the 3C-SiC sample. B = [011], g = SF selected _ 11 1, s ≥ 0 Fig. 7.4. shows a set of low magnification bright-field TEM micrographs of different areas in the 3C-SiC representative of the bulk of the material. A high density of stacking faults (SF) are seen lying on the four {111} planes. Fringe contrast typical of stacking faults lying on inclined and edge-on planes is seen. The stacking faults are uniformly distributed throughout the foil. The preliminary results of tilting experiments in the electron microscope showed the fault vector of the SF to be of the type 1/3 with bonding partials of the type 1/6 i.e. the partials are of the Shockley type. This indicates that the fault was not formed as a result of the aggregation of point defects, which would form a Frank loop with Burgers vector of the type 1/3.
75 Fig. 7.5. The stacking fault selected for simulation with arrows pointing to the thickness fringes used for foil thickness determination To verify the suggested nature of the fault image, simulation and matching was performed. Fig. 7.5. shows a magnified bright field TEM micrograph of the SF shown in Fig. 7.4. This fault was selected for the simulation and the assumed fault vector and partial dislocation burgers vectors were used. Following this, the unknowns of the problem were determined starting with foil thickness. This was done using the thickness fringes present in the micrograph as well as the technique of convergent beam electron diffraction (CBED) (De Graef (2003)). Thickness fringe method Consider Fig. 7.5. It is known that the thickness fringes present in a bright field (or dark field) micrograph follow in increments of 1/2ξ (ξ is extinction distance) for each successive bright to dark fringe starting from the edge of the material (Hirsch et al. (1965)). Thus in this case the foil thickness was found to be approximately 2.75 ξ at the point of the fault using the thickness fringes as indicated. Using this and the extinction distance of the {111} reflection in 3C-SiC the thickness was determined to be ~ 188 nm. A value of 622 Å was used for the extinction distance and was found using Electron Diffraction (2003). 3 ξ ~2.75 ξ 2 ξ 5/2 ξ 3/2 ξ
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Analysis of the Extended Defects in
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My sincere thanks to the following
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OPSOMMING Hierdie dissertasie hande
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4.2.5. Two-Beam Scattering Matrix 4
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Dedicated to my wife and parents
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SUMMARY The dissertation focuses on
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CONTENTS Chapter 1: INTRODUCTION 1
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1 CHAPTER ONE INTRODUCTION Silicon
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2.1. Introduction 3 CHAPTER TWO OVE
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2.2.2 The Zinc-Blende Structure 5 T
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2.3 Point Defects, Defect Migration
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v m Em vm0 exp( ) (2.2) kT 9 wher
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11 explained and the concept of par
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13 Straight dislocations furthermor
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2.5 Partial Dislocations and Slip 1
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17 Fig. 2.13. The geometrical setup
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19 extrinsic stacking faults are th
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2.8 Twinning 21 Twinning is a proce
Page 37 and 38: 23 Fig. 2.20. The process of vacanc
Page 39 and 40: S n Td (3.2) 25 and is also referr
Page 41 and 42: 27 where a = a0(Z1 2/3 + Z2 2/3 ) -
Page 43 and 44: 29 Using this expression, curves of
Page 45 and 46: 31 As stated previously hard-sphere
Page 47 and 48: 33 where A is the atomic weight. Th
Page 49 and 50: 35 a vacancy dislocation loop if th
Page 51 and 52: 37 Fig. 4.1. (a) A wave incident on
Page 53 and 54: 39 Consider Fig. 4.2 which illustra
Page 55 and 56: 41 V0 is the mean inner potential o
Page 57 and 58: 43 beam left-hand side g' = 0 g' =
Page 59 and 60: 45 In addition another set of indep
Page 61 and 62: 47 When this is incorporated into t
Page 63 and 64: S ( s , z ) e T i Se ( / 0 )
Page 65 and 66: z0 z2 . xn cos and (4.47) D 1 proj
Page 67 and 68: 5.1 Introduction 53 CHAPTER FIVE LI
Page 69 and 70: 55 different orientations. The inte
Page 71 and 72: 57 Furthermore Pirouz et al. (1987)
Page 73 and 74: 59 intersection of the fault, the f
Page 75 and 76: 61 each nuclei because of the low s
Page 77 and 78: 63 (2000) found that subsequent ann
Page 79 and 80: 6.3.1 Ion Range and Defect Producti
Page 81 and 82: 67 Fig. 6.3. Total number of displa
Page 83 and 84: 7.1 Introduction 69 CHAPTER SEVEN R
Page 85 and 86: Fig. 7.2. Simulated diffraction pat
Page 87: 73 Fig. 7.3. A HRTEM image of the S
Page 91 and 92: (Si/ni) 2 0.000018 0.000016 0.00001
Page 93 and 94: 79 may be concluded that the initia
Page 95 and 96: 81 Fig. 7.11. Bright field TEM micr
Page 97 and 98: 83 Fig. 7.12 which was obtained by
Page 99 and 100: 85 Fig. 7.13. Bright-field TEM micr
Page 101 and 102: 87 (a) (b) Fig. 7.15. The (a) exper
Page 103 and 104: 89 In the following paragraphs the
Page 105 and 106: Fig. 7.18. CBED pattern taken of th
Page 107 and 108: 93 Table 7.5. The measured paramete
Page 109 and 110: 7.4.2 Results 95 Fig. 7.22. Bright-
Page 111 and 112: 97 Twin platelets on {111} planes
Page 113 and 114: 99 REFERENCES Blumenau, A.T., Jones
Page 115 and 116: 101 Hull, D., Bacon, D.J. : (1984)
Page 117: 103 Smith, D.J., Jepps, N.W. and Pa
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Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...

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