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

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(a) (b) 6 Fig. 2.4. Stacking sequences of the zinc-blende structure for the (a) {100} and (b) {111} planes A A' B B' A A' B B' A A' B B' The two consecutive layers of the constituent atoms in the same type of configuration are considered as a single plane consisting of a double layer of Si and C atoms. Thus a ABABAB… or ABCABC… stacking sequence as in the case for the fcc structure results with the only difference being that a layer contains both the constituent atoms. -SiC is a cubic phase of SiC with a zinc-blende structure as shown in Fig. 2.3. The {110} planes consist of double layers of Si and C atoms. Also the stacking sequence for the {100} and {110} planes are AA'BB'AA'… and AA'BB'CC' for the {111} planes (where the ' denotes the stacking sequence of the alternate set of atoms). Note also that the consecutive layers of the silicon and carbon atoms in the sequence for e.g., AA' is closely spaced and thus the stacking sequence can be generalized to be ABABAB… and ABCABC… in the {100}, {110} and {111} case respectively by combining the two closely spaced layers to form one plane. A B A B A B A A' B B' C C' A A' B B' C C' A B C A B C
2.3 Point Defects, Defect Migration and Annealing Behaviour 2.3.1 Introduction 7 In this section the different types of point defects in a crystal lattice are discussed. Fundamental statistics on their concentration in the lattice are presented and their diffusion mechanisms are considered. In general the diffusion behaviour of point defects in SiC cannot be fully explained yet, since it is a complex process that is still being researched. 3.2 Point Defects A point defect is defined as the insertion or absence of an atom in a crystal lattice uncharacteristic to that of the normal atomic sites. When the defect is a result of atoms comprising of the parent lattice it is termed an intrinsic defect and when the atom is an impurity it is termed extrinsic. Intrinsic point defects may further be characterised as being vacancy or interstitial, vacancy being the absence of an atom in a regular atomic site and an interstitial the insertion of an atom into a non-lattice site. This is depicted in Fig. 2.5. Fig. 2.5. The intrinsic defects, vacancy and interstitial present in a lattice (from Hull et al. (1984)) Extrinsic point defects may be characterised as substitutional, where an atom of the parent lattice lying in a lattice site is replaced by an impurity atom, or interstitial, where the impurity atom is at a non-lattice site (Fig. 2.6).
Page 1 and 2: Analysis of the Extended Defects in
Page 3 and 4: My sincere thanks to the following
Page 5 and 6: OPSOMMING Hierdie dissertasie hande
Page 7 and 8: 4.2.5. Two-Beam Scattering Matrix 4
Page 9 and 10: Dedicated to my wife and parents
Page 11 and 12: SUMMARY The dissertation focuses on
Page 13 and 14: CONTENTS Chapter 1: INTRODUCTION 1
Page 15 and 16: 1 CHAPTER ONE INTRODUCTION Silicon
Page 17 and 18: 2.1. Introduction 3 CHAPTER TWO OVE
Page 19: 2.2.2 The Zinc-Blende Structure 5 T
Page 23 and 24: v m Em vm0 exp( ) (2.2) kT 9 wher
Page 25 and 26: 11 explained and the concept of par
Page 27 and 28: 13 Straight dislocations furthermor
Page 29 and 30: 2.5 Partial Dislocations and Slip 1
Page 31 and 32: 17 Fig. 2.13. The geometrical setup
Page 33 and 34: 19 extrinsic stacking faults are th
Page 35 and 36: 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)
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59 intersection of the fault, the f
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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
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67 Fig. 6.3. Total number of displa
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7.1 Introduction 69 CHAPTER SEVEN R
Page 85 and 86:
Fig. 7.2. Simulated diffraction pat
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73 Fig. 7.3. A HRTEM image of the S
Page 89 and 90:
75 Fig. 7.5. The stacking fault sel
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(Si/ni) 2 0.000018 0.000016 0.00001
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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
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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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