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

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16 2.6 Dislocations in the Zinc-Blende Structure As in fcc metals, slip occurs in the zinc blende structure on close packed planes along close packed directions. The predominant slip system is {111} with the majority of dislocations lying along and directions. The asymmetry in the zinc-blende lattice causes two possible dislocations in the lattice for identical Burgers vector and dislocation line direction. As discussed earlier the {111} layers consist of sets of closely spaced double layers of the constituent atoms with small internal spacing a 3a and large external spacing of . The glide 4 3 4 of a dislocation can then either cut through the small internal spacing or large external spacing. Two sets of dislocations are thus generated depending on the glide system. The set of dislocations causing slip between the closest spaced layers is called the glide set while the other called the shuffle set. The shuffle set is commonly assumed to be the correct description since fewer bonds have to be broken for the dislocations to move across the {111} planes. The properties of dislocations in the zinc-blende structure may be explained in terms of the concept of a 60° dislocation. In this configuration the slip plane is of the {111} type with the dislocation line and Burgers vector making an angle of 60° with one another. This is illustrated in Fig. 2.13.
17 Fig. 2.13. The geometrical setup of the sixty degree dislocation in a zinc-blende crystal lattice (from Stirland et al. (1976)) There are three possible sixty degree dislocations that could lie on one {111} plane. The core of the dislocation contains atoms with broken bonds and the axis of the dislocation lies along a set of identical type atoms. If GaAs is used as an example, the broken bonds may belong to either Ga or As atoms. The dislocations are called an α and β dislocation respectively depending on whether the broken bonds belong to Ga or As atoms respectively. This situation is illustrated in Fig. 2.14. Fig. 2.14. The (a) α and (b) β type sixty degree dislocations in a zinc-blende crystal lattice (from Stirland et al. (1976))
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 and 20: 2.2.2 The Zinc-Blende Structure 5 T
Page 21 and 22: 2.3 Point Defects, Defect Migration
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: 2.5 Partial Dislocations and Slip 1
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)
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
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67 Fig. 6.3. Total number of displa
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7.1 Introduction 69 CHAPTER SEVEN R
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Fig. 7.2. Simulated diffraction pat
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73 Fig. 7.3. A HRTEM image of the S
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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
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81 Fig. 7.11. Bright field TEM micr
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83 Fig. 7.12 which was obtained by
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85 Fig. 7.13. Bright-field TEM micr
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87 (a) (b) Fig. 7.15. The (a) exper
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89 In the following paragraphs the
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Fig. 7.18. CBED pattern taken of th
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93 Table 7.5. The measured paramete
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7.4.2 Results 95 Fig. 7.22. Bright-
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97 Twin platelets on {111} planes
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99 REFERENCES Blumenau, A.T., Jones
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101 Hull, D., Bacon, D.J. : (1984)
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103 Smith, D.J., Jepps, N.W. and Pa
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