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

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14 Dislocation glide takes place on the slip plane which is the {111} for fcc and zinc blende structures and is a result of atoms above and below the plane being displaced by b with respect to one another. Fig. 2.10. A representation of the process of glide in a crystal (from Bollmann (1970)) If a dislocation climbs it moves perpendicular to the glide plane. It is only possible if the dislocation has an edge component and if the temperature and stress is sufficient for diffusion to be possible. Fig. 2.11. A representation of the process of climb in a crystal (from Bollmann (1970)) In general glide is the only mechanism present at low temperatures during plastic deformation. Also from these mechanisms the definition of the slip plane may be made. It is defined as the plane which contains both the dislocation line and Burgers vector of the dislocation.
2.5 Partial Dislocations and Slip 15 In the fcc structure slip occurs on the close-packed planes {111} with the slip direction . Slip involves the sliding of close-packed planes of atoms over each other. To see how this can occur the following may be done. Consider that the close- packed planes can be simulated by a set of hard spheres. Fig. 2.12. The simulation of close-packed planes by a set of hard spheres to describe the concept of slip in a crystal lattice (from Hull et al. (1984)) The full circles represents the A layer, the sites marked B the B layer and C the C layer. Consider next the movement of the layers when they are sheared over each other. It will be found that that the B layer of atoms will first move to the nearby C site and then to the next B site instead of directly moving from B site to B site. Thus the unit lattice displacement b1 is achieved by two movements about the C positions represented by b2 and b3. If one considers the movement of the unit 1/2 dislocation in the fcc lattice it implies that the motion will take place via two dislocations termed partial dislocations with Burgers vectors b2 and b3 in a reaction of the type, 1 2 110 1 1 211 121 6 6 (2.6) This occurs since it is energetically favourable for the edge dislocation to dissociate according to Frank’s rule with b 2 edge = a 2 /2 which is greater than bp1 2 + bp2 2 = a 2 /3.
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: 13 Straight dislocations furthermor
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)
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 and 88:
73 Fig. 7.3. A HRTEM image of the S
Page 89 and 90:
75 Fig. 7.5. The stacking fault sel
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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