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

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84 These results agree well with the theories proposed by Gao et al. (2001) and Perlado et al.(2000) from their molecular dynamics simulations of displacement cascades in SiC. It shows that the proton does not impart to the lattice enough energy to create vast displacement cascades capable of creating an amorphous region. This is due to its small mass compared to the constituent atoms and also due to the high threshold displacement energies of the atoms, especially the Si. The anisotropy of the displacement energies between the constituent atoms also play a big role and their difference in recovery after the thermal spike prevents large defect clusters to form during the radiation process. It also causes the cascade to be dispersed, containing only single point defects and small point defect clusters. Finally the results also show that a significantly higher proton dose should be used if any form of visible radiation damage is to be produced. 7.3.2 Annealed at 1300°C No evidence of radiation damage was observed after a 1hr anneal at 1300°C. Bright- field TEM images using all the reflections 200, 111, 220 and 311 showed no significant changes in the characteristics observed in the unimplanted or implanted unannealed samples. Fig. 7.13. shows a bright field TEM image of the sample using a 311 two-beam condition. This image is similar to that obtained with other two-beam conditions. Only thin twins, edge-on stacking faults and inclined stacking faults were seen and no damage region or dislocation loops due to the clustering of point defects were observed.
85 Fig. 7.13. Bright-field TEM micrograph of 3C-SiC sample annealed at 1300°C for 1 hr. B = [011], g = 311, s ≥ 0. The insert is a SAD pattern of the two beam condition used. 7.3.3 Annealed at 1600°C For the analysis of this sample a beam direction was used since the sample was most electron transparent in this direction. Also it was assumed that if the effects of radiation damage was to be seen in the sample it would be in the form of dislocation loops which would lie on the {111} close packed planes. These loops will be strongly visible using 220 type reflections which in turn are easily accessible using a beam direction. However extensive examination of the sample using all of the 220 reflections showed no evidence of a damage region or dislocation loops having formed due to the clustering of intrinsic point defects. The only defects found were stacking faults with their associated partial dislocations and interesting dislocation complexes such as shown in Fig. 7.14.
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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
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23 Fig. 2.20. The process of vacanc
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S n Td (3.2) 25 and is also referr
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27 where a = a0(Z1 2/3 + Z2 2/3 ) -
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29 Using this expression, curves of
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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: 83 Fig. 7.12 which was obtained by
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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