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

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7.2.3 Twinning Fig. 7.12. Bright-field TEM micrograph of a twinned area in the 3C- SiC lattice. B = [011], g = 82 _ 11 1, s ≥ 0. The insert is a SAD pattern of the area with the corresponding dark-field micrograph obtained using the twin spot indicated Fig. 7.12. shows a bright-field TEM image of an area close to the SiC/Si interface in the SiC where twins are present. The twins were identified by analysing the extra spots in the SAD pattern shown in Fig. 7.12. The extra spots are consistent with a 180° rotation of the lattice about a {111} plane. Also the dark-field image shown in
83 Fig. 7.12 which was obtained by using one of the extra spots showed an inversion of the contrast over the area indicating the twinned regions. The twins are long, very narrow, originate at the interface and extent only a short distance into the bulk of the material from the interface. The presence of twins is consistent with the theories of nucleation and growth and accommodation of lattice misfit presented in Sections 5.2. and 5.3.2. The twins are most probably introduced during the growth process. Since the film/substrate interfacial energies of the twinned nuclei is higher than that of the epitaxial ones the epitaxial ones will have a faster lateral growth than the twinned nuclei and will also cause the twins to grow along inclined {111} planes. This is exactly what is seen in results and supports the theory presented in Sections 5.2 and 5.3.2. 7.3 Hydrogen Implanted -SiC In this section the results of the investigation of proton irradiated 3C-SiC to a dose of 2.8 × 10 16 protons/cm 2 at 400 keV are presented. Implanted samples that were unannealed and annealed at 1300 °C and 1600°C for one hour were prepared in cross- section and analysed by TEM. In the unannealed sample no noticeable change in the microstructure of the SiC was seen showing the same characteristics of the unimplanted SiC sample. Also no effect due to implantation was seen in any of the annealed samples. No evidence of a damage region was seen or of defects having formed as a result of the irradiation process. The structure of the SiC remained crystalline with the cubic 3C phase for every sample even those annealed at 1600°C. 7.3.1 Unannealed The unannealed sample yielded no difference from the characteristics seen in the unimplanted sample. No evidence of radiation damage or a damage zone was seen with the SiC remaining crystalline throughout. The main defects seen were stacking faults with their associated partial dislocations and twins originating from the interface and extending only a limited distance into the bulk of the SiC layer.
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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
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: 81 Fig. 7.11. Bright field TEM micr
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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