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

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My sincere thanks to the following people: ACKNOWLEDGEMENTS - My supervisor, Professor J.H. Neethling for his guidance and encouragement throughout this project. - Any of the staff or students from the NMMU Physics Department whom played a contributing role in any way during my research - SANHARP for their financial assistance - My parents, brother and sister for encouragement and support throughout - My wife for her understanding, support and love The assistance of the following people is also gratefully acknowledged: - Dr Anna Carlsson at FEI Company in Eindhoven for the HRTEM results - Dr Chris Franklyn at NECSA for doing the proton implantation - NovaSiC for supplying the SiC used in the study - Johan Westraadt for the annealing of the samples at the University of the Witwatersrand
SUMMARY The dissertation focuses on the analysis of the extended defects present in as-grown and proton bombarded β-SiC (annealed and unannealed) grown by chemical vapour deposition (CVD) on (001) Si. The proton irradiation was done to a dose of 2.8 × 10 16 protons/cm 2 and the annealing took place at 1300°C and 1600°C for 1hr. The main techniques used for the analysis were transmission electron microscopy (TEM) and high resolution TEM (HRTEM). From the diffraction study of the material the phase of the SiC was confirmed to be the cubic beta phase with the zinc-blende structure. The main defects found in the β- SiC were stacking faults (SFs) with their associated partial dislocations and microtwins. The SFs were uniformly distributed throughout the foil. The SFs were identified as having a fault vector of the type 1/3 with bonding partial dislocations of the type 1/6 by using image simulation. The SFs were also found to be predominantly extrinsic in nature by using HRTEM analysis of SFs viewed edge-on. Also both bright and dar-field images of SFs on inclined planes exhibited symmetrical and complementary fringe contrast images. This is a result of the anomalous absorption ratio of SiC lying between that of Si and diamond. The analysis of the annealed and unannealed irradiated β-SiC yielded no evidence of radiation damage or change in the crystal structure of the β-SiC. This confirmed that β-SiC is a radiation resistant material. The critical proton dose for the creation of small dislocation loops seems to be higher than for other compound semiconductors with the zinc-blende structure.
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: Dedicated to my wife and parents
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 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)
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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