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

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6.5 Sample Preparation 68 For the analysis in the TEM, samples were prepared in cross-section as illustrated in Fig.6.4. Two sections with dimensions 3mm by 0.5 mm were cut from the irradiated area of the SiC samples. The two sections were then glued together using an epoxy solution with the faces of the irradiated surfaces facing towards one another. Following this two sections of the same dimensions as before of Si were cut and glued to either side of the SiC sections for extra support. The samples were then mechanically thinned to approximately 250 µm by means of wet sandpapering followed by polishing on a rotating pad using a 3 µm diamond grit solution to remove any residual surface damage from the sandpapering. This was then mounted on a copper microscope grid using an epoxy solution with the polished face on the grid. The other side of the sample was polished using the same procedure as before to a total thickness of approximately 50 µm. The samples were finally milled using a Gatan PIPS (Precision Ion Polishing System) by means of the simultaneous bombardment of the top and bottom surfaces with 5 kV argon-ion beams at an incident angle of 6°. The milling continued until a small hole appeared in the sample. Fig. 6.4. Schematic representation of the steps in the preparation of a (110) cross- sectional sample (Neethling (1980)).
7.1 Introduction 69 CHAPTER SEVEN RESULTS AND DISCUSSION The following chapter contains the results obtained from a TEM investigation of the as-grown and ion bombarded 3C-SiC. The results of this investigation are also compared with findings of other researchers. 7.2 Extended Defects in -SiC Grown by CDV on (001) Si A cross-sectional sample of 3C-SiC grown on Si by CVD was prepared using the technique described in Section 6.5. Following this an investigation was done by using transmission electron microscopy (TEM) as well as high-resolution TEM (HRTEM). From these results the phase of the SiC was determined to be the cubic (3C-SiC) zinc- blende structure with a lattice parameter of 4.35Å . The interface between the SiC and Si was also investigated. It was found from diffraction data that parallel epitaxial orientation between the two materials was obtained during growth. The consistency along the interface was also investigated and it was seen to contain a reasonable amount of inhomogeneities. Examples of very thin twinned sections originating at the interface were also found. In the bulk of the material a large density of stacking faults was observed lying on the {111} close-packed planes with bonding partials of the 1/6 type. The stacking faults observed in an edge-on orientation showed an interesting feature in that they generate satellite streaks in a diffraction pattern. This is consistent with what is normally seen in materials containing narrow planar precipitates. This is due to the shape of the precipitate being similar to that of a plate like crystal (see p.97 Hirsch et al. (1965)). Furthermore these stacking faults were investigated using HRTEM and found to be extrinsic in nature. These findings agree with that found by previous researchers (Sections 5.2-5.3).
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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
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: 67 Fig. 6.3. Total number of displa
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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