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

More documents

Recommendations

Info

32 Thus if E * >Ed all Rutherford collisions displace atoms, but an energy LB exist above which only some of the Rutherford collisions do so. LB is given by, L B 2 ER 2 2 2 3 2 3 M 2 4 Z1 Z 2 ( Z1 Z 2 )( ) (3.21) E M d 1 Thus to summarize at higher energies the ion undergoes Rutherford collisions and in some cases atoms are displaced. If the energy falls below LB all Rutherford collisions displace atoms. The reason why only some Rutherford collisions displace atoms at energies E>>LB is since half the energy lost to atoms which receive energy less than Ed and are thus not displaced. This energy loss is dissipated through lattice vibrations termed thermal spikes. As the energy of the ion decreases further the importance of energy loss due to hard- sphere collisions become more important than that of electronic energy loss and for this reason Kinchin and Pease (1955) defined a transition energy LC. It is a defined as the energy above which all energy loss is due to electronic excitation and below which is due to hard-sphere collisions. The value of LC is difficult to obtain in general but is approximated for insulators as, 1 M LC E m 4 e G (3.22) where ΔEG is the band gap between valence and conduction band, me electron mass. For metals the relation is, 1 M LC m 4 e f where εf is the Fermi level but in general LC may be approximated by, (3.23) LC A keV (3.24)
33 where A is the atomic weight. Thus in general it is found that the number of atoms displaced by an incoming ion Nd depends firstly on its energy. If its energy is less than LC the number of displaced atoms is determined as follows. Consider an atom with initial energy T < LC moving in a solid. The first collision then results in a sharing of the energy T with the struck atom which on average is half that of T. Both atoms will then continue with energy 1/2T and collide with one atom each sharing their energy with the struck atom with a factor of an half on average. This process will continue until the average energy of the struck atoms falls below 2Ed and if this occurs after q groups of collisions the total amount of displaced atoms will be given by, q N d 2 ( T 2Ed ) (3.25) This expression is valid if T is greater than 2Ed, if T is between Ed and 2Ed only one atom is displaced and below Ed obviously no atom is displaced. If T is bigger than LC the expression becomes LC/2Ed. If the energy of the atom is bigger than LC and LB Kinchin and Pease showed that the moving atom will displace ΔN atoms in losing energy ΔE, where N P E E (3.26) and P is given by, d meZ 1[ 1 ln( E 2Ed ] P (3.27) 2 4M ( Z / Z) ln( 4m E / M I ) 1 effective 4M M 1 2 with and 2 2 ( M 1 M 2 ) ion is light the expression may be simplified to, N d P E LC ) bL Ed e 2 I 8. 8Z the mean ionization potential. If the implanted ( 0 C (3.28)
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 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: 31 As stated previously hard-sphere
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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?