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5.2 Change in Si-C stretching mode frequency with carbon content 96 5.3 Integrated absorption of Si-C stretching mode versus carbon content 97 5.4 Variation of Urbach energy and edge width parameter B with carbon content in the fUm 99 5.5 Variation of (a) ESR spin density (b) g-value with carbon content 101 5.6 Normalized CW PL spectra of a-Sii_xCr:H films for various values of x at 25 K 103 5.7 Change in peak energy(EL) a-iiti the bandwidth(A£^L) of the CW spectra with carbon content in the fUm 105 5.8 Bandwidth of the CW spectra versus Urbach energy of the samples 5.9 Comparison of PL decays at 1.46 eV for various values of x at 25 K 5.10 Comparison of deconvoluted PL decays at 1.46 eV 5.11 Comparison of Ufetime distributions at 1.46 eV 5.12 Variation in the relative contributions of the three lifetimes to the PL decay at 1.46 eV with carbon content at 25 K 113 5.13 Comparison of deconvoluted PL decays at a thermalization depth of ~ 0.3 eV 116 5.14 Comparison of lifetime distributions at same thermalization depth 117 5.15 Comparison of lifetime distributions at different emission energies for sample C5 118 6.1 Variation of optical gap with nitrogen content 130 6.2 Change in Urbach energy and the edge width parameter with nitrogen content 131 6.3 Defect density versus nitrogen content 133 6.4 Comparison of CW PL spectra for films with different nitrogen content 13^ 6.5 Change in PL peak energy and PL bandwidth with nitrogen content 135 6.6 Correlation between CW PL bandwidth and Urbach energy 13( VI
6.7 Comparison of decays for different nitrogen contents at 1.46 eV 13i 6.8 Comparison of lifetime distributions for samples NFl, NF4 and NF5 14i 7.1 Variation of PL and PC with temperature 14 7.2 Comparison of un-normalized CW PL spectra with and without electric field at 100 K 14( 7.3 Comparison of normalizedCW PL spectra with and without electric field at 100 K 14: 7.4 --^ versus Electric Field 7.5 PC versus Electric Field 7.6 „ ^fn\ versus Electric Field 7.7 ; ^ versus--^
Page 1 and 2: PHOTOLUMINESCENCE STUDIES IN HYDROG
Page 3 and 4: V. PHOTOLUMINESCENCE IN a-Sii_xCx:H
Page 5: LIST OF FIGURES 1.1 Comparison of a
Page 9 and 10: different from those in c-Si. Thus
Page 11 and 12: 11 (*) Photoluminescence 10^ J3 rz
Page 13 and 14: (a) -*-ao-^ Crystalline 00 c Hi 'JK
Page 15 and 16: 8 wavefunction of extended and loca
Page 17 and 18: Figure 1.4: Schematic of density of
Page 19 and 20: 12 10'- 'v, 10 10 > Thermalization
Page 21 and 22: 14 energy turns out to be 10^ cm~^
Page 23 and 24: 16 1.1.4.1 Radiative TunneUng Since
Page 25 and 26: 18 Since doping introduces addition
Page 27 and 28: 20 1 - /?c = 100 A V) C 10-' u c u
Page 29 and 30: 22 where M is the matrix element of
Page 31 and 32: 24 10* .^10* C It Temperature 12 K
Page 33 and 34: 26 the temporal resolution needed t
Page 35 and 36: 28 temperature, excitation energy,
Page 37 and 38: CHAPTER n EXPERIMENTAL DETAILS 2.1
Page 39 and 40: 32 Table 2.1: Deposition parameters
Page 41 and 42: 34 In all cases, the films were dep
Page 43 and 44: 36 2.2.2 Constant Photocurrent Meth
Page 45 and 46: 38 alloys of a-Si:H. The shift in t
Page 47 and 48: 40 dye laser pulse is typically 500
Page 49 and 50: 42 The rise time of this tube is ~
Page 51 and 52: CHAPTER in DATA ANALYSIS 3.1 Calibr
Page 53 and 54: 46 in CM o cs CO ^-» c D ^ h— CD
Page 55 and 56: 48 the decay parameters obtained fr
Page 57 and 58:
50 where a, and r, are the zero-tim
Page 59 and 60:
52 U3 CO »^7 O tn - 0.0 10.0 20.0
Page 61 and 62:
54 lifetime distribution. This sugg
Page 63 and 64:
56 separately because, according to
Page 65 and 66:
58 Table 4.1: Summary of characteri
Page 67 and 68:
60 1.1 1.2 1.3 1.4 Energy (eV) Figu
Page 69 and 70:
62 chapter, the total contribution
Page 71 and 72:
64 in d o At 1.46 eV c O _SCD o CJ
Page 73 and 74:
66 As the Fermi level lies somewher
Page 75 and 76:
68 of these states as a function of
Page 77 and 78:
70 thermalization depth of electron
Page 79 and 80:
72 Ennission Energy 1.40 eV 1.46 eV
Page 81 and 82:
ecombination decreases (according t
Page 83 and 84:
76 CO 00 3d- 0) E *a5S M_ O- "^ d o
Page 85 and 86:
78 Although the three mean lifetime
Page 87 and 88:
80 where E is the energy of the exc
Page 89 and 90:
82 relative contribution of the lon
Page 91 and 92:
84 4.2.5 Electric Field Dependence
Page 93 and 94:
86 approximation, they model the PL
Page 95 and 96:
88 more plausible with one major mo
Page 97 and 98:
90 comparable lifetimes and a const
Page 99 and 100:
CHAPTER V PHOTOLUMINESCENCE IN a-Si
Page 101 and 102:
94 Table 5.1: Carbon Contents of th
Page 103 and 104:
96 0.0 0.2 0.4 Composition(x) Figur
Page 105 and 106:
98 integrated absorption follows th
Page 107 and 108:
100 energy increases monotonically
Page 109 and 110:
102 content (Fig. 5.5(b)) to almost
Page 111 and 112:
104 carbon content are shown in Fig
Page 113 and 114:
106 Li this equation, if we assume
Page 115 and 116:
108 indicating a disorder broadenin
Page 117 and 118:
110 the foUowing discussion we wiU
Page 119 and 120:
112 in d o ai At 25K LEGEND • x=0
Page 121 and 122:
114 Table 5.2: Comparison of ao for
Page 123 and 124:
116 0.0 10.0 20.0 30.0 40.0 50.0 Ti
Page 125 and 126:
118 in O in in oi x=0.99 • At 1.6
Page 127 and 128:
120 PL decay at similar emission en
Page 129 and 130:
122 needed to affect PL decays in t
Page 131 and 132:
124 Siebert et al. [70] have found
Page 133 and 134:
CHAPTER VI PHOTOLUMINESCENCE IN a-S
Page 135 and 136:
128 Table 6.1: Correlation between
Page 137 and 138:
130 0.00 0.03 0.06 0.09 Composition
Page 139 and 140:
132 measurements shows a continuous
Page 141 and 142:
134 CM d LEGEND x=0.00 x=0.05 'x=0.
Page 143 and 144:
136 0.04 0.08 0.12 Urbach Energy(eV
Page 145 and 146:
138 O o o CD O o GO CM x=0.00 x=0.0
Page 147 and 148:
140 LEGEND x=0.05 x=^o:io • x=0.1
Page 149 and 150:
142 Another possibility for the ins
Page 151 and 152:
14-1 f 1.00 'co 4—» 'E Zj CD d-
Page 153 and 154:
146 O d in O d CO • ^M^ c 3 x> ^
Page 155 and 156:
148 discussion we wiU use --^ for c
Page 157 and 158:
150 10 10* Field{V/cm) Figure 7.5:
Page 159 and 160:
152 0.1 0.2 0.3 0.4 Relative Change
Page 161 and 162:
154 The two curves exhibit a linear
Page 163 and 164:
156 IpL (T=25 K,F=0). In the region
Page 165 and 166:
and 158 j~r - 1 a r^ T < 100 K. (7.
Page 167 and 168:
160 Thus, these two quantities are
Page 169 and 170:
162 We think that this argument hol
Page 171 and 172:
CHAPTER Vm CONCLUSIONS In this work
Page 173 and 174:
166 This supports the disorder broa
Page 175 and 176:
168 prepared a-Sii_xCx:H fUms and c
Page 177 and 178:
REFERENCES [1] Carison, D.E., and W
Page 179 and 180:
172 [36] Tauc, J., Grigorovici, R.
Page 181 and 182:
174 [71] Palsule, C, Gangopadhyay,
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