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80 Results -2 ] N G ,F [1 0 3 m m 8 6 4 2 �� H S 1 �� 0 0 3 0 6 0 9 0 1 2 0 1 5 0 � �� Figure 4.24: Average final grain density NG,F vs. process time tP for experiment HS1. The corresponding step times are indicated. The reference curves have been interpreted as tS = 0 min (500 °C) and tS = 150 min (460 °C). NG,F decreases strongly for tS between 40 min and 80 min. In Fig. 4.24 NG,F is shown versus the process time tP (time at RC = 95 %) for experiment HS1 together with the corresponding step times tS. The final nucleation density NG,F is strongly modified by tS. Increasing the temperature from 460 °C to 500 °C after 40 min does not lead to a major change in NG,F compared with the isothermal anneal at 500 °C (tS = 0 min). Between tS = 40 min and tS = 80 min increasing tS results in a strong reduction of NG,F . Whereas for times above 80 min no further change can be observed. This means that upon reaching a certain annealing time tA the annealing temperature can be increased without any new nucleation. Thus the grain size remains the same but the process time is re- duced. The initial goal of the heating step approach has been reached successfully even with a single temperature step. It is believed that an annealing temperature limit exists to which the sample can be heated at any time without additional nucleation. The time evolution of this annealing temperature limit is unclear. In order to investigate the behavior more closely a further specimen prepared with the same deposition parameters as the specimen before has been annealed with
4.2 Temperature profiles 81 a smaller increment in step time and step temperature. It was found that for this specimen the decrease in NG,F took place already at a shorter step time of 30 min to 50 min instead of 40 min to 80 min as for the specimen examined above. In the experiments both step temperature TS and step time tS were varied in order to de- termine the course of the annealing temperature limit. Thus, various step time and step temperature couples from tS = [30, 35, 40, 50 min] and TS = [5, 10, 15, 20, 25 °C] were chosen. In Fig. 4.25 the difference between NG,F and NG,S, i.e. the additional average nucleation density, is shown versus the average grain size dG,S at the step time tS. It can clearly be seen in the figure that upon reaching an average grain size at tS of about dG,S = 5.5 µm no further nucleation occurs. This behavior is independent of the step temperature (not shown here). However, when the average grain size dG,S at tS is below 5.5 µm new nucleation takes place depending on the step temperature TS. Higher TS are accompanied by an increase of the nucleation (not shown in Fig. 4.25). The average final grain density does not ex- ceed NG,F = 3.7 · 10 3 mm −2 in case of dG,S > 5.5 µm. Thus the maximum final grain size that can be reached is about dG,F = 16.5 µm (dG,F = (1/NG,F ) 1/2 with NG,F = 3.7 · 10 3 mm −2 ). This observation can be interpreted as follows. At the step time tS there exists a zone of dZ = 5.5 µm (at dG,S = 5.5 µm) on each side of the grain where no new nucleation (dG,F = dG,S + 2dZ) takes place (Fig. 4.26). Once these zones overlap the temperature can be increased to higher values and still now new grains nucleate. This is a first experimental proof for the depletion regions responsible for the suppression of nucleation suggested by Nast et al. [52]. The goal of the heating step experiments was to reduce the process time without increasing the nucleation density. This goal was achieved. An estimated grain size limit was found at which the annealing temperature could be increased without new nucleation. This is a first proof for the depletion regions being responsible for the nucleation suppression. With increasing the annealing temperature after the critical grain size is reached the grain growth velocity can be increased strongly and thus the process time is decreased without further nucleation.
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Nucleation and growth during the fo
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"Our ignorance is not so vast as ou
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Zusammenfassung Dünne Schichten au
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• Temperatureprofile mit hoher En
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3.2 In-situ optical microscopy . .
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1 Introduction ’Solar power is ho
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por deposition (PECVD) achieved par
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phous silicon interface layer is ex
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2 State of the art This chapter giv
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2.1 Kinetics of phase change 9 Figu
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2.1 Kinetics of phase change 11 [e
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2.2 Solid Phase Crystallization (SP
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2.2 Solid Phase Crystallization (SP
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2.3 Metal-Induced Crystallization (
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2.4 Aluminum-Induced Layer Exchange
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Page 45 and 46: 2.5 Current research involving ALIL
Page 53 and 54: 3 Experimental This thesis is focus
Page 55 and 56: 3.1 Sample preparation 39 does not
Page 57 and 58: 3.1 Sample preparation 41 � �
Page 59 and 60: 3.2 In-situ optical microscopy 43 m
Page 61 and 62: 3.2 In-situ optical microscopy 45 B
Page 63 and 64: 3.3 Electron Back Scatter Diffracti
Page 65 and 66: 4 Results In order to understand an
Page 67 and 68: 4.1 Interlayer 51 (a) (b) Figure 4.
Page 69 and 70: 4.1 Interlayer 53 Figure 4.2: TEM c
Page 71 and 72: 4.1 Interlayer 55 c o u n ts [a .u
Page 73 and 74: 4.1 Interlayer 57 R C [% ] 1 0 0 8
Page 75 and 76: 4.1 Interlayer 59 � � ��
Page 77 and 78: 4.1 Interlayer 61 � � ��
Page 79 and 80: 4.1 Interlayer 63 -2 ] N G [m m 8 6
Page 81 and 82: 4.1 Interlayer 65 TA = 450 °C TA =
Page 83 and 84: 4.1 Interlayer 67 (111) (100) (110)
Page 85 and 86: 4.1 Interlayer 69 4.1.2 Molybdenum
Page 87 and 88: 4.1 Interlayer 71 Fig. 4.17 optical
Page 89 and 90: 4.1 Interlayer 73 R C [% ] 1 0 0 8
Page 91 and 92: 4.2 Temperature profiles 75 face la
Page 93 and 94: 4.2 Temperature profiles 77 � �
Page 95: 4.2 Temperature profiles 79 R C [%
Page 99 and 100: 4.2 Temperature profiles 83 � �
Page 101 and 102: 4.2 Temperature profiles 85 (a) (b)
Page 107 and 108: 4.2 Temperature profiles 91 ��
Page 109 and 110: 4.2 Temperature profiles 93 in. Thu
Page 111 and 112: 4.2 Temperature profiles 95 ��
Page 113 and 114: 5 Discussion Two of the most import
Page 115 and 116: 5.1 Definition of three crucial Si
Page 125 and 126: 5.2 The ALILE process in the phase
Page 127 and 128: 5.2 The ALILE process in the phase
Page 129 and 130: 5.3 Depletion regions in the ALILE
Page 131 and 132: 5.4 Comparison of the qualitative m
Page 137 and 138: 5.5 Preferential orientation model
Page 145 and 146: 6 Conclusions In the aluminum-induc
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A Preferential orientation calculat
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The area of the base of the pyramid
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B Abbreviations, symbols and units
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symbol unit meaning ∆G a eV activ
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Bibliography [1] M. Rogol, S. Doi,
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[20] R.W. Bower, R. Baron, J.W. May
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[38] J. Jang, J.Y. Oh, S.K. Kim, Y.
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[58] N.-P. Harder, T. Puzzer, P. Wi
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[72] G. Ekanayake, S. Summers, and
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[87] H.R. Philipp and E.A. Taft. An
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list of publications journal papers
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B. Rau, J. Klein, J. Schneider, E.
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(2002), 87. S. Gall, M. Muske, I. S
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tion. Special thank’s go to Dr. M
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10/95-09/98 student electrical engi
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