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50 Results 4.1 Interlayer It was shown that an aluminum oxide interlayer between the initial Al and a-Si is needed in the aluminum-induced layer exchange process [54]. The interlayer controls the velocity of the crystallization process and the nucleation density. Both, oxidation of the aluminum layer as well as the oxidation of the amorphous silicon layer in an inverse layer structure were shown to lead to a layer exchange. Still many questions concerning the interlayer need to be answered. Two fundamental questions arise regarding the role of the interface layer. ’What happens without an interface layer?’ and ’Why is an oxide layer needed?’. In order to answer the first question a sample was prepared without an interlayer, i.e. the a-Si was deposited directly onto the Al. Additionally a sample with oxide interface was prepared. The samples were annealed at 480 °C for 45 min and the Al was etched off wet chemically. SEM images without (a) and with (b) oxide layer are shown in Fig. 4.1. The samples were tilted by 30°. At the bottom of the micrographs is the glass substrate covered with silicon. In both cases the glass is covered with large compact Si islands. The sample without oxide layer shows a porous silicon structure. Through holes in the porous structure the glass substrate is visible. No continuous film is obtained. With oxide layer a continuous Si film covers the glass beneath the islands. Thus, the use of an oxide layer leads to the formation of a continuous layer. This continuous Si layer is used as substrate for the subsequent epitaxy. TEM investigations were made in order to determine the influence of the annealing process on the oxide layer. In Fig. 4.2 a TEM cross section of a sample after annealing is shown. The glass is covered by a continuous silicon layer. The top layer consist of Al with silicon islands. The presented section shows mostly silicon islands. However, top and bottom layers are clearly separated. In the inset the color-coded superposition of three electron energy loss spectroscopy (EELS) elemental maps is shown. Here, red corresponds to Al, blue to O and green to Si. Even after the layer exchange process the oxide layer is still at the interface
4.1 Interlayer 51 (a) (b) Figure 4.1: SEM micrographs of the crystallized Silicon after annealing and wet chemical removal of the Al without (a) and with (b) oxide interlayer [89]. In (a) a porous crystalline Si structure is formed. In (b) the glass substrate is covered with a continuous poly-Si film. On top of the film are Si islands which are crystalline as well.
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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 . .
Page 17 and 18: 1 Introduction ’Solar power is ho
Page 19 and 20: por deposition (PECVD) achieved par
Page 21 and 22: phous silicon interface layer is ex
Page 23 and 24: 2 State of the art This chapter giv
Page 25 and 26: 2.1 Kinetics of phase change 9 Figu
Page 27 and 28: 2.1 Kinetics of phase change 11 [e
Page 29 and 30: 2.2 Solid Phase Crystallization (SP
Page 31 and 32: 2.2 Solid Phase Crystallization (SP
Page 33 and 34: 2.3 Metal-Induced Crystallization (
Page 39 and 40: 2.4 Aluminum-Induced Layer Exchange
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: 4 Results In order to understand an
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 and 96: 4.2 Temperature profiles 79 R C [%
Page 97 and 98: 4.2 Temperature profiles 81 a small
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
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5.1 Definition of three crucial Si
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5.2 The ALILE process in the phase
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5.2 The ALILE process in the phase
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5.3 Depletion regions in the ALILE
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5.4 Comparison of the qualitative m
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5.5 Preferential orientation model
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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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(a) 100 µm - Helmholtz-Zentrum Berlin

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