Structural investigations of silicon nanostructures grown by self-organized island formation for photovoltaic applications
| Autor: | Axel Hoffmann, Andreas Schöpke, Maurizio Roczen, Martin Schade, Orman Gref, Florian Ruske, Hartmut S. Leipner, J A Töfflinger, Thomas Barthel, Enno Malguth, Gordon Callsen, Matthew R. Phillips, Lars Korte, Manfred Schmidt, Bernd Rech |
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| Rok vydání: | 2012 |
| Předmět: |
010302 applied physics
Amorphous silicon Materials science Annealing (metallurgy) Scanning electron microscope Nanotechnology 02 engineering and technology General Chemistry 021001 nanoscience & nanotechnology 01 natural sciences 7. Clean energy chemistry.chemical_compound Planar Chemical engineering chemistry 0103 physical sciences General Materials Science Wafer Nanodot Crystalline silicon Dewetting 0210 nano-technology Applied Physics |
| Zdroj: | Applied Physics A. 108:719-726 |
| ISSN: | 1432-0630 0947-8396 |
| DOI: | 10.1007/s00339-012-6956-9 |
| Popis: | The self-organized growth of crystalline silicon nanodots and their structural characteristics are investigated. For the nanodot synthesis, thin amorphous silicon (a-Si) layers with different thicknesses have been deposited onto the ultrathin (2 nm) oxidized (111) surface of Si wafers by electron beam evaporation under ultrahigh vacuum conditions. The solid phase crystallization of the initial layer is induced by a subsequent in situ annealing step at 700°C, which leads to the dewetting of the initial a-Si layer. This process results in the self-organized formation of highly crystalline Si nanodot islands. Scanning electron microscopy confirms that size, shape, and planar distribution of the nanodots depend on the thickness of the initial a-Si layer. Cross-sectional investigations reveal a single-crystalline structure of the nanodots. This characteristic is observed as long as the thickness of the initial a-Si layer remains under a certain threshold triggering coalescence. The underlying ultra-thin oxide is not structurally affected by the dewetting process. Furthermore, a method for the fabrication of close-packed stacks of nanodots is presented, in which each nanodot is covered by a 2 nm thick SiO 2 shell. The chemical composition of these ensembles exhibits an abrupt Si/SiO 2 interface with a low amount of suboxides. A minority charge carrier lifetime of 18 μs inside of the nanodots is determined. © 2012 Springer-Verlag. |
| Databáze: | OpenAIRE |
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