Nature provides a variety of micro and nano structures which can be used as templates for manufacturing photonic sensing surfaces. For example, surfaces replicated from the wings of certain butterfly species can absorb or reflect light over a given spectral range .
Nowadays, nanotechnology and biomimetic technology make it possible to obtain a single replica , but the challenge is to carry out high throughput, cost-effective replication of such surfaces for practical applications. In this paper, we deposit a layer of Al2O3 on the surface of the butterfly wings by low temperature atomic layer deposition (ALD). The alumina coated wing is used as a mold to imprint butterfly wing pattern on poly(methylmethacrylate) (PMMA) on the surface of a SiO2/Si-wafer stack by nanoimprint lithography. The SiO2 layer is then etched down to the Si wafer using the imprinted PMMA layer as a mask. In such a way, we can obtain a stable and hard SiO2 mold, which can be used to produce in large number the butterfly wing patterns on Si substrates for improving their light absorption and carrier collection ability .
Recently, it was reported that Si solar cells with the Al2O3 coating show a high-efficiency . We investigate the optical and electrical properties of the low-temperature ALD Al2O3 layer. According to the flat-band voltage ΔV extracted from the high frequency C-V curve, we also estimate the negative charge density in the Al2O3 layer to be 3 x 1012 /cm2, which will provide an effective field-effect passivation for reducing the surface recombination of the minority carriers. These results demonstrates large potential on applying the replicated butterfly wing patterns on Si wafer with the Al2O3 coating for photovoltaic applications with high antireflection and lower combination properties.
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Co-authored by X. Tang (a), L. A. Francis (a), P. Simonis (b), M. Haslinger (a), R. Delamare (a), O. Deschaume (c), D. Flandre (a), P. Defrance (c), A. M. Jonas (c), J.- P. Vigneron (b), and J.-P. Raskin (a)
(a) ICTEAM institute, Université catholique de Louvain, Place du Levant 3, 1348 Louvain-la-Neuve, Belgium.
(b) Départment de Physique, Facultés Universitaires Notre-Dame de la Paix, Belgium
(c) IMCN institute, Université catholique de Louvain, Belgium
Presented at the 11th International Conference on Atomic Layer Deposition, June 26th-29th, 2011, Boston, MA.
Corresponding author: L. A. Francis, laurent (dot) francis (at) uclouvain (dot) be.