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We report on the unconventional optical properties exhibited by a two-dimensional array of thin Si nanowires arranged in a random fractal geometry and fabricated using an inexpensive, fast and maskless process compatible with Si technology. The structure allows for a high light-trapping efficiency across the entire visible range, attaining total reflectance values as low as 0.1% when the wavelength in the medium matches the length scale of maximum heterogeneity in the system. We show that the random fractal structure of our nanowire array is responsible for a strong in-plane multiple scattering, which is related to the material refractive index fluctuations and leads to a greatly enhanced Raman scattering and a bright photoluminescence. These strong emissions are correlated on all length scales according to the refractive index fluctuations. The relevance and the perspectives of the reported results are discussed …
Nature Publishing Group
Publication date: 
1 Apr 2016

Barbara Fazio, Pietro Artoni, Maria Antonia Iatì, Cristiano D'andrea, Maria Josè Lo Faro, Salvatore Del Sorbo, Stefano Pirotta, Pietro Giuseppe Gucciardi, Paolo Musumeci, Cirino Salvatore Vasi, Rosalba Saija, Matteo Galli, Francesco Priolo, Alessia Irrera

Biblio References: 
Volume: 5 Issue: 4 Pages: e16062-e16062
Light: Science & Applications