期刊
NANOTECHNOLOGY
卷 31, 期 19, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1361-6528/ab6ab8
关键词
solid state dewetting; dielectric Mie resonator; micro-Raman; strain
资金
- Nano2017 FUI project
- European Union's Horizon 2020 research and innovation programme [654148 Laserlab-Europe]
- French ANR agency [ANR-15-CE24-0027-01]
- EU [828890]
- Investissements d'Avenir, a French Government program by the French National Research Agency (ANR) [ANR-11-IDEX-0001-02]
- Agence Nationale de la Recherche (ANR) [ANR-15-CE24-0027] Funding Source: Agence Nationale de la Recherche (ANR)
All-dielectric photonics is a rapidly developing field of optics and material science. The main interest at visible and near-infrared frequencies is light management using high-refractive-index Mie-resonant dielectric particles. Most work in this area of research focuses on exploiting Si-based particles. Here, we study monocrystalline Mie-resonant particles made of Ge-rich SiGe alloys with refractive index higher than that of Si. These islands are formed via solid state dewetting of SiGe flat layers by using two different processes: (i) dewetting of monocrystalline SiGe layers (60%-80% Ge content) obtained via Ge condensation of SiGe on silicon on insulator; and (ii) dewetting of a SiGe layer deposited via molecular beam epitaxy on silicon on insulator and ex situ Ge condensation, forming a Ge-rich shell surrounding a SiGe-core. Using high-spatial-resolution Raman microscopy we monitor Ge content x and strain epsilon of flat layers and SiGe-islands. We observe strain relaxation associated with formation of trading dislocations in the SiGe islands compared to the starting SiGe layers, as confirmed by TEM images. For initial high Ge concentration in the flat layers, the corresponding Ge content in the dewetted islands is lower, owing to diffusion of Si atoms from Si or SiO2 into SiGe islands. The Ge content also varies from particle to particle on the same sample. Size and shape of the dewetted particles depend on the fabrication process: thicker initial SiGe layers lead to larger particles. Samples with narrow island size distribution display rather sharp Mie resonances in the 1000-2500 nm spectral range. Larger islands display Mie resonances at longer wavelength. Positions of the resonances are in agreement with the theoretical calculations in the discrete dipole approximation.
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