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Subwavelength-sized dielectric Mie resonators have recently emerged as a promising photonic platform, as they combine the advantages of dielectric microstructures and metallic nanoparticles supporting surface plasmon polaritons. Here, we report the capabilities of a dewetting-based process, independent of the sample size, to fabricate Si-based resonators over large scales starting from commercial silicon-on-insulator (SOI) substrates. Spontaneous dewetting is shown to allow the production of monocrystalline Mie-resonators that feature two resonant modes in the visible spectrum, as observed in confocal scattering spectroscopy. Homogeneous scattering responses and improved spatial ordering of the Si-based resonators are observed when dewetting is assisted by electron beam lithography. Finally, exploiting different thermal agglomeration regimes, we highlight the versatility of this technique, which, when assisted by focused ion beam nanopatterning, produces monocrystalline nanocrystals with ad hoc size, position, and organization in complex multimers.

Si-based nanoarchitectures are formed with unprecedented precision and reproducibility via templated dewetting of thin SOI.

The extraordinary properties of graphene have spurred huge interest in the experimental realization of a two-dimensional honeycomb lattice of silicon, namely, silicene. However, its synthesis on supporting substrates remains a challenging issue. Recently, strong doubts against the possibility of synthesizing silicene on metallic substrates have been brought forward because of the non-negligible interaction between silicon and metal atoms. To solve the growth problems, we directly deposited silicon on a chemically inert graphite substrate at room temperature. Based on atomic force microscopy, scanning tunneling microscopy, and ab initio molecular dynamics simulations, we reveal the growth of silicon nanosheets where the substrate-silicon interaction is minimized. Scanning tunneling microscopy measurements clearly display the atomically resolved unit cell and the small buckling of the silicene honeycomb structure. Similar to the carbon atoms in graphene, each of the silicon atoms has three nearest and six second nearest neighbors, thus demonstrating its dominant sp configuration. Our scanning tunneling spectroscopy investigations confirm the metallic character of the deposited silicene, in excellent agreement with our band structure calculations that also exhibit the presence of a Dirac cone.

International audienc

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One of the major challenges for the reliable use of self-organization phenomena for device applications is to accurately position quantum dots on the surface. A promising way to get ordered dots is to use prepatterned substrates. We show that a combination of focused ion beam (FIB) prepatterned Si(001) substrates and self-assembled Ge quantum dots (QDs) leads to the precise placement of QDs. The technological advantages of this method are to control the Ge dots size and location, and to scale down the interdots distance to ∼20nm. Regarding more fundamental aspects, the accurate control of nanopatterns characteristics allows us to investigate the influence of various experimental parameters on QDs formation. The process proposed consists mainly of three steps: (1) FIB nanopatterning; (2) ex situ cleaning of the FIB-patterned substrate in order to fully remove the Ga contamination before introduction into the molecular beam epitaxy (MBE) chamber; and (3) Ge deposition by solid source MBE. After optimization of the growth parameters, nicely ordered dense arrays of homogeneous QDs are obtained. QDs are organized on the edges of the FIB holes at high temperature or inside the holes at lower temperature. We suggest that two different mechanisms of Ge dots formation are responsible of these results: kinetically limited nucleation at low temperature and stress driven nucleation at higher temperature.

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