Solid-state dewetting of Si(Ge)-based complex nano-architectures and their applications in photonics

Dewetting is a ubiquitous phenomenon in nature: many different thin films of organic and inorganic substances share this shape instability driven by surface tension and mass transport. This spontaneous phenomenon leads a thin film to break and drip in isolated islands. I will address two distinct cases of solid-state dewetting: 1) templated dewetting of silicon and 2) spontaneous dewetting of silicon-germanium. Templated solid-state dewetting can be used to frame complex nanoarchitectures, nanowires (up to 0.75 mm long) and connected circuits of monocrystalline silicon on insulator with unprecedented precision and reproducibility over large scales [1]. Phase-field simulations quantitatively benchmark the experimental results revealing the dominant role of surface diffusion as a driving force for dewetting and the role of faceting in stabilizing the nanostructures. I will discuss the use of these ordered structures as dielectric antennas (Mie resonators) for visible and NIR light manipulation [2]. Spontaneous dewetting of thick SiGe layers leads to the onset of spinodal-like structures as accounted for by the features of Minkowski-functionals and evolution of Betti numbers [3]. The formation of these disordered structures is interpreted in the framework of the Cahn-Hilliard-Cook theory of phase separation in analogy with spinodal dewetting of polymers and liquid-metals. I will discuss the possibility to exploit this bottom-up, self-assembly method to form hyper-uniform, dielectric metasurfaces at visible and near-infrared frequencies [4] over ultra-large scales.

References

[1] M. Naffouti et al., Sci. Adv. 2017; Bollani et al., Nat. Comm. 2019
[2] M. Abbarchi et al. ACS nano 2014; T. Wood et al. ACS photonics 2017.
[3] M. Salvalaglio et al., Phys. Rev. Lett. 2020
[4] Z. Ma et al., Journal of Applied Physics 121, 244904 (2017)

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