We present a novel, simple and low-cost protocol for fabricating pure Si, or Si1−xGex or Ge-based, sub-micrometric dielectric antennas with ensuing hybrid integration into different plastic supports. The dielectric antennas are realized exploiting the natural instability of thin solid films to form regular patterns of monocrystalline atomically smooth SiGe nanostructures that cannot be realized with conventional methods. By adjusting the annealing treatment and the semiconductor film thicknesses, different classes of nanoarchitectures can be formed, from elongated and periodic structures to disordered structures with a footprint of just a few tens of nm. This latter disordered case presents a significant suppression of the large-scale fluctuations that are conventionally observed in ordered systems and shows an almost hyperuniform behavior character.
Solid state dewetting (SSD) is a natural shape instability occurring in thin solid films when heated at high temperature: it transforms a flat layer in isolated islands. SSD can be efficiently exploited in several fields, including flexible photonics, photocatalysis or dielectric Mie resonator, to form perfectly ordered and complex nano-architectures over large scales, as well as randomly organized, isolated islands.
Among the dewetting systems reported in literature, in our group SiGe dewetting, i.e. SiGe structures directly formed on an electrically insulating and optically transparent substrate, has been efficiently exploited to realize arrays of nanostructures with footprint ranging from few nm up to several μm. Additionally, dewetting of Ge, which is of particular interest for photonic devices working at near and mid-infrared frequency, has recently started to be investigated. This work purpose is to study dewetted SiGe and Ge islands and to exploit them to produce flexible films for photonic sensing applications. In particular, also an innovative approach to transfer SiGe and Ge dewetted islands into a flexible substrate such as polydimethylsiloxane (PDMS) will be presented.
We present a novel approach to create spinodal-like structures appropriately modulating the instability of the solid state dewetting: many materials, indeed, featuring anomalous suppression of density fluctuations over large length scales are emerging systems known as disordered hyperuniform. The underlying hidden order renders them appealing for several applications, as light management and topologically protected electronic states. These applications require scalable fabrication, which is hard to achieve with available top-down approaches. These spinodal materials are used by a hybrid top-down/bottom-up approach based on sol-gel dip-coating and nano-imprint lithography for the faithful reproduction of the disordered metasurfaces in metal oxides (SiO2 and TiO2).
In this work, we present preliminary results of the fabrication and characterization of 1D Fabry–Perot microcavity realized on Yb3+ activated SiO2-SnO2 glass-ceramic (SiO2-SnO2:Yb3+). A radiofrequency-sputtering/sol-gel hybrid deposition process was developed for the microcavity fabrication. The fabrication included (i) radiofrequency-sputtering (rf-sputtering) of SiO2/HfO2 Bragg reflectors and (ii) sol-gel deposition of the active SiO2-SnO2:Yb3+ defect layer. A good control and enhancement of the spontaneous emission for Yb3+ luminescence sensitized by SnO2 nanocrystals was achieved exploiting microcavity properties. Such results are valuable for development of low-threshold rare-earth-based coherent light sources, pumped by broadband UV diodes.
As already done in electronics, passive and active photonic devices demand integration on flexible substrates for a broad spectrum of application ranging from optical interconnection to sensors for civil infrastructure and environments, to coherent and uncoherent light sources and functionalized coatings for integration on biological tissue. In this communication we will present some recent results concerning the fabrication of novel flexible optical layers by sol-gel and radio frequency sputtering deposition techniques. The perspective is to give a technological way to transform intrinsically rigid or brittle materials into a highly mechanically flexible and optically functional systems
KEYWORDS: Germanium, Electron beam lithography, Atomic force microscopy, Reactive ion etching, Silicon, Plasma enhanced chemical vapor deposition, Photomasks, Quantum dots, Scanning electron microscopy, Chemical elements
We make use of electron beam lithography (EBL) and reactive ion etching (RIE) techniques to realize periodic masks
with elements of nanometric size. Epitaxial growth of Si layers and SiGe alloys on or through such a mask leads to the
formation of structures such as quantum dots and quantum rings. We will show that by making use of EBL and RIE it
has been possible to obtain preferential sites for the nucleation of Ge islands on Si(001). EBL has been optimized in
order to obtain circular pits with diameters ranging from 80 to 200 nm and depth from 30 to 80 nm. AFM images of the
patterned substrates confirm the regularity and reproducibility of patterning in terms of form and dimension. The
subsequent deposition of a thin film of Ge results in the nucleation of Ge islands at preferential sites. The precise
positioning of Ge islands may be an optimal solution for obtaining self-assembled and well-ordered Ge nanostructures,
leading to a number of new applications, for example within the field of quantum computing.
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