Gianfranco Sfuncia

Thermal management is a major challenge in densely integrated photonic systems, yet the mechanisms governing heat generation in operating nanoscale devices remain poorly understood. Here, the spatio-temporal evolution of thermal loads in an electrically driven GeSn/SiGeSn multiple-quantum-well microdisk laser is resolved using a multimodal approach combining time-resolved operando Dark-Field X-ray microscopy, electro-thermal finite-element simulations, and three-dimensional focused ion beam–scanning electron microscopy tomography. With nanosecond temporal and sub-200 nm spatial resolution, this methodology directly visualises heat-induced lattice strain and enables quantitative reconstruction of the corresponding temperature field under realistic electrical injection conditions. Heat generation is strongly localised within the electrical contact area in Ge layer rather than in the gain medium. Current crowding at the contacts creates nanoscale hot areas that induce asymmetric strain fields extending into the active region, resulting in spatially non-uniform optical gain. Contact architecture, current injection uniformity, and interfacial defects emerge as the primary factors governing thermal loading and device-to-device performance variability. These results establish contact-mediated Joule heating as the dominant thermal bottleneck in electrically pumped group-IV microlasers and identify contact engineering as a direct route to improved performance. More broadly, they show that thermal behaviour in nanoscale photonic devices is governed primarily by current injection pathways and structural design, thereby providing a framework for developing thermally robust, CMOS-compatible light sources.

Synthesis of hexagonal boron nitride (hBN) on CMOS-compatible substrates is desirable for large-scale fabrication of hBN-based micro- and optoelectronic devices. However, growth of well-oriented, high-quality hBN films via chemical vapor deposition (CVD) on silicon substrates is still challenging. We report a new method to synthesize ultrathin, well-oriented hBN films on Si(001) substrates, based on a continuous flow CVD process using borazine as a single-source precursor. In addition, spectroscopic ellipsometry is explored as a fast, nondestructive method to determine the thickness, refractive index, and optical bandgap of the grown hBN films. The resulting hBN films exhibit a thickness of 7 ± 1 layers, near perfect stoichiometry, a surface roughness of 1.1 nm, a refractive index of 2.17 at 633 nm, and an optical bandgap of 5.89 eV. The use of borazine precursor avoids the availability of reactive nitrogen species and thus prevents the formation of an amorphous SiN_x interlayer at the Si interface.

Photoactive devices embedding MoS2 thin layers between indium tin oxide (ITO) and fluorine doped tin oxide have been prepared by electrodeposition of MoS2. In order to improve carrier transport capability, the interface between MoS2 and ITO has been engineered with the introduction of a thin MoO3 layer. The effect of MoS2 concentration in the electrodeposition solution has been investigated. The structure and the optical properties of electrodeposited MoS2 have been studied by Raman spectroscopy, UV–Vis measurements, and transmission electron microscopy. The photoelectric response has been investigated using a 630 nm laser as a function of the power and applied voltage. The device with MoO3 shows promising external quantum efficiencies, from ≈0.25% at zero bias up to ≈50% at a bias of 1.6 V.

A hydrogel formulation of 2-hydroxy ethyl methacrylate (HEMA) containing covalently linked magnetite nanoparticles was developed to actively facilitate the selective removal and photocatalytic degradation of antibiotics. To this purpose, the hybrid materials were molecularly imprinted with Lomefloxacin (Lome) or Ciprofloxacin (Cipro), achieving a selectivity of 60% and 45%, respectively, starting from a solution of XX concentration. After the adsorption, the embedded magnetite was used with the double function of (i) magnetically removing the material from water and (ii) triggering photo-Fenton (PF) reactions assisted by UVA light and H₂O₂ to oxidize the captured antibiotic. The success of the material design was confirmed by a comprehensive characterization of the system from chemical–physical and morphological perspectives. Adsorption and degradation tests demonstrated the material’s ability to efficiently degrade Lome until its complete disappearance from the electrospray ionization (ESI) mass spectra. Regeneration tests showed the possibility of reusing the material for up to three cycles. Ecotoxicological tests using algae Rapidocelis subcapitata, crustaceans Daphnia magna, and bacteria Vibrio fischeri were performed to evaluate the ecosafety of our synthesized materials.

New fluorescent carbon nanoparticles, obtained using artichoke extract, have been used for the ultrasensitive (sub-nanomolar) and selective detection of dopamine in artificial saliva samples.