arXiv subjects

Daniele Toffoli

Publications and source records attributed to Daniele Toffoli.

3 recordsLinked to original sources

arXiv2026

Surface Plasmons in the Continuum

The interest to foster plasmonic applications at energies in the ultra-violet, has escalated research initiatives in clusters of unconventional plasmonic materials like aluminum and indium,for which the surface-plasmon resonance appears above the ionization potential. Naturally, the quantum mechanical description calls for the incorporation of the ionization process, thereby making the ab initio calculations challenging. We present a robust approach within the time-evolution formalism of the time-dependent density-functional theory to calculate surface plasmon resonance in the continuum of metal clusters. Using the much studied Al$_{13}^-$ as a system of reference, we show that accurate description of the continuum and of the ionization of the cluster allow to capture a broad surface-plasmon in the UV. Application of this approach in aluminum clusters has given the size-dependent evolution from discrete spectral features in Al$_{6}$ to the surface-plasmon in larger clusters in the deep ultra-violet.

physics.chem-ph↗

arXiv2023

Development of a Selective Wet-Chemical Etchant for 3D Structuring of Silicon via Nonlinear Laser Lithography

Recently-demonstrated high-quality three-dimensional (3D) subsurface laser processing inside crystalline silicon (c-Si) wafers opens a door to a wide range of novel applications in multidisciplinary research areas. Using this technique, a novel maskless micro-pillars with precise control on the surface reflection and coverage are successfully fabricated by etching the laser processed region of c-Si wafer. To achieve this, a particular selective wet chemical etching is developed to follow subsurface laser processing of c-Si to reveal the desired 3D structures with smooth surfaces. Here, we report the development of a novel chromium-free chemical etching recipe based on copper nitrate, which yields substantially smooth surfaces at high etch rate and selectivity on the both laser-processed Si surface and subsurface, i.e., without significant etching of the unmodified Si. Our results show that the etch rate and surface morphology are interrelated and strongly influenced by the composition of the adopted etching solution. After an extensive compositional study performed at room temperature, we identify an etchant with a selectivity of over 1600 times for laser-modified Si with respect to unmodified Si. We also support our findings using density functional theory calculations of HF and Cu adsorption energies, indicating significant diversity on the c-Si and laser-modified surfaces.

physics.app-ph↗

arXiv2013

Si nano-VINe: Electrical Percolation in Quantum-Confined nc-Si:SiO2 Systems

Nanostructures, especially of silicon, are of paramount importance for new generation solar cell applications. The key material requirements for solar cells are good electrical conductivity, confinement of excitons, and a tunable band-gap that allows for tandem arrangements to absorb a maximally large portion of the solar spectrum. However, to date, existing Si-based nanostructures have addressed these requirements individually. The difficulty is that these requirements are entangled in complex ways, so an effort to improve one can lead to a major trade-offs in the others. In this study, we report on a novel silicon nanostructure, where the key advance is that we have managed to satisfy all the abovementioned requirements simultaneously: We demonstrate that the excitons are confined, the bandgap is tunable, and the electrons can freely travel along the nc-Si network.

cond-mat.mtrl-sci↗