Marco Malvestuto

Probing Long‐Lived Plasmonic‐Generated Charges in TiO2/Au by High‐Resolution X‐ray Absorption Spectroscopy

Exploiting plasmonic Au nanoparticles to sensitize TiO2 to visible light is a widely employed route to produce efficient photocatalysts. However, a description of the atomic and electronic structure of the semiconductor sites in which charges are injected is still not available. Such a description is of great importance in understanding the underlying physical mechanisms and to improve the design of catalysts with enhanced photoactivity. We investigated changes in the local electronic structure of Ti in pure and N-doped nanostructured TiO2 loaded with Au nanoparticles during continuous selective excitation of the Au localized surface plasmon resonance with X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). Spectral variations strongly support the presence of long-lived charges localized on Ti states at the semiconductor surface, giving rise to new laser-induced low-coordinated Ti sites.

Revisiting the Local Structure in Ge-Sb-Te based Chalcogenide Superlattices.

The technological success of phase-change materials in the field of data storage and functional systems stems from their distinctive electronic and structural peculiarities on the nanoscale. Recently, superlattice structures have been demonstrated to dramatically improve the optical and electrical performances of these chalcogenide based phase-change materials. In this perspective, unravelling the atomistic structure that originates the improvements in switching time and switching energy is paramount in order to design nanoscale structures with even enhanced functional properties. This study reveals a high- resolution atomistic insight of the [GeTe/Sb2Te3] interfacial structure by means of Extended X-Ray Absorption Fine Structure spectroscopy and Transmission Electron Microscopy. Based on our results we propose a consistent novel structure for this kind of chalcogenide superlattices.

Influence of TiO2 electronic structure and strong metal–support interaction on plasmonic Au photocatalytic oxidations

Aiming at understanding how plasmonic reactions depend on important parameters such as metal loading and strong metal–support interaction (SMSI), we report the plasmonic photodegradation of formic acid (FA) under green LED irradiation employing three TiO2 supports (stoichiometric TiO2, N-doped TiO2, black TiO2) modified with Au nanoparticles (NPs) 3–6 nm in size. The rate of FA photooxidation follows different trends depending on Au loading for stoichiometric and doped Au/TiO2 materials. In the first case, the only contribution of hot electron transfer produces a volcano-shaped curve of photoreaction rates with increasing Au loading. When TiO2 contains intra-bandgap states the photoactivity increases linearly with the amount of Au NPs due to the concomitant enhancement produced by hot electron transfer and plasmon resonant energy transfer (PRET). The role of PRET is supported by finite element method simulations, which show that the increase in both Au NP inter-distance and SMSI enhances the probability of charge carrier generation at the Au/TiO2 interface.

Interband characterization and electronic transport control of nanoscaled GeTe / Sb 2 Te 3 superlattices

The extraordinary electronic and optical properties of the crystal-to-amorphous transition in phase-change materials have led to important developments in memory applications. A promising outlook is offered by nanoscaling such phase-change structures. Following this research line, we study the interband optical transmission spectra of nanoscaled

Extreme ultraviolet resonant inelastic X-ray scattering (RIXS) at a seeded free-electron laser

\text{GeTe}/{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}

Ultrafast Ge-Te bond dynamics in a phase-change superlattice

chalcogenide superlattice films. We determine, for films with varying stacking sequence and growth methods, the density and scattering time of the free carriers, and the characteristics of the valence-to-conduction transition. It is found that the free carrier density decreases with increasing GeTe content, for sublayer thicknesses below

MagneDyn: the beamline for magneto dynamics studies at FERMI

\ensuremath{\sim}3

MagneDyn: the future beamline for ultrafast magnetodynamical studies at FERMI

nm. A simple band model analysis suggests that GeTe and

Direct probe of the variability of Coulomb correlation in iron pnictide superconductors

{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}

Ultralow-fluence single-shot optical crystalline-to-amorphous phase transition in Ge–Sb–Te nanoparticles

layers mix, forming a standard GeSbTe alloy buffer layer. We show that it is possible to control the electronic transport properties of the films by properly choosing the deposition layer thickness, and we derive a model for arbitrary film stacks.