Daniele Pergolesi

Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially 18O substituted La0.6Sr0.4MnO3 target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

Enhanced Proton Conductivity in Y‐Doped BaZrO3 via Strain Engineering

Abstract The effects of stress‐induced lattice distortions (strain) on the conductivity of Y‐doped BaZrO3, a high‐temperature proton conductor with key technological applications for sustainable electrochemical energy conversion, are studied. Highly ordered epitaxial thin films are grown in different strain states while monitoring the stress generation and evolution in situ. Enhanced proton conductivity due to lower activation energies is discovered under controlled conditions of tensile strain. In particular, a twofold increased conductivity is measured at 200 °C along a 0.7% tensile strained lattice. This is at variance with conclusions coming from force‐field simulations or the static calculations of diffusion barriers. Here, extensive first‐principles molecular dynamic simulations of proton diffusivity in the proton‐trapping regime are therefore performed and found to agree with the experiments. The simulations highlight that compressive strain confines protons in planes parallel to the substrate, while tensile strain boosts diffusivity in the perpendicular direction, with the net result that the overall conductivity is enhanced. It is indeed the presence of the dopant and the proton‐trapping effect that makes tensile strain favorable for proton conduction.

Pulsed Laser Deposition of Superlattices Based on Ceria and Zirconia

Rapidly growing attention is being recently directed towards the ninvestigation of the ionic conducting properties of oxide film nhetero-structures. Experimental evidence has been reported nshowing that interfacial phenomena at hetero-phase interfaces ngive rise to faster ion conduction pathways than the bulk or nhomo-phase interfaces. Nonetheless, a deeper understanding of nthe interface transport properties is still needed to exploit these neffects. In this work, we have investigated the growth mechanism nof different superlattices fabricated by pulsed laser deposition n(PLD) coupling doped and undoped cerium and zirconium noxides. Single crystalline MgO wafers were selected as ndeposition substrates. The superlattice structures were obtained nby means of a thin buffer layer of SrTiO3 (STO). The growth nmechanism was investigated by reflection high energy electron ndiffraction (RHEED) and X-ray diffraction (XRD) analyses.