arXiv subjects

Aldo Ugolotti

Publications and source records attributed to Aldo Ugolotti.

3 recordsLinked to original sources

arXiv2026

Interface stability of beta-Ga2O3 (100) on oxidized Si- and C-terminated 3C-SiC (001) substrates: a first-principles investigation

We provide a first-principles modeling of the beta-Ga2O3/3C-SiC interface that takes into account the reconstructions occurring at the 3C-SiC (001) surface by oxidation, aiming to mimic the actual deposition process under the best structural and thermodynamic conditions. Using density functional theory calculations, we systematically investigate the interface configurations between beta-Ga2O3 (100) and both Si- and C-terminated 3C-SiC (001) substrates, considering realistic oxidation states that form at the SiC surface prior to epitaxial growth. Our analysis evaluates different stacking sequences and atomic-scale bonding arrangements, computing adhesion energies for various interface geometries to determine their relative thermodynamic stability. This work addresses the critical need for understanding beta-Ga2O3 integration on substrates with superior thermal conductivity, providing a theoretical framework for optimizing heteroepitaxial growth conditions in ultra-wide-bandgap power electronics applications.

cond-mat.mtrl-sci↗

arXiv2024

Interface energies of Ga2O3 phases with the sapphire substrate and the phase-locked epitaxy of metastable structures explained

Despite the extensive work carried out on the epitaxial growth of Ga2O3, a fundamental understanding of the nucleation of its different metastable phases is still lacking. Here we address the role of interface energies by Density Functional Theory calculations of alpha, beta and kappa Ga2O3 on (0001) Al2O3 substrates, and different Ga2O3 interlayers. In conjunction to surface energies and misfit strain contribution, we demonstrate that alpha Ga2O3 is the preferred phase in 2D islands, when the low growth temperatures and the high growth rates hinder 3D island nucleation. This quantitatively explains the phase-locking in Mist-CVD experiments

cond-mat.mtrl-sci↗

arXiv2020

"Inside Out" Growth Method for High-Quality Nitrogen-Doped Graphene

High-quality nitrogen-doped graphene on nickel is prepared by exploiting both the catalytic properties of nickel and the solubility of nitrogen atoms into its bulk. Following the standard chemical vapor deposition procedure, a previously nitrogen-doped nickel substrate is exposed to carbon-containing precursors so that nitrogen atoms, segregating to the surface, remain trapped in the growing graphene network. Morphological and chemical characterization by scanning tunneling microscopy and X-ray photoelectron spectroscopy demonstrates that the process yields a flat, wide, continuous nitrogen-doped graphene layer. Experimental results are combined with a thorough density functional theory investigation of possible structural models, to obtain a clear description at the atomic scale of the various configurations of the nitrogen atoms observed in the graphene mesh. This growth method is potentially scalable and suitable for the production of high-performance nano-devices with well-defined nitrogen centers, to be exploited as metal-free carbon-based catalysts in several applicative fields such as electrochemistry, energy storage, gas storage/sensing or wastewater treatment.

cond-mat.mtrl-sci↗