arXiv subjects

Ângelo Rafael Granadeiro da Costa

Publications and source records attributed to Ângelo Rafael Granadeiro da Costa.

4 recordsLinked to original sources

arXiv2026

Formation of Ag and Au Plasmonic Nanoparticles by Ion Implantation in Ga$_2$O$_3$ thin films

Gallium oxide (Ga$_2$O$_3$) is a wide-bandgap semiconductor with exceptional electrical and optical properties, making it a promising material for optoelectronic and sensing applications. In this work, we demonstrate for the first time the formation of plasmonic silver (Ag) and gold (Au) nanoparticles embedded in Ga$_2$O$_3$ thin films via ion implantation. Ga$_2$O$_3$ films deposited by RF sputtering on sapphire substrates were implanted with Ag or Au ions at 150 keV and a nominal fluence of 5 $\times$ 10$^{16}$ ions/cm$^2$, followed by thermal annealing between 200 and 700 °C. Rutherford backscattering spectrometry (RBS) measurements revealed saturation effects during implantation, resulting in lower incorporated fluences, as well as out-diffusion with post-implantation annealing. Transmission electron microscopy confirmed the formation of metallic nanoparticles with a distribution consistent with the metal profiles measured by RBS. Optical absorption measurements showed a pronounced localized surface plasmon resonance (LSPR) band in the Ag-implanted films, visible even in the as-implanted state and red-shifting with increasing annealing temperature, while Au-implanted films exhibited a distinct LSPR peak only after annealing at $\geq$500 °C. The observed LSPR shifts with annealing are attributed primarily to changes in the Ga$_2$O$_3$ matrix rather than a change in nanoparticle size. These results establish ion implantation as a viable approach for integrating plasmonic nanostructures into Ga$_2$O$_3$.

cond-mat.mtrl-sci↗

arXiv2026

Au and Ag nanoparticles produced by ion implantation in single-crystalline $β$-Ga$_2$O$_3$

This work reports the successful formation of Ag and Au nanoparticles in $β$-Ga$_2$O$_3$ single-crystals by ion implantation and annealing at 550 °C. X-ray diffraction measurements revealed that nanoparticles were formed after the annealing step, presenting a highly-ordered crystalline structure and conforming to a crystallographic relation with respect to the matrix: $\left(0\overline{1}0\right)_β\parallel \left(110\right)_{\mathrm{Ag/Au}}$ and $\left[102\right]_β\parallel \left[1\overline{1}2\right]_{\mathrm{Ag/Au}}$. The presence of these nanoparticles was also confirmed via absorbance measurements revealing the localised surface plasmon resonance peaks associated with these particles. Considering the multiple advantages and the versatility of metallic nanoparticles, their combination with the exceptional properties of $β$-Ga$_2$O$_3$ paves the way for a wide range of applications.

cond-mat.mtrl-sci↗

arXiv2026

Anisotropic implantation damage build-up and crystal recovery in $β$-Ga$_2$O$_3$

The present work aims at investigating the defect accumulation and recovery dynamics in the inherently anisotropic $β$-Ga$_2$O$_3$ lattice. A systematic Rutherford Backscattering Spectrometry in Channelling mode (RBS/C) analysis of Cr-implanted samples was performed across multiple surface orientations and channelling directions. Distinct apparent defect accumulation and annealing rates were observed along different channelling axes, mainly attributed to the shadowing of certain types of defects along some directions. The efficient defect removal observed after annealing was correlated with the strain relaxation observed via High-Resolution X-ray diffraction (HRXRD) at temperatures as low as 500 °C, which is attributed to the removal of point defects. Annealing at higher temperature further improves crystalline quality but at a slower rate. In short, this work enhances the understanding of the effect of structural anisotropic properties of $β$-Ga$_2$O$_3$ during ion implantation, as well as the crystal recovery during thermal annealing, highlighting the interplay between crystallography and defect dynamics.

cond-mat.mtrl-sci↗

arXiv2026

Understanding the anisotropic response of $β$-Ga$_2$O$_3$ to ion implantation

While $β$-Ga$_2$O$_3$ is considered a promising wide bandgap semiconductor, the impact of ion-induced defect formation and anisotropic elasticity remains poorly understood. Here, we combine a simulation and experiment X-ray diffraction (XRD) study of the strain-stress dynamics induced by ion implantation into $β$-Ga$_2$O$_3$ single-crystals with different surface orientations. The strain accumulation in the out-of-plane direction is observed by XRD to occur in an anisotropic manner, with compressive strain along the [010] direction and tensile strain along the directions perpendicular to (100) and (001). An anisotropic stress/strain accumulation model is proposed and probed via Molecular Dynamics (MD), showing an excellent agreement with the experiments. For higher damage levels, pole figures obtained both experimentally and by MD via a novel reciprocal-space projection method reveal an orientation-independent $β$-to-$γ$ phase transition, with a fixed crystallographic relationship between the polymorphs. By exploring the strain-stress dynamics in anisotropic systems, this work establishes a method to directly compare macroscale diffraction experiments and atomistic simulations and opens a new path to engineer the properties of such systems utilizing their anisotropic response to ion implantation/irradiation.

cond-mat.mtrl-sci↗