Formation of Ag and Au Plasmonic Nanoparticles by Ion Implantation in Ga2O3 thin films

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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 × 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 incorporated fluences lower than nominal values, 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 that the need for thermal annealing to activate the localized surface plasmon resonance (LSPR) depends on the ion and implantation fluence considered. Additionally, we observed a redshift of the Ag LSPR peaks with increasing annealing temperature. X-Ray Diffraction (XRD) measurements showed a good crystallinity of the Ga 2 O 3 thin films, as well as improved crystallinity of the nanoparticles with annealing, becoming well-oriented with the matrix. Different possibilities for the origin of the observed LSPR shifts with annealing were identified and discussed, such as densification of the Ga 2 O 3 surrounding the nanoparticles, as well as changes to their shape and distribution, rather than changes in nanoparticle size. These results establish ion implantation as a viable approach for integrating plasmonic nanostructures into Ga 2 O 3 .