Speaker
Description
Gallium oxide (Ga₂O₃) is a compelling member of the polymorphic oxide family, where ion beam modification offers a powerful route to tailor material structure and functionality. While the creation of defects in this crystal through elastic energy transfer (Sₙ) is well established and drives, for example, monoclinic‑to‑orthorhombic transformations, the role of inelastic energy loss (Sₑ) remains more complex, particularly when the material already contains disorder. In this context, it is important that the fundamental understanding of how Ga₂O₃ responds to highly-ionizing swift heavy ion (SHI) irradiation does not lag behind insights gained for other semiconductors and complex oxides [KTaO₃ - G. Velișa et al., J. Phys. D: Appl. Phys. 2021].
To address this gap, we designed an experiment to test whether damage‑reducing and damage‑enhancing mechanisms can coexist under identical SHI irradiation conditions. β‑Ga₂O₃ samples were first pre‑damaged using 1.2 MeV Au ions from the 3MV Tandetron™ from IFIN-HH at fluences of 0.3, 1.0 and 10.0 nm⁻², generating controlled initial disorder states, and then irradiated at room temperature with 8.6 MeV/u Au ions (Sₑ ≈ 43 keV/nm) at GSI. Ex-situ RBS/C measurements, performed at IFIN-HH, quantified damage evolution before and after irradiation in both undamaged and pre-damaged samples.
The SHI response was found to depend strongly on the initial defect state. The least‑damaged sample exhibited partial recovery of pre‑existing defects, consistent with electronic‑excitation‑induced annealing [Iancu et al., Scripta Mater. 2025], while the most heavily pre‑damaged sample showed clear signatures of ion‑track formation, with data also hinting at localized phase transformation around the track core, in agreement with recent computer simulations [Han et al., Adv. Sci. 2025]. These results demonstrate that the initial disorder state acts as a tunable variable for selectively activating ionization‑driven processes in Ga₂O₃.