DIOGO Disorder Induced Ordering in Gallium Oxide

• Titov, Andrei; Klevtsov, Anton; Fedorenko, Elizaveta; Azarov, Alexander; Kuznetsov, Andrej & Karaseov, Platon (2025). Density and fractality of collision cascades in α-Ga2O3. Applied Physics Letters. ISSN 0003-6951. 127(15). doi: 10.1063/5.0288966. Fulltekst i vitenarkiv Vis sammendrag

  Control over radiation defect generation is essential while applying ion-beam technology to materials. In this work, we study disorder formation in rhombohedral polymorph of gallium oxide (α-Ga2O3) as a function of the bombarding ion mass. As such, we discriminate the impact of the collision cascades density, specifically its impact on the surface amorphization rates in α-Ga2O3. Importantly, along with collecting experimental data, we calculated collision cascades parameters using different algorithms based on the binary collision approximation predicting disorder accumulation trends observed in the experiments. Furthermore, we showed that collision cascades in α-Ga2O3 can be modeled within a fractal geometry framework, correlating fractal dimension with the collision cascade density. These results enhance the understanding of radiation defects in Ga2O3 polymorphs, applicable in the development of the ion beam technology in these interesting materials.

• Azarov, Alexander; Fernandez, Javier Garcia; Zhao, Junlei; He, Ru; Park, Ji-Hyeon & Jeon, Dae-Woo [Vis alle 9 forfattere av denne artikkelen] (2025). Phase glides and self-organization of atomically abrupt interfaces out of stochastic disorder in α-Ga2O3. Nature Communications. 16. doi: 10.1038/s41467-025-58516-9. Fulltekst i vitenarkiv Vis sammendrag

  Disorder-induced ordering and remarkably high radiation tolerance in γ-phase of gallium oxide is a recent spectacular discovery at the intersection of the fundamental physics and electronic applications. Importantly, by far, these data were collected with initial samples in form of the thermodynamically stable β-phase of this material. Here, we investigate these phenomena starting from metastable α-phase and explain radically new trend occurring in the system. We argue that in contrast to that in β-to-γ disorder-induced transitions, the O sublattice in α-phase exhibits hexagonal close-packed structure, so that to activate α-to-γ transformation significant structural rearrangements are required in both Ga and O sublattices. Moreover, consistent with theoretical predictions, α-to-γ phase transformation requires accumulation of the substantial tensile strain to initiate otherwise impossible lattice glides. Thus, we explain the experimentally observed trends in term of the combination of disorder and strain governed process. Finally, we demonstrate atomically abrupt α/γ interfaces paradoxically self-organized out of the stochastic disorder.

• Azarov, Alexander; Radu, Cristian; Galeckas, Augustinas; Mercioniu, Ionel Florinel; Cernescu, Adrian & Venkatachalapathy, Vishnukanthan [Vis alle 11 forfattere av denne artikkelen] (2025). Self-Assembling of Multilayered Polymorphs with Ion Beams. Nano Letters. ISSN 1530-6984. 25(4), s. 1637–1643. doi: 10.1021/acs.nanolett.4c05727. Fulltekst i vitenarkiv
• Klevtsov, Anton; Karaseov, Platon; Azarov, Alexander; Karabeshkin, Konstantin; Fedorenko, Elizaveta & Titov, Andrei [Vis alle 7 forfattere av denne artikkelen] (2024). Non-linear effects in α-Ga2O3 radiation phenomena. APL Materials. 12(11). doi: 10.1063/5.0235497. Fulltekst i vitenarkiv Vis sammendrag

  The rhombohedral phase of gallium oxide (α-Ga2O3) is of interest because of its highest bandgap among the rest of the Ga2O3 polymorphs, making it particularly attractive in applications. However, even though the ion beam processing is routinely used in device technology, the understanding of radiation phenomena in α-Ga2O3 is not mature. Here, we study non-linear effects for radiation disorder formation in α-Ga2O3 by varying both the defect generation rate and the density of collision cascades, enabled by comparing monoatomic and cluster ion implants, also applying systematic variations of ion fluxes. In particular, we show that the collision cascade density governs the surface amorphization rates, also affected by the ion flux variations. These trends are explained in terms of the non-linear in-cascade and inter-cascade defect interactions occurring during ballistic and dynamic defect annealing stages. As such, these data reveal new physics of the radiation phenomena in α-Ga2O3 and may be applicable for more predictive ion beam processing of α-Ga2O3-based devices.

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