Electronic Excitation‐Driven β‐Ga ₂ O ₃ Metastability Transformation and Self‐Organization Mechanism: β→κ/γ/δ Phases

Irradiation-driven multiphase self-organization presents emergent opportunities for the customization of nanoscale engineering properties, dynamically tuning strain-field distributions and interfacial electronic structures. Responding to intense electronic excitation-induced energy deposition, the dominant phase transformations, with varying Gibbs free energy <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>Δ</mml:mi> <mml:mspace></mml:mspace> <mml:msubsup><mml:mi>G</mml:mi> <mml:mi>f</mml:mi> <mml:mi>o</mml:mi></mml:msubsup> </mml:mrow> <mml:annotation>$\Delta \ G_f^o$</mml:annotation></mml:semantics> </mml:math> , are confirmed as β → κ → γ → δ that are located in specific microregions for Gallium (III) oxide (Ga₂O₃), as follows: (i) Surface-localized interstitial accumulation under compressive stress triggers β → δ via semi-coherent interface formation. (ii) Tensile stress within latent tracks drives vacancy-mediated oxygen layer truncation (4/12 periodicity along ⟨0001⟩), stabilizing coherent 4H (ABCB) κ and 3C (ABC) β (ABC) interfaces through strain-compensated octahedral distortion. (iii) Screw dislocation-mediated lattice relaxation induces β → γ via cation disordering (Ga³⁺ occupancy at β-interstitial sites), forming metastable spinel γ with mixed occupancy across 16d/8a Wyckoff sites. Irradiation-driven β-Ga₂O₃→κ/γ/δ transitions, as mechanistically revealed via inelastic thermal spike (i-TS) calculations and molecular dynamics simulations, induce defect-mediated nonlinear photoresponse, critical for optoelectronic engineering.