Crystallization Instead of Amorphization in Collision Cascades in Gallium Oxide.

Disordering of solids often leads to amorphization, but polymorph transitions, facilitated by favorable atomic rearrangements, may temporarily help to maintain long-range periodicity in the solid state. In far-from-equilibrium situations, such as atomic collision cascades, these rearrangements may not necessarily follow a thermodynamically gainful path, but may be kinetically limited. In this Letter, we focus on such crystallization instead of amorphization in collision cascades in gallium oxide (Ga_{2}O_{3}). We determine the disorder threshold for irreversible β→γ polymorph transition and explained why it results in elevating energy to that of the γ polymorph, which exhibits the highest polymorph energy in the system below the amorphous state. Specifically, we demonstrate that upon reaching the disorder transition threshold, the Ga sublattice kinetically favors transitioning to the γ-like configuration, requiring significantly less migration for Ga atoms to reach the lattice sites during postcascade processes. As such, our data provide a consistent explanation of this remarkable phenomenon and can serve as a toolbox for predictive multipolymorph fabrication.