Abstract
Very recently, we learned that the phase stability of Ga2O3 polymorphs is readily controllable by the accumulation of radiation damage. Thus, using ion beams, different Ga2O3 phases may be stabilized at different spatial locations of ion beam penetration, which can be exploited for thermal energy management. Particularly, in this work we present heat conduction properties of the double polymorph γ/β-Ga2O3 structures, fabricated by a self-organized γ-polymorph transformation induced in β-Ga2O3 by irradiation. The thermal conductivity was measured by time-domain thermoreflectance method. The results show an order of magnitude difference in thermal conductivity across the γ/β interface. Moreover, we demonstrate that γ-Ga2O3 films exhibit remarkably high radiation tolerance in terms of thermal transport for consequent radiations with swift heavy ions. We also present the thermal transport properties of other Ga2O3 polymorphs and discuss phase-dependent thermal conductivity through phonon transport properties like phonon mean free path and phonon density of states. The molecular dynamics simulations with machine-learned potential are also presented to validate the experimental results.