Role of the interface on radiation damage in the SrTiO₃/ LaAlO₃ heterostructure under Ne²⁺ ion irradiation

We systematically investigated the microstructural evolution of heteroepitaxial SrTiO₃ (STO) thin films grown on a single crystal LaAlO₃ (LAO) (001) substrate, focusing on the response of the STO/LAO interface to Ne²⁺ irradiation at room temperature. Cross sectional transmission electron microscope (TEM) analysis reveals that the LAO crystal amorphizes first after a relatively low dose of damage followed by the amorphization of the STO film after irradiation to a higher dose. While the critical dose to amorphize differs between each material, amorphization begins at the interface and proceeds outward in both cases. Thus, a crystalline/amorphous interface first forms at the STO/LAO interface by a dose of 1 dpa, and then an amorphous/amorphous interface forms when the dose reaches 3 dpa. Scanning TEM and x-ray energy dispersive spectroscopy indicate no significant heavy cation elemental diffusion, though electron energy loss spectroscopy reveals a redistribution of oxygen across the film/substrate interface after Ne²⁺ irradiation. Atomistic calculations are used to interpret the experimental findings in terms of the defect properties in each of the two component phases.