Donor Defect Mobilization in Transparent Oxides Via High Energy Proton Irradiation—Implications for Space Applications

Tin-doped indium oxide (ITO) is a versatile transparent conductive material widely used in electronics, photonics, and optoelectronics, necessitating a comprehensive understanding of its behavior under extreme environments. Here we study proton radiation effects in ITO and reveal the subtle interplay between displacement defect formation and electronic ionization upon irradiation. Guided by Monte Carlo simulations, we irradiate 100 nm thick ITO films with 20 keV and 1 MeV protons that fully penetrate the films mimicking polyenergetic and omnidirectional radiation in space orbits. We find that while both proton energies activate donor defects via atomic displacements, electronic ionization associated with 1 MeV protons further mobilizes these defects resulting in a ~7% improvement in electronic conductivity at 10¹⁴ cm^-2 fluence. X-ray diffraction experiments suggest a ~15% increase in nanocrystalline size, while reflectance enhancement observed at 600 – 800 nm points toward an increased free-carrier concentration. The interaction is simulated via a cascade irradiation molecular dynamics model explaining the role inelastic thermal spikes play in activating displacement defects. Our findings have implications for space applications of transparent oxides and suggest that electronic ionization can improve these materials.