Ion beam radiation damage effects in rutile (TiO 2)

Abstract

Radiation damage accumulation in the rutile phase of titanium dioxide (TiO 2) have been studied by Rutherford Backscattering Spectroscopy in channeling geometry (RBS/c) and by transmission electron microscopy (TEM). A large temperature dependence of damage accumulation in rutile was observed. Defect accumulation determined in situ by RBS/c occurs far more rapidly in samples irradiated at 160 K compared to 300 K. A rutile single crystal irradiated at 160 K was rendered fully amorphous at a fluence of 4 × 10 18 Xe 2+/m 2, compared to a critical amorphization fluence of 8 × 10 19 Xe 2+/m 2 for a crystal irradiated at 300 K. In samples irradiated at 300 K a defect denuded zone at the crystal surface was observed to accompany a buried damage layer. In samples irradiated at 160 K, no defect denuded zone was observed. These observations indicate that there is a large temperature dependence associated with thermally activated point defect mobility in rutile. Moreover, in in situ irradiation experiments using 1.5 MeV Xe + ions, a critical amorphization temperature of 200 K was observed. The rutile structure is much more susceptible to radiation damage induced by point defect accumulation, compared to dense collision cascades. In the experiments presented here, only the He + ion irradiation leads to complete amorphization, combined with substantial changes in the micro-hardness and elastic (Young's) modulus.