ION-BEAM RADIATION-DAMAGE EFFECTS IN RUTILE (TIO2)

Radiation damage accumulation in the rutile phase of titanium dioxide (TiO2) have been studied by Rutherford Backscattering Spectroscopy in channeling geometry (RBS/c) and by transmission electron microscopy (T EM). A large temperature dependence of damage accumulation in rutile w as observed. Defect accumulation determined in situ by RBS/c occurs fa r more rapidly in samples irradiated at 160 K compared to 300 K, A rut ile single crystal irradiated at 160 K was rendered fully amorphous at a fluence of 4 x 10(18) Xe2+/m(2), compared to a critical amorphizati on fluence of 8 x 10(19) Xe2+/m(2) for a crystal irradiated at 300 K. In samples irradiated at 300 K a defect denuded zone at the crystal su rface was observed to accompany a buried damage layer. In samples irra diated at 160 K, no defect denuded zone was observed. These observatio ns indicate that there is a large temperature dependence associated wi th thermally activated point defect mobility in rutile. Moreover, in i n situ irradiation experiments using 1.5 MeV Xe+ ions, a critical amor phization temperature of 200 K was observed. The rutile structure is m uch more susceptible to radiation damage induced by point defect accum ulation, compared to dense collision cascades. In the experiments pres ented here, only the He+ ion irradiation leads to complete amorphizati on, combined with substantial changes in the micro-hardness and elasti c (Young's) modulus. (C) 1998 Elsevier Science B.V. All rights reserve d.