EM study of latent track morphology in TiO2 single crystals

A TEM investigation was conducted into the morphology of 167MeV Xe (2×1010cm−2 to 1014cm−2) and 1GeV Bi ion (2×1010cm−2) induced latent tracks in single crystal TiO2 (rutile). At fluences up to 1011cm−2 latent tracks are visible as discontinuous lines of strained crystal along the ion trajectory. From the implanted surface down to about 60–70nm below the surface the tracks appear as continuous conical structures with a base of diameter 5–6nm (Xe) and 8–9nm (Bi) in contact with the surface with a mushroom shaped hillock extending outward from the surface. At fluences between 6×1012cm−2 and 1013cm−2 the crystal is amorphized but rod-like crystalline regions remain which are oriented along the ion trajectories. Amorphization extends from the surface down to 8.3μm below suggesting an upper limit for the threshold electronic stopping power for amorphization of 7.3keVnm−1. At 1014cm−2 Xe the entire 8.3μm subsurface region is rendered amorphous although some evidence of short range ordering remains.