Experimental and atomistic modelling study of ion irradiation damage in thin crystals of the TiO_2 polymorphs

摘要

Thin crystals of rutile, brookite, and anatase were irradiated in-situ with 1.0 MeV Kr using the TVEM-TANDEM facility. Synthetic rutile and cassisterite (SnO_2, rutile structure) remained crystalline up to 5 x 10~(15) ion cm~(-2) at 50 K. Natural brookite and anatase with low impurity levels became amorphous at 8.1 ± 1.8 x 10~(14) and 2.3 ± 0.2 x 10~(14 )ions cm~(-2), respectively, at 50 K. Irradiation at higher temperature revealed T_c = 170 K for brookite and 242 K for anatase. Natural rutile with about 2 wt% impurities became amorphous at 9.4 ± 1.8 x 10(14) ions cm~(-2) at 50 R and has a T_c = 207 K. The available data reveal both a structural effect in the polymorphs with low levels of chemical impurities and a chemical effect in natural rutile specimens containing up to about 1.7 wt% impurities.^