Lattice disorder and radiation enhanced annealing in La-implanted TiO_2 single crystals

摘要

Rutherford backscattering spectrometry and channeling were used to characterize the disorder produced by implantation of La ions into TiO_2 (rutile) single crystals at substrate temperatures T_i between 77 and 1100 K. Complete amorphization was observed at T_i of 77 and 300 K for La fluences of 1 x 10~(15) cm~(-2) and 2 x 10~(15) cm~(-2), respectively. At T_i equal to 300 K and fluences of 1 x 10~(15) cm~(-2), radiation-enhanced annealing starts to affect the disorder profile. The recovery occurs preferentially in the near-surface region. With increasing T_i, two recovery stages of the lattice disorder, between 300 and 500 K and above 700 K, have been observed. These stages are about 200 K lower than those observed for subsequent isochronal annealing of an amorphous TiO_2 layer. At T_i equal to 1100 K recovery of the lattice disorder was nearly complete. A minimum yield of 2.5% was reached, similar to that of the virgin crystal. Radiation-enhanced diffusion of La into TiO_2 leads to an estimated substitutional component of 35%.