Radiation enhanced diffusion of Ti in Al2O3

Abstract

Titanium bulk and dislocation diffusion coefficients at 1000 °C have been determined for Ti in single crystal α-Al2O3(0001) for three types of samples: (i) Ti evaporated onto Al2O3, (ii) Ti+48at 100 eV deposited onto Al2O3, and (iii) Ti+48 at 100 eV deposited onto radiation damaged Al2O3 (damage inflected by implantation of Ti+46 at 7 keV). Diffusion penetration profiles were obtained by using secondary ion mass spectrometry depth profiling techniques. For the deposited and implanted Ti+ samples, the bulk diffusion coefficients (D) are 5.4×10−21 and 5.6×10−17 m2 s−1, respectively, and dislocation diffusion coefficients are 3.6×10−17 and 1.4×10−12 m2 s−1, respectively. Comparing the D's for Ti in the undamaged and damaged Al2O3, the D's for the latter samples are higher by a factor of 104–105, reflecting the radiation enhanced diffusion due to the defect structure inflected by the implanted 7 keV Ti+46. Comparing the D's for Ti deposited onto Al2O3 (both the evaporated and 100 eV Ti+48 samples) with those for Cr deposited onto Al2O3, the Ti D's are larger by a factor of 10, reflecting the influence of the valence state of the cation. These results show that cationic diffusion coefficients in Al2O3 can be controlled by varying the level of defects in the crystal.