Radiation enhanced diffusion of Ti in Al2O3

Titanium bulk and dislocation diffusion coefficients at 1000 degrees C have been determined for Ti in single crystal alpha-Al2O3(0001) for three types of samples: (i) Ti evaporated onto Al2O3, (ii) (48)Ti(+)at 100 eV deposite d 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 p enetration profiles were obtained by using secondary ion mass spectrometry depth profiling techniques. For the deposited and implanted Ti+ samples, th e bulk diffusion coefficients (D) are 5.4x10(-21) and 5.6x10(-17) m(2) s(-1 ), respectively, and dislocation diffusion coefficients are 3.6x10(-17) and 1.4x10(-12) m(2) s(-1), respectively. Comparing the D's for Ti in the unda maged and damaged Al2O3, the D's for the latter samples are higher by a fac tor of 10(4)-10(5), 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(+) sam ples) with those for Cr deposited onto Al2O3, the Ti D's are larger by a fa ctor of 10, reflecting the influence of the valence state of the cation. Th ese results show that cationic diffusion coefficients in Al2O3 can be contr olled by varying the level of defects in the crystal. (C) 2000 American Ins titute of Physics. [S0021-9606(00)70627-1].