Doping of sapphire single crystals with $^{111}$In and $^{111m}$Cd detected by perturbed angular correlation

The electric hyperfine interaction of ion beam implanted /sup 111/In and /sup 111m/Cd probe atoms in sapphire (Al/sub 2/O/sub 3/) single crystals has been investigated using perturbed angular correlation spectroscopy. For both probe atoms the same distinctive electric field gradient was found, indicating that nearly all the implanted probe atoms form a stable substitutional configuration in the temperature range between 77 K and 873 K on the aluminum sublattice. A comparative study between /sup 111/In and /sup 111m/Cd-measurements points to a dynamic interaction initiated by the electron-capture of /sup 111/In(EC)/sup 111/Cd similar to In/sub 2/O/sub 3/ and La/sub 2 /O/sub 3/. Size and orientation of the EFG are discussed in comparison to experimental results in Cr/sub 2/O/sub 3/ single crystals. (10 refs).