Implantation sites of Ce and Gd in diamond

The implantation sites of rare earth (RE) probes 141Ce (t1/2=32 d) and 149Gd (t1/2=9.28 d) in diamond have been investigated using the emission channeling (EC) technique. Parent isotopes 141Cs and 149Dy were implanted into type IIa diamond samples at an energy of 60 keV at the online isotope separator ISOLDE at CERN. 141Cs decays through the chain 141Cs-141Ba-141La-141Ce-141Pr. EC measurements were made on the 102 keV conversion electrons emitted in the decay of 141Pr to its ground state. The decay of 149Dy follows the chain 149Dy-149Tb-149Gd-149Eu-149Sm. EC measurements were made on the 101 keV electrons emitted in the decay of 149Eu. Two-dimensional channeling patterns of the conversion electrons were obtained along <1 1 0> and <1 1 1> axial directions by raster scans with a Si surface barrier detector. Comparison of the observed patterns with simulated spectra show that in diamond 45-50% of the RE atoms are located near substitutional sites, unlike the case in Si