Implantation sites of Ce and Gd in diamond

The implantation sites of rare earth (RE) probes Ce-141 (t(1/2) = 32 d) and Gd-149 (t(1/2) = 9.28 d) in diamond have been investigated using the emission channeling (EC) technique. Parent isotopes Cs-141 and Dy-149 were implanted into type IIa diamond samples at an energy of 60 keV at the online isotope separator ISOLDE at CERN. Cs-141 decays through the chain Cs-141-Ba-141-La-141-Ce-141-Pr-141. EC measurements were made on the 102 keV conversion electrons emitted in the decay of Pr-141 to its ground state. The decay of Dy-149 follows the chain Dy-149-Tb-149-Gd-149-Eu-149-(149) Sm. EC measurements were made on the 101 keV electrons emitted in the decay of Eu-149. Two-dimensional channeling patterns of the conversion electrons were obtained along <110> and <111> 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. (C) 2002 Elsevier Science B.V. All rights reserved.