Materials science and engineering b-solid state materials for advanced technology vol:105 issue:1-3 pages:106-110
The lattice site location of excited states of Eu-149 was studied by means of the emission channeling technique. The 60 keV implantation of Tb-149 into a GaN thin film was performed at room temperature up to a dose of 2.0 x 10(13) cm(-2). This radioactive isotope eventually decays into short-lived excited states of 149Eu. The conversion electrons emitted in the subsequent decay to the Eu-149 ground state were detected with a position sensitive detector. We measured their angular distributions around the , ,  and  axes in the as-implanted state and after 600 and 900 C vacuum annealing. Already in the as-implanted state around 65% of (149)*Eu atoms were found on substitutional Ga sites. The root mean square (rms) displacements from the substitutional sites in the as-implanted state were found to be around 0.13-0.16 Angstrom. Annealing up to 600degreesC increased the substitutional fraction by a few percent and slightly reduced the rats displacements, most likely due to the removal of crystal defects in the vicinity of the Eu atoms, resulting in a better incorporation into substitutional sites. (C) 2003 Elsevier B.V. All rights reserved.