Papers by Author: G. Pasold

Abstract: Silicon carbide (SiC) was investigated for deep band gap states of europium by means of deep level transient spectroscopy (DLTS). The knowledge of the properties of optoelectrically active impurities or defects is essential for a detailed understanding of the energy-transfer process resulting in the observable excitations [1]. SiC-samples of the polytypes 4H as well as 6H are ion-implanted by different europium- isotopes in order to obtain a chemical identification of the characterized energy levels. Here the concentration sensitivity of the DLTS is applied to observe the elemental transmutation of the incorporated radioactive tracer atoms 146Eu (t1/2=4.51 d) and 147Eu (t1/2=24.6 d). DLTS on samples implanted with stable Eu-ions (153Eu) was carried out for comparison and manifestation of the results. From these studies 5 Eu-related deep band gap levels are established: in 4H-SiC two levels at EV+0.86(2) eV and EC−0.47(2) eV, and in 6H-SiC three levels at EV+0.88(2) eV, EC−0.29(2) eV and EC−0.67(2) eV.

Abstract: Diffusion of 6Li in the refractory metals Ta and W has been studied using the nondestructive neutron depth profiling technique. The preliminary results point out the complex behavior of 6Li atoms in W and Ta. The experiment showed that the Fickian diffusion is affected by the presence of traps and radiation defects in the sample surface layer. Further experiments and computer simulations of the diffusion process are in progress.