RESUMO
A systematic study is presented in which multilayers of different composition (W/Si, Mo/Si, Pd/B(4)C), periodicity (from 2.5 to 5.5 nm) and number of layers have been characterized. In particular, the intrinsic quality (roughness and reflectivity) as well as the performance (homogeneity and coherence of the outgoing beam) as a monochromator for synchrotron radiation hard X-ray micro-imaging are investigated. The results indicate that the material composition is the dominating factor for the performance. By helping scientists and engineers specify the design parameters of multilayer monochromators, these results can contribute to a better exploitation of the advantages of multilayer monochromators over crystal-based devices; i.e. larger spectral bandwidth and high photon flux density, which are particularly useful for synchrotron-based micro-radiography and -tomography.
RESUMO
The successful application of the rapid thermal annealing (RTA) process for creation of a magic denude zone in individual Czochralski silicon wafers is based on vacancy controlled oxygen precipitation. The kinetics of the vacancy and self-interstitial processes in Si wafers are studied in this paper. Detailed insight into nucleation processes, out-diffusion and vacancy-interstitial recombination during the RTA leads to a new model of interaction between vacancies and oxygen. The calculation of the distribution function of these defects follows from modified Becker-Döring equations transformed for vacancies and interstitials and extended by diffusion and recombination terms. The new model, which includes the vacancy influence on oxygen nucleation and which follows from this theoretical analysis, corresponds very well to the experimental properties of formation of bulk micro-defects during RTA processes.
