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Defect Spectroscopy and Defect Imaging
This behavior changes, if open volume defects (like vacancies, dislocations or grain boundaries) can be found in the bulk. Due to the missing positive charge, a potential that attract positrons forms at these sites. Positrons approaching them during the diffusion process can be trapped in their potential well and annihilate there.
The coincident detection of the energies of both annihilation quanta (CDBS) reveals detailed information about the contribution of core electrons. These element specific information allow the identification of the chemical vicinity at the annihilation site.
In our CDB spectrometer, the NEPOMUC positron beam is used and hence, the implantation region can be shifted from the surface region up to several micrometer into the specimen. By CDBS, a depth dependent chemical analysis of the defect sturucture can be performed. In conventional DBS, a depth dependent analysis allows the investigation of positron diffusion and further increases the sensitivity range in the case of saturated trapping.
Prof. Dr. Christoph Hugenschmidt
Phone: +49 (0)89 289-14609
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