Positrons enable analysis of defects in functional materials

Positron annihilation spectroscopy (PAS) is an advanced experimental technique that allows to study of extended and point defects and their agglomeration down to the atomic scale. The main strength of PAS is its excellent resolution to detect low concentrations (0.1 to 100 ppm) of vacancy-like defects. Using our slow positron beams at the positron ELBE (pELBE) facility, not only volumetric capability is achieved, but also defect profilometry over the depth of the sample in the sub-micron range. The other advantage of PAS is the interaction of positrons with core electrons, which carry information about the local atomic environment. The combination of all these characteristics allows the successful analysis of defect nanostructures in many classes of materials. Some research highlights will be presented, including investigations of the role of defects in heavily doped semiconductors, magneto-ionic oxides and nitrides, and superconductors. An overview of current collaborations within the HZDR and with external users will be given, as well as an outlook on future positron activities, including the increasing focus on kinematic pump-and-probe experiments associated with intense lasers and electric fields, and perspectives related to the upcoming DALI project.