Spatially resolved X-ray fluorescence maps were presented that showed the

introduction and the evolution of oxygen vacancies in chromium-doped strontium

titanate during an electric-field-driven insulator-to-metal transition. The vacancies

were introduced at the anode and diffuse through the crystal toward the cathode.

The spatial distribution of vacancies was explained by a model describing the

electrical breakdown as a percolation process. Strong differences in the vacancy

distribution were found when the transition took place in air and in a hydrogenenriched

atmosphere. In air, the vacancies disappeared from the surface, whereas in

the reducing hydrogen atmosphere, they remained at the surface.

Spatial Distribution of Oxygen Vacancies in Cr-Doped SrTiO3 During an Electric-

Field-Driven Insulator-to-Metal Transition. B.P.Andreasson, M.Janousch,

U.Staub, G.I.Meijer: Applied Physics Letters, 2009, 94[1], 013513