Direct Imaging of Spatially Varying Potential and Charge across Internal Interfaces in Solids

Transmission electron holography is utilized to study the electrostatic potential and associated space charge across grain boundaries in SrTi${\mathrm{O}}_3$. While pristine boundaries show only the effect of a reduction in density of atoms, doped boundaries indicate the presence of potential barriers and associated space charge due to accumulation of charged point defects. This Letter demonstrates the viability of electron holography as a bulk sensitive tool to directly image and quantify the magnitude, sign, and spatial extent of electrical potential and charge across internal interfaces in solids.