Differential phase-contrast microscopy at atomic resolution

Abstract

A technique capable of detecting the electric field associated with individual atoms is now demonstrated. Atomic-resolution differential phase-contrast imaging using aberration-corrected scanning transmission electron microscopy provides a sensitive probe of the gradient of the electrostatic potential in a crystal lattice. Differential phase-contrast (DPC) imaging enhances the image contrast of weakly absorbing, low-atomic-number objects in optical and X-ray microscopy1,2,3,4. In transmission electron microscopy5, this same imaging mode can image magnetic fields in magnetic materials at medium resolution6,7. Atomic-resolution imaging of electromagnetic fields, however, is still a major challenge. Here, we demonstrate atomic-resolution DPC imaging of crystals using aberration-corrected scanning transmission electron microscopy. The image contrast reflects the gradient of the electrostatic potential of the atoms; that is, the atomic electric field, which is found to be sensitive to the crystal ionicity. Both the mesoscopic polarization fields within each domain and the atomic-scale electric fields induced by the individual electric dipoles within each unit cell can be sensitively detected in ferroelectric BaTiO3. The realization of atomic-resolution DPC microscopy opens a new dimension of microscopy from crystalline materials through to biological molecules.