The resolution capability of the scanning electron microscope has increased immensely in recent years, and is now within the sub-nanometre range, at least for inorganic materials. An equivalent advance has not yet been achieved for imaging the morphologies of nanostructured organic materials, such as organic photovoltaic blends. Here we show that energy-selective secondary electron detection can be used to obtain high-contrast, material-specific images of an organic photovoltaic blend. We also find that we can differentiate mixed phases from pure material phases in our data. The lateral resolution demonstrated is twice that previously reported from secondary electron imaging. Our results suggest that our energy-filtered scanning electron microscopy approach will be able to make major inroads into the understanding of complex, nano-structured organic materials.

We have quantified two-dimensional dopant profiles in Si with high accuracy using a commercial field emission gun scanning electron microscope with added secondary electron energy-filtering capabilities. Quantification was achieved for dopant concentrations of $2.8\times {10}^{17}–7.5\times {10}^{19}{\mathrm{cm}}^{-3}$ with an accuracy of $\pm 8.5\%$ . Using energy filtering, we have measured the surface potential difference $\Delta {\Phi }_s$ across a $3\mathrm{nm}$ wide $p$ -doped Si layer with respect to the $n$ -doped substrate of a test structure to be $0.72\pm 0.15\mathrm{V}$ . Spatial resolution limits are discussed and are shown to be limited by the secondary electron escape depth. A technique for the rapid collection of calibrated energy-filtered images is also proposed.