Correlative STEM and SEM Imaging of PTB7:PC₇₁BM-Based Photoactive Layers in a Scanning Electron Microscope

Lowering the electron energy from values 80 keV in standard STEM experiments to 30 keV in scanning electron microscopes equipped with a STEM detector leads to the suppression of knock-on damage and contrast enhancement due to the increased scattering probability. The latter is favorable to distinguish weakly scattering materials with similar densities and average atomic numbers. Another advantage of scanning electron microscopes is the inherent availability of surface topography imaging by secondary electron (SE) SEM imaging, which can be used in a correlative manner in combination with STEM, i.e., SEM and STEM images are acquired in parallel revealing bulk structure and surface topography from exactly the same specimen region [1]. This is important because STEM contrast can be influenced by topography effects and SE SEM images support the interpretation of STEM images.