Cathodoluminescence in a Scanning Electron Microscope Operated in Transmission Mode

Abstract This study demonstrates the potential of correlative analysis cathodoluminescence (CL) carried out in a scanning electron microscope (SEM) operated in transmission mode in combination with a segmented detector. As demonstrated for the analysis of an (Al,Ga)N/AlN layer system, the use of 30 keV primary electrons permits the correlative recording of scanning transmission electron microscopy (STEM) bright field (BF), dark field (DF), high-angle annular dark field (HAADF), along with the CL signal. Despite the limitation to 30 keV, the transmitted electron signals provide an enhanced signal-to-noise ratio and improved chemical sensitivity as compared to any in-lens or chamber detector. Quantitative evaluation of the BF signal facilitates the estimation of sample thickness and identification of extended defects. The HAADF signal is significantly influenced by dynamical scattering effects, rendering material contrast highly thickness-dependent. Consequently, quantitative compositional analysis requires precise knowledge of the sample thickness, or alternatively, correlative analysis with spectrally resolved CL.