Experimental investigation and simulation of SEM image intensity behaviors for developing thickness-controlled S/TEM lamella preparation via FIB-SEM.

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High-quality thin lamellae are essential for state-of-the-art scanning transmission electron microscopy (S/TEM) analyses. While the preparation of S/TEM lamellae using focused ion beam (FIB-) scanning electron microscopy (SEM) has been established since the early 21st century, two critical factors have only recently been addressed: precise control over lamella thickness and a systematic understanding of FIB-induced damage. This study conducts an experimental investigation and simulation to explore how the intensities of backscattered and secondary electrons (BSEs and SEs, respectively) depend on lamellae thickness for semiconductor (Si), insulator (Al2O3), and metallic (stainless-steel) materials. The BSE intensity shows a simple linear relationship with the lamella thickness for all materials below a certain thickness, whereas the relationship between the SE intensity and thickness is more complex. In conclusion, the BSE intensity is a reliable indicator for accurately determining lamella thickness across various materials during FIB thinning processing, while the SE intensity lacks consistency due to material and detector variability. This insight enables the integration of real-time thickness control into S/TEM lamella preparation, significantly enhancing lamella quality and reproducibility. These findings pave the way for more efficient, automated processes in high-quality S/TEM analysis, making the preparation method more reliable for a range of applications.