Robust Preparation of Sub‐20‐nm‐Thin Lamellae for Aberration‐Corrected Electron Microscopy

Abstract

AbstractAberration‐corrected scanning transmission electron microscopy (STEM) has been advancing resolution, sensitivity, and microanalysis due to the intense demands of atomic‐level microstructural investigations. Recent STEM technologies require preparing a thin lamella whose thickness is ideally below 20 nm. Although focused‐ion‐beam/scanning‐electron‐microscopy (FIB/SEM) is an established method to prepare a high‐quality lamella, nanometer‐level controllability of lamella thickness remains a fundamental problem. Here, the robust preparation of a sub‐20‐nm‐thin lamella is demonstrated by FIB/SEM with real‐time feedback from thickness quantification. The lamella thickness is quantified by back‐scattered‐electron SEM imaging in a thickness range between 0 and 100 nm without any reference to numerical simulation. Using real‐time feedback from the thickness quantification, the FIB/SEM terminates thinning a lamella at a targeted thickness. The real‐time feedback system eventually provides 1‐nm‐level controllability of the lamella thickness. As a proof‐of‐concept, a near‐10‐nm‐thin lamella is prepared from a SrTiO3 crystal by our methodology. Moreover, the lamella thickness is controllable at a target heterointerface. Thus, a sub‐20‐nm‐thin lamella is prepared from a LaAlO3/SrTiO3 heterointerface. The methodology offers a robust and operator‐independent platform to prepare a sub‐20‐nm‐thin lamella from various materials. This platform will broadly impact aberration‐corrected STEM studies in materials science and the semiconductor industry.