The Scanning Secondary Moiré Method with Atomic-Level Resolution and Large Micrometer-Scale Field of View

Abstract

The measurement field of view of the conventional transmission electron microscopy (TEM) nano-moiré and scanning transmission electron microscopy (STEM) nano-moiré methods is limited to the hundred-nanometer scale, unable to meet the deformation field measurement requirements of micrometer-scale materials such as transistors and micro-devices. This paper proposed a novel measurement method based on scanning secondary moiré, which can realize cross-scale deformation field measurement from nanometers to micrometers and solve the problem of insufficient measurement accuracy when using only the TEM moiré method. This method utilized the electron wave in the TEM passing through the atomic lattice of two layers of different materials to generate TEM moiré. On this basis, the TEM was tuned to the STEM mode, and by adjusting parameters such as the amount of defocusing, magnification, scanning angle, etc., the electron beam was focused on the position near the interface of the two layers of materials, and at the same time, the scanning line was made approximately parallel to the direction of one of the TEM moiré fringes. The scanning secondary moiré patterns were generated when the scanning spacing was close to the TEM moiré spacing. Through this method, the deformation field, mechanical properties, and internal defects of crystals can be detected by a large field of view with high sensitivity and high efficiency. Compared to traditional methods, the advantages of scanning secondary moiré method lie in significantly improving the measurement field of TEM moiré and STEM moiré methods, realizing the cross-scale visualization measurement from nanometers to micrometers, and possessing atomic-level displacement measurement sensitivity. It can also simplify and efficiently identify dislocations, offering a new method for large-area visualization observation of dislocation density in broad application prospects.