STEM multiplication nano-moiré method with large field of view and high sensitivity.

Strain is one of the important factors that determine the photoelectric and mechanical properties of semiconductor materials and devices. In this paper, the scanning transmission electron microscopy multiplication nano-moiré method is proposed to increase the measurement range and sensitivity for strain field. The formation principle, condition, and measurement range of positive and negative multiplication moiré fringes (PMMFs and NMMFs) are analysed in detail here. PMMF generally refers to the multiplication of field of view, NMMF generally refers to the multiplication of displacement measurement sensitivity. Based on the principle of multiplication nano-moiré, Theoretical formulas of the fringe spacing and strain field are derived. Compared with geometric phase analysis of deformation measurements based on high-resolution atom images, both the range of field of view and the sensitivity of displacement measurements of the multiplication moiré method are significantly improved. Most importantly, the area of field of view of the PMMF method is increased by about two orders of magnitude, which is close to micrometre-scale with strain measurement sensitivity of 2 × 10-5. In addition, In order to improve the quality of moiré fringe and the accuracy of strain measurement, the secondary moiré method is developed.The strain laws at the interface of the InP/InGaAs superlattice materials are characterised using the developed method.