Reliability of the CFTM and GPA methods for strain analysis at ultra-thin layers

The reliability of the Computational Fourier Transform Moiré (CFTM) and Geometric Phase Analysis (GPA) techniques for strain analysis at ultra-thin layers has been investigated using computer-generated images. Our results revealed that the leakage effect creates error that is linearly dependent on the mask size used for Fourier filtering. Error due to the leakage effect has a significant impact on the analysis of strain for small-mismatched systems with low resolution in the original image. We demonstrate that the error due to the leakage effect can be minimized with improved resolution of the original image. In order to obtain a measurement of the reliability of the CFTM and GPA methods on ultra-thin layers, we systematically quantify the error due to the leakage effect as a function of image resolution and applied strain value for the original image. The presence of the leakage effect and the resulting limitations of the CFTM and GPA methods are demonstrated using a high-resolution transmission electron microscopy (HRTEM) image of an ultra-thin heterointerface from a strained layer superlattice.