Development of an HRTEM image analysis method to quantify carbon nanostructure

An analytical method for analyzing high-resolution transmission electron microscopy (HRTEM) images is presented. The method is composed of two major parts: digital image processing and lattice fringe characterization. The digital image processing is composed of the following operations: negative transformation, region of interest (ROI) selection, contrast enhancement, Gaussian lowpass filter, top-hat transformation (used to correct uneven illumination across an image), thresholding to obtain a binary image, morphological modification, clearing fringes on the ROI border, skeletonization, and removing short fringes that lack physical meaning. These operations are defined by equations with effects illustrated by images. The lattice fringe characterization generates statistics on fringe length, tortuosity, and separation based on the skeletons of the graphene layers. Fringe length and tortuosity are obtained automatically from the features of the skeletons, while fringe separation is obtained by analyzing manually selected fringe pairs. The algorithms are implemented within MATLAB, and demonstrated upon an exemplary HRTEM image of carbonaceous material. The image analysis algorithm permits quantitative HRTEM, here specifically addressing nanostructure of carbonaceous materials.