Estimating the Spatial Distribution of Ca Dopants in α-SiAlON by Statistical Analysis of HAADF-STEM Image

Abstract

We analyzed the spatial distribution of Ca dopants in α-SiAlON by using a statistical approach that analyzed a high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) image. By evaluating the image intensity of each atomic column, we found that the intensity deviation of columns with Ca atoms was twice that of other atomic columns. The results of HAADF-STEM image simulation suggested that there was a long-range repulsive interaction along the [0001] direction between pairs of Ca atoms in the same Ca column. Moreover, correlation of image intensities in neighboring Ca columns suggested the existence of a short-range repulsive force between first-nearest-neighbor Ca atoms. The origin of such anisotropic interactions between pairs of Ca atoms will be discussed.