Determining polarity and dislocation core structures at atomic level for epitaxial AlN/(0001)6H-SiC from a single image in HRTEM

Abstract

The polarity of epitaxial AlN film grown on (0001)6H-SiC and dislocation core structures in the film have been studied using a 200 kV LaB6 high-resolution transmission electron microscope of point resolution about 0.2 nm. A posterior image processing technique, the image deconvolution, was utilized to transform a single [21¯1¯0] image that does not intuitively represent the structure into the projected structure map. The adjacent Al and N projected atomic columns with the interatomic distance 0.109 nm can be distinguished from each other by analyzing the image contrast change with the sample thickness based on the pseudo-weak phase object approximation. This makes possible to derive the polarity and core structures of partial dislocations in the epitaxial AlN film at atomic level from a single image without relying on any other additional structure information. The atomic configurations for two partial dislocations containing a 10-atom ring and a 12-atom ring, respectively, have been attained. The method is available for II-VI and other III-V compounds. Its principle and procedure are briefly introduced.