One-angstrom-resolution element mapping by phase contrast ARHVEM technique

Atomic-resolution high-voltage electron microscopy (ARHVEM) was applied to analyze the chemical information around heterointerfaces of GaN/AlN layers. The atomic positions of cations and N could be directly determined from a single image using ARHVEM. With assistance of computer simulations, it become apparent that the contrast of the cations varied depending on their elements in ARHVEM images, under appropriate defocus conditions and within a certain region of crystal thickness. The experimentally observed ARHVEM images were compared with simulated images, and the GaN/AIN structure was analyzed at the atomic level.