ABSTRACT
Atomic-resolution high-voltage electron microscopy (ARHVEM) was applied to analyze the chemical information around heterointerfaces of gallium nitride/AlN layers. The atomic positions of cations and nitrogen 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. Chemical composition of the sample did not change during the sample observation time. Degradation of the image quality may be due to the damaged surface layer produced during sample preparation. The sample preparation technique to obtain a damage-free sample of uniform thickness with heterophase interface is important for further investigation. The ARHVEM, thus, has been proved to be a powerful method for mapping elements with different contrasts at one-angstrom resolution, which will extend the application of transmission electron microscopy chemical characterization.
