A study on the effect of TEM operating variables on the theoretical images of crystalline solids, silicon nitride

Abstract

This study aims to investigate the effects of defocus, sample thickness, accelerating voltage and aperture size on high resolution transmission electron microscopy (HRTEM) images of β-Si3N4 . This is done by employing the multislice method, which requires β-Si3N4 supercell to be constructed. Then, each atom coordinates of the supercell is measured using ImageJ program. Specific information regarding the material are subsequently input into simulation programs; ATOMPOT, MULTISLICE and IMAGE. It is assumed that β-Si3N4 is a perfect crystal and simulated image is perfectly coherent. The simulated images were then compared with published results.

It is concluded that HRTEM images of β-Si3N4 has optimum resolution at defocus value of 700Å, sample thickness between 2.909Å to 58.18Å, accelerating voltage of 200keV and aperture size of 10mrad. These results are consistent with published works, theoretical calculations, contrast transfer function (CTF) and intensity profiles. Additionally, the phenomenon of blurring on all simulated HRTEM images and its effect on resolution is examined. Various limitations of the study are briefly discussed as well.