HRTEM image simulation of rhenium (VI) oxide using multislice technique

• Main Author: Poh, Kah Kiong.
• Other Authors: Oh Joo Tien
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Materials::Testing of materials
• Online Access: http://hdl.handle.net/10356/48442
• Institution: Nanyang Technological University

As defects and impurities are present in all materials, High Resolution Transmission Electron Microscopy (HRTEM) images of materials recorded experimentally from Transmission Electron Microscope (TEM) usually contains artefacts. Artefacts make the interpretation of the experimentally recorded HRTEM images difficult and simulated HRTEM images are needed for comparison. Thus, the objective of this project is to simulate the HRTEM images of Rhenium (VI) Oxide using the Multislice method and determine how the sample thickness, defocus values and accelerating voltage used affect the resolution of the simulated HRTEM image. The atom coordinates of the Rhenium (VI) Oxide were measured using a crystal visualization program, Crystal Maker for Windows, and the data collected are inputted into the simulation programs. The simulation programs used in this project are ATOMPOT, MULSLICE and IMAGE programs and their functions are calculate atomic potential, Multislice layer and generate simulated image respectively. By using the calculated Scherzer defocus and Contrast Transfer Function (CTF), it is found out that the optimum resolution for the simulated HRTEM image of Rhenium (VI) Oxide has the defocus value of 700Å, sample thickness of 100Å and accelerating voltage of 200keV is used. When the image plane is moved further from the Scherzer defocus, over-focus and under-focus occur and the simulated images have poor resolution and sharpness. Furthermore, when the thickness of the sample increases, the resolution of the simulated image decreases because there is an increase interference and diffraction on electron wave’s path. Moreover, the resolution of the simulated HRTEM image increases as the accelerating voltage used increase up to a certain limit. This is because electron beam of shorter wavelength is produced when higher accelerating voltage is used. After the limit, further increase of the accelerating voltage will cause the resolution of the simulated HRTEM image to decrease because the band good transmittance in CTF decreases.