Understanding the effect of gas pressure on electron diffraction patterns acquired using a scanning electron microscope

Abstract

This project is dealing with electron backscattered diffraction (EBSD) where the pressure is varied inside the scanning electron microscope (SEM) chamber by introducing some gas in the sample chamber. The application of EBSD in material science has empowered the relationship of the microstructural composition of crystalline grains with various other properties of the materials. Utilization of low vacuum measurement environments prevents charge build-up for insulating specimens that leads to unclear patterns. Here, the purpose is to analyse and compare EBSD results obtained by using different pressure conditions inside the SEM chamber. ESPRIT Dynamics was employed to provide a simulation of the electron backscatter patterns (EBSP). The image processing package Fiji was applied for image processing of EBSPs. To explain the information provided by the Kikuchi bands observed in the EBSPs, which set of planes produce a given Kikuchi band is described. EBSPs acquired at different pressures from a silicon sample were analysed by calculating the cross-correlation coefficient (CC) on comparing the experimental EBSPs with simulated patterns. The main intention of this project was to explore the effect on the EBSPs of changing the pressure inside the chamber. It is observed that by letting some gases inside the chamber to bring down the difficulties related to charging, reduces the quality of the patterns, leading to a decrease in the quantity of information found from these patterns.