Introduction to Scanning Electron Microscopy

Introduction To Scanning Electron Microscopy

At the completion of the prac, the practical experience of operating a scanning electron microscope is sufficient to operate the particular machine in the future. During the experiment, two different gold plated samples are analysed under the SEM and compositional and topographic information is identified and analysed. Both the information is derived by changing the working distance, accelerating voltage, aperture size, probe current, resolution and magnification.

AIM

To analyse samples and obtain micrographs of the surface, using a scanning electron microscope. The experimental images are compared against the different material structures and defects between the various samples at different magnifications and resolutions.

INTRODUCTION

A schematic of a scanning electron microscope is shown below. The instrument can be separated into three major sections including electron-optical ‘column’, vacuum system and electronics and display system.

Figure 1: Layout off scanning Electron Microscope.

In the optical part of instrument, the first thing we notice is the need for a source of illumination. No visible photons of light are produced within the SEM but an invisible beam of electrons. The beam is produced from an electron ‘gun’ and a cross-section through a simplified electron gun is shown below.