Environmental Electron Scanning Microscope

Abstract

This is the term paper for the course AEP 6610, reviewing the techniques and development of environmental scanning electron microscope (ESEM). The ESEM provides the ability to image samples down to nanometer scale without the necessity of high vacuum in the chamber and sample processing procedures. Therefore, samples can be imaged in its original hydrated state, preserving its dynamics, interior structures and morphology. Secondary electrons are collected to reveal the topology of the sample while backscattered electrons are collected to distinguish the element composition. In this paper, the resolution and limitations for ESEM are presented. The applications of ESEM on both organic and inorganic materials are discussed. Finally, future prospects an comparison with competing imaging technologies conclude the paper.

Introduction

The ESEM(Stokes 2008) was developed from conventional scanning electron microscopy (SEM)(Reimer 1978), preserving the principles of imaging and the resolution. The advancement and modification of SEM simplified the preparation of samples and allowed more complex imaging environment. The conventional SEM is a surface analytical technique; it has to be operated in high vacuum (\(\approx 10^{-5} \sim 10^{-7} \space Torr\)) chambers to prevent surface contamination. Therefore the samples must be clean, dehydrated, fixed and also conductive to avoid the charging effects. Toward these purposes, the samples are mostly pre-processed such as cooled, dehydrated and distorted, and usually coated with conducting materials, compromising the topographical and m