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Background

I set up my Scanning Electron Microscope (SEM) facility in early 2016 with three objectives in mind. These are:


What is an SEM?

An SEM is an instrument that is capable of providing highly magnified images of a specimen placed in the chamber of the microscope. Subjects may be biological, which is the type of subject I usually image, or more relevant to materials science or physics.

The SEM uses a beam of electrons to create the image of the specimen, rather than light as is used in conventional microscopy. The electron beam is scanned across the surface of the object and electrons released at the surface of the specimen by the interaction of the beam and the specimen are detected and used to create an image of the specimen’s surface. While an SEM is capable of producing much higher magnifications than light microscopy, or to be more precise, much higher resolutions, it is often used at magnifications of between x50 and x1,000 because it gives a much greater depth of field than is possible with a light microscope, as is illustrated below. Among the disadvantages of an SEM over a light microscope are the fact that an SEM is many times more expensive than a conventional light microscope and also, the image does not contain any colour information. Furthermore, it is necessary to dry the specimen without deforming it and then to coat it with a very thin layer of gold or similar conducting material before placing it in the chamber of the SEM.














About this Site

The site consists of the following pages, which can be accessed using the navigation bar at the top of each page or the links below:


Introduction

Illustrating the difference of depth of field between an image from a conventional light microscope (left) and a scanning electron microscope (right). In the left hand image only a small fraction of the micro-fossil is in focus, whilst in the SEM image the whole specimen is in focus. Note also that the light micrograph is in colour while the SEM one is monochrome.

Spiders - click here to be taken to the spider sub-domain