This guide teaches you how to use a TEM from scratch. It assumes no prior knowledge. In particular, it does not assume that you know anything about physics, optics or scattering theory.

There are many excellent textbooks available to teach you all about electron microscopy in detail (eg, Williams and Carter; Goodhew, Humphreys and Beanland). The approach here is much less formal, and it will teach all sorts of things that lots of people don't think that you need to know. This is because, in my experience, knowing a bit about the inside of a machine can very quickly demystify the strange art of electron microscopy.

I have visited many laboratories in my life, and it never ceases to amaze how many people do things with TEMs which simply don't make any sense to them at all (or anyone else for that matter). When trying to line up a machine, they will say things like: 'Well, you turn this knob until the thing that goes in-and-out like that goes in-and-out like this, then switch this button and do it again.' If you ask them why they do these things they say; 'Erm... well, because that's what you do.'

All this is well and good until something goes wrong or the person who knows how to do all this leaves the laboratory. Local knowledge can slowly decay into complete misinformation. Sometimes, results still come out, but not at the highest performance of the microscope. In many laboratories, whole operating modes (eg STEM mode on a TEM/STEM) remain idle because nobody knows what that strange switch does...

Learning to use a TEM in this sort of environment is really difficult. On a big modern machine, say a FEG TEM/STEM with energy-filtered imaging there are dozens of bits and pieces, computers and underlying variables. It can all seem utterly overwhelming. How do you begin to learn to use this monster?

In my opinion the way to proceed is hands-on, right from the word go. Learn about one control, and understand it thoroughly. In this guide, I have several pages on just the first knob we discuss - the intensity knob. When I teach TEM, I always have a pen and paper to hand. I frantically draw ray-diagrams explaining what each control does. Many people would say, 'but John, nobody needs to know what double-deflection coils are.' At one level that is completely true. If you are a molecular biologist who needs some TEM micrographs, then perhaps you should just do what somebody tells you to do. However, I guarantee in the long run you learn much, much quicker if you have a model in your mind of what is going on inside a TEM. After all, these machines are really very logical. The complication lies in the layers inter-relatedly variables. Understand what is going on, and it will all become much easier.

Now read on...

Copyright J M Rodenburg