The last time we used a scanning electron microscope (a SEM), it looked like something from a bad 1950s science fiction movie. These days SEMs, like the one at the IBM research center, look like computers with a big tank poised nearby. Interestingly, the SEM is so sensitive that it has to be in a quiet room to prevent sound from interfering with images.

As a demo of the machine’s impressive capability, [John Ott] loads two US pennies, one facing up and one face down. [John] notes that Lincoln appears on both sides of the penny and then proves the assertion correct using moderate magnification under the electron beam.

Some electron microscopes pass electrons through thin samples much as light passes through a sample on a microscope slide. However, SEMs and REMs (reflection electron microscopes) use either secondary electron emission or reflected electrons from the surface of items like the penny.

You often see SEMs also fitted with EDS — energy dispersive X-ray spectrometers, sometimes called EDX — that can reveal the composition of a sample’s surface. There are other ways to examine surfaces, like auger spectrometers (pronounced like OJ), which can isolate thin films on surfaces. There’s also SIMS (secondary ion mass spectrometry) which mills bits of material away using an ion beam. and Rutherford backscattering spectrometry, which also uses an ion beam.

We keep waiting for someone to share plans to make a cheap, repeatable SEM. There are a few attempts out there, but we don’t see many in the wild. While the device is conceptually simple, you do need precise high voltages and high vacuums,. Also, you frequently need ancillary devices to do things like sputter gold in argon gas to coat nonconductive samples, so the barrier to entry is high.

According to [Asianometry], no one believed in the scanning electron microscope. No one, that is, except [Charles Oatley].The video below tells the whole story.

The Cambridge graduate built radios during World War II and then joined Cambridge as a lecturer once the conflict was over. [Hans Busch] demonstrated using magnets to move electron beams, which suggested the possibility of creating a lens, and it was an obvious thought to make a microscope that uses electrons.

After all, electrons can have smaller wavelength than light, so a microscope using electrons could — in theory — image at a higher resolution. [Max Knoll] and [Ernst Ruska], in fact, developed the transmission electron microscope or TEM.

The TEM works by passing an electron beam through a very thin sample and detecting it on the other side. However, the goal was to build an electron device that bounced electrons off an object — a SEM or scanning electron microscope. [Knoll] did build a device using this principle. However, it had a broad beam and could only magnify 10X or so, and it did not scan like a modern scope.

A practical SEM would wait for [Manfred Baron von Ardenne] in 1937. Working with Siemens (who, yes, owns Hackaday), he created a crude SEM. It took 20 minutes to create an image on a piece of film, so it wasn’t very practical. After two years, World War II broke out, and the work was lost.

At RCA, [Vladimir Zworykin] did some work on SEM, but abandoned the poorly-working device as TEM devices were more attractive. Then, in the 1950s, [Charles Oatley] decided he wanted to build an electron microscope for Cambridge.

Cambridge produced a very successful instrument that exploited secondary electrons and backscatter. They sold over 500 units. The video mentions that SEMs don’t require sample preparation, but they really don’t—they just don’t require thin slicing with a microtome. Semiconductor devices are often gold-coated to make the insulating surface conductive, for example, but that’s much easier to do than slicing very thin layers.

This is a great story of someone with a dream to create and took a shot. Granted, the time was right and the University was a bit easier to please than a conventional corporate overlord.

We are anxious for someone to create a DIY SEM that is buildable. For now, your best bet is to find a junker on the surplus market and fix it up.

Image credit: [Hannes Grobe] CC-BY-SA 2.5