Tiny Art Etched into Silicon Wafers with Electron Beam Lithography

Looks like [Sam Zeloof] got bored on his Thanksgiving break, and things got a little weird in his garage. Of course when your garage contains a scanning electron microscope, the definition of weird can include experimenting with electron-beam lithography, resulting in tiny images etched into silicon.

You’ll probably remember [Sam] from his 2018 Hackaday Superconference talk on his DIY semiconductor fab lab, which he used to create a real integrated circuit. That chip, a PMOS dual-channel differential amp, was produced by photolithography using a modified DLP projector. Photolithography imposes limits to how small a feature can be created on silicon, based on the wavelength of light.

[Sam] is now looking into using the electron beam of his SEM as a sort of CNC laser engraver to produce much finer features. The process involves spin-coating silicon wafers with SU-8, an epoxy photoresist normally used with UV light but that also turns out to be sensitive to electron beams. He had to modify his SEM to control the X- and Y-axis deflection with a 12-bit DAC and provide a custom beam blanker. With a coated wafer in the vacuum chamber, standard laser engraving software generates the G-code to trace his test images on the resist. A very quick dip in acetone develops the exposed chip.

[Sam] says these first test images are not too dainty; the bears are about 2.5 mm high, and the line width is about 10 μm. His system is currently capable of resolving down to 100 nm, while commercial electron beam lithography can get down to 5 nm or so. He says that adding a Faraday cage to the setup might help him get there. Sounds like a project for Christmas break.

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My Oscilloscope Uses Fire

If you want to visualize sound waves, you reach for your oscilloscope, right? That wasn’t an option in 1905 so physicist [Heinrich Rubens] came up with another way involving flames. [Luke Guigliano] and [Will Peterson] built one of these tubes — known as a Rubens’ tube — and will show you how you can, too. You can see a video of their results, below. Just in case a flame oscilloscope isn’t enough to attract your interest, they are driving the thing with a theremin for extra nerd points.

The guys show a short flame run and one with tall flames. The results are surprising, especially with the short flames. Of course, the time base is the length of the tube, so that limits your measurements. The tube has many gas jets along the length and with a sound source, the height of the flames correspond to the air pressure from the sound inside the tube.

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Crystal Oscillators Explained

We’ve read a lot about oscillators, but crystal oscillators seem to be a bit of a mystery. Hobby-level books tend to say, build a circuit like this and then mess with it until it oscillates. Engineering texts tend to go on about loop gains but aren’t very clear about practice. A [circuit digest] post that continues a series on oscillators has a good, practical treatment of the subject.

Crystals are made to have a natural resonant frequency and will oscillate at that frequency or a multiple thereof with the proper excitation. The trick, of course, is finding the proper excitation.

The post starts with a basic model of a crystal having a series capacitance and inductance along with a resistance. There’s also a shunt or parallel capacitor. When you order a crystal, you specify if you want the resonant frequency in series or parallel mode — that is, which of the capacitors in the model you want to resonate with the inductor — so the model has actual practical application.

By applying the usual formula for resonance on the model you’ll see there is a null and a peak which corresponds to the two resonance points. The dip is the series frequency and the peak is the parallel. You can actually see a trace for a real crystal in a recent post we did on the Analog Discovery 2. It matches the math pretty well, as you can see on the right.

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Air Bubble Characters Float Along This Unique Scrolling Display

We’ve seen a lot of unique large-format scrolling message boards on these pages, but most of them use some sort of established technology – LEDs, electromechanical flip-dots, and the like – in new and unusual ways. We’re pretty sure this air-bubble dot matrix display is a first, though.

While it may not be destined for the front of a bus or a train station arrivals and departures board, [jellmeister]’s bubble display shows some pretty creative thinking. It started with a scrap of multiwall polycarbonate roofing – Corotherm is the brand name – of the type to glaze greenhouses and other structures. The parallel tubes are perfect for the display, although individual tubes could certainly be substituted. A plastic end cap was fabricated; air nozzles in each channel were plumbed to an air supply through solenoid valves. An Arduino with a couple of motor driver hats allows pulses of air into each channel to create reasonably legible characters that float up the tube. The video below shows it in use at a Maker Faire, where visitors could bubble up their own messages.

It took some tweaking to get it looking as good as it does, but there’s plenty of room for improvement. We wonder whether colored liquid might help, or perhaps adding a Neopixel or even a laser to each channel to add some contrast. Maybe something to cloud the water slightly would help; increasing the surface tension with a salt solution might make the bubbles more distinct. We doubt it’ll ever have the contrast ratio of a flip-dot display, but it certainly has a charm all its own.

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Treasure Trove of Projects Provides Endless Examples

Sometimes, traveling the internet feels a little like exploring an endless cave system looking for treasure. Lots of dark passageways without light or life, some occasional glimmers as you find a stray gold doubloon or emerald scattered in a corner. If we take the metaphor too far, then finding [Paul]’s “Little Arduino Projects” repository is like turning an unremarkable corner only to discover a dragon’s hoard.

LEAP (as [Paul] also refers to the collection) is a numbered collection of what looks like more or less every electronics project he has completed over the last few years. At the time of writing there are 434 projects in the GitHub repository and tagged and indexed in a handy blog-style interface. Some are familiar, like a modification to a Boldport project. Others are one-off tests of a specific concept like driving a seven segment display (there are actually 16 similar projects if you search the index for “7-Segment”). On the other end are project builds with more detailed logs and documentation, like the LED signboard for monitoring the status of 24 in-progress projects, mounted in a guitar fret board.

LEAP reminds us of the good old days on the internet, before it felt like 50% trolling and 50% tracking cookies. Spend a few minutes checking out [Paul]’s project archive and see if you find anything interesting! We’ve just scratched the surface. And of course, send a tip if you discover something that needs a write-up!

Look Like A Movie Hacker

On the old original Star Trek series, they bought some futuristic salt and pepper shakers to use on an episode. The problem is they didn’t look like salt and pepper shakers, so they used normal ones instead and turned the strange-looking ones into Dr. McCoy’s medical instruments. This demonstrates the value of looking like what you claim to be. So sure, you are a super skillful hacker, but if you are sitting in front of a normal looking computer desktop, how can anyone tell? After all, in the movies, hackers use exotic flashy user interfaces, right? Now thanks to eDEX-UI, you can look like a movie hacker if you use Windows, Linux, or the Mac.

As you might expect, the program isn’t very efficient or practical, but it does actually do something. In addition to a load of system information about the CPU and network, there’s a shell, a file manager, and an onscreen keyboard, too. The app uses Electron and — on Linux — AppImage, but for a toy program like this, that may not be a problem.

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Bar Code Adds a Third Dimension

We never really thought about it before, but a traditional barcode or QR code is pretty two dimensional. A 3D barcode sounds like marketing hype but the JAB (Just Another Barcode) system adds a third dimension in the form of color.

Traditional barcodes assume you have a pretty crude sensor, but a color camera now days is no big deal, so why not take advantage? The JAB system specifies two types of symbols: a master symbol and a slave symbol. A master symbol has four finder patterns at the corner. Slave symbols dock to a master or another docked slave.

If you want to create some JABs, there’s a web interface. If you check advanced, you can change the number of colors used, the size of each “module” (colored box), and the width and height of the master symbol. You can also arrange for error correction. The grid that shows the master and slave symbols will allow you to click on any dockable slave location to create more symbols with different attributes.

You can then save the JAB image and use the scan menu item (at the top) to read the code back. It will also read from a camera.

If you are using a color camera and a computer or phone to read barcodes, this probably is something to check out. After all, you are acquiring color data, why not use it?

You might think of the barcode as something modern, but it has a long strange history going back to the 1930s. Early barcodes looked like bullseyes and were actually inspired by Morse code. We wonder how one of these would look on someone’s arm in ink?