Transistor Fundamentals Animated

When we were in school, every description of how transistors work was pretty dry and had a lot of math involved. We suppose you might have had a great instructor who was able to explain things more intuitively, but that was luck of the draw and statistically unlikely. These days, there are so many great videos on the Internet that explain things that even if you know the subject matter, it is fun to watch and see some of the great animations. For example [Sabin] has this beautifully animated explanation of how MOSFETs work that you can see below.

It uses the same basic graphics and style as his earlier video on bipolar transistors (second video, below) which is a great one to watch, too. In all fairness to your electronics teacher, the kind of graphics in these videos would have cost a fortune to do back in the 20th century — just watch some of the videos we talk about in some of our historical posts.

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Junk Bin Spin Coater uses Modded Case Fan

We’ve all been there: you need a specific tool or gadget to complete a project, but it’s not the kind of thing you necessarily want to fork over normal retail price for. It could be something you’re only going to use once or twice, or maybe you’re not even sure the idea is going to work and don’t want to invest too much money into it. You cast a skeptical towards the ever-growing pile of salvaged parts and wonder…

Inspiration and a dig through the junk bin is precisely how [Nixie] built this very impressive spin coater for use in his ongoing homemade semiconductor project. If you’ve never had first hand experience with a spin coater, don’t worry, not many people have. Put simply, it’s a machine that allows the user to deposit a thin layer of material on a disc by way of centrifugal force. Just place a few drops in the center of the disc, then spin it up fast enough and let physics do the rest.

[Nixie] only needs to spin up a fairly tiny disc, and realized the hub of a 40x40mm brushless case fan was just about the perfect size. A quick pass through the lathe stripped the hub of its blades and faced off the front. Once he found a tube that was the exact same diameter of the fan’s axle, he realized he could even use a small vacuum pump to hold his disc in place. A proper seal is provided by 10 and 16 mm OD o-rings, installed into concentric grooves he machined into the face of the hub.

With a way to draw a vacuum through the hub of the spinner he just needed the pump. As luck would have it, he didn’t have to wait for one to make the journey from China, as he had one of those kicking around his junk bin from a previous project. The only thing he ended up having to buy was the cheap PWM fan controller which he mounted along with the modified fan to a piece of black acrylic; producing a fairly professional looking little piece of lab equipment. Check out the video after the break for a brief demonstration of it in action.

This isn’t the first specialized piece of gear [Nixie] has produced in his quest for DIY chips. We’ve previously covered his DIY tube oven as well as his vacuum chamber complete with magnetically controlled manipulator arm.

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DIY Tube Oven Brings the Heat to Homebrew Semiconductor Fab

Specialized processes require specialized tools and instruments, and processes don’t get much more specialized than the making of semiconductors. There’s a huge industry devoted to making the equipment needed for semiconductor fabrication plants, but most of it is fabulously expensive and out of reach to the home gamer. Besides, where’s the fun in buying when you can build your own fab lab stuff, like this DIY tube oven?

A tube oven isn’t much more complicated than it sounds — it’s just a tube that gets hot. Really, really hot — [Nixie] is shooting for 1,200 °C. Not just any materials will do for such an oven, of course, and this one is built out of blocks of fused alumina ceramic. The cavity for the tube was machined with a hole saw and a homebrew jig that keeps everything aligned; at first we wondered why he didn’t use his lathe, but then we realized that chucking a brittle block of ceramic would probably not end well. A smaller hole saw was used to make trenches for the Kanthal heating element and the whole thing was put in a custom stainless enclosure. A second post covers the control electronics and test runs up to 1,000°C, which ends up looking a little like the Eye of Sauron.

We’ve been following [Nixie]’s home semiconductor fab buildout for a while now, starting with a sputtering rig for thin-film deposition. It’s been interesting to watch the progress, and we’re eager to see where this all leads.

Profiles in Science: Jack Kilby and the Integrated Circuit

Sixty years ago this month, an unassuming but gifted engineer sitting in a lonely lab at Texas Instruments penned a few lines in his notebook about his ideas for building complete circuits on a single slab of semiconductor. He had no way of knowing if his idea would even work; the idea that it would become one of the key technologies of the 20th century that would rapidly change everything about the world would have seemed like a fantasy to him.

We’ve covered the story of how the integrated circuit came to be, and the ensuing patent battle that would eventually award priority to someone else. But we’ve never taken a close look at the quiet man in the quiet lab who actually thought it up: Jack Kilby.

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Silicon Nanowires Create Flexible Photodetectors

Modern display and solar cell technologies are built with a material called Indium Tin Oxide (ITO). ITO has excellent optical transparency and electrical conductivity, and the material properties needed for integration in large-scale manufacturing. However, we’re not content with just merely “good enough” nowadays, and need better materials to build ever better devices. Graphene and carbon nanotubes have been considered as suitable replacements, but new research has identified a different possibility: nanowires.

Researchers from the Indian Association for the Cultivation of Science (IACS) and the Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) in Ireland have demonstrated a seamless silicon nanowire junction that can be used for photodetector and display technology.

Before you get lost in the jargon, let’s take a step back. A nanowire is just a very narrow length of wire, on the order of 1 nanometer across. When silicon is used at this scale, electrical charges can become stuck (called “charge trapping”), which means that the holes and electrons are separated, allowing for transistors and photovoltaics. By controlling where these holes form in the nanowire, you can create a “seamless” junction without using any dopant materials to create impurities, as is done in modern CMOS transistors

These material properties allow the functionality of a junction, but it still needs to be easily and repeatably manufactured. To solve this problem, the team put the nanowire transistors on a flexible polymer, which should enable flexible nanowire applications, such as a roll-up screen.

The first step towards a display is a simple photodetector, just consisting of a basic P-N junction, but they hope this technology will eventually be useful in “smart windows” due to the junctions’ applicability to photodetectors and cameras. Moving to emitting light for displays or creating a solar cell using this technology will probably take some time.

Do you have any experience with different materials for creating junctions? What would you do with a small, transparent photodetector? We’ve featured homebrew solar cells before, as well as creating DIY semiconductors. We’ve also seen silver nanowires for wearable circuits.

[Via IEEE Spectrum]

Robert Hall and the Solid-State Laser

The debt we all owe must be paid someday, and for inventor Robert N. Hall, that debt came due in 2016 at the ripe age of 96. Robert Hall’s passing went all but unnoticed by everyone but his family and a few close colleagues at General Electric’s Schenectady, New York research lab, where Hall spent his remarkable career.

That someone who lives for 96% of a century would outlive most of the people he had ever known is not surprising, but what’s more surprising is that more notice of his life and legacy wasn’t taken. Without his efforts, so many of the tools of modern life that we take for granted would not have come to pass, or would have been delayed. His main contribution started with a simple but seemingly outrageous idea — making a solid-state laser. But he ended up making so many more contributions that it’s worth a look at what he accomplished over his long career.

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Tiny Vacuum Chamber Arm to Help with Homemade Semiconductors

[Nixie] wants to make semiconductors at home, and that requires some unusual tools. Chief among them is a vacuum chamber to perform thin-film deposition, and true to the hacker credo his is homemade, and will soon be equipped with a tiny manipulator arm with magnetically coupled mechanical controls.

If [Nixie]’s setup looks familiar, it might be because we featured his plasma experiments a few days ago. He was a little cagey then about his goal, but he’s come clean with his desire to make his own FETs (a project that is his 2018 Hackaday Prize entry). Doing so will require not only creating stable plasmas, but also the ability to move substrates around inside the vacuum chamber. Taking inspiration from the slender and maneuverable instruments surgeons use for laparoscopic procedures, [Nixie] is working on a miniature arm that will work inside his vacuum chamber. The video below is a 3D-printed proof-of-concept model in action, and shows how the arm’s segments will be controlled by cables. What’s really interesting is that the control cables will not penetrate the vacuum chamber — they’ll be moved right through the glass wall using magnets.

We’re keen to see chips from [Nixie]’s home fab lab, but it looks like there will be a lot of cool hacks between here and there. We’ll be watching closely. Continue reading “Tiny Vacuum Chamber Arm to Help with Homemade Semiconductors”