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.
Continue reading “Profiles in Science: Jack Kilby and the Integrated Circuit”
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]
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.
[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”
The idea of making your own semiconductors from scratch would be more attractive if it weren’t for the expensive equipment and noxious chemicals required for silicon fabrication. But simple semiconductors can be cooked up at home without anything fancy, and they can actually yield pretty good results.
Granted, [Simplifier] has been working on the method detailed in the video below for about a year, and a look at his post on copper oxide thin-film solar cells reveals a meticulous approach to optimize everything. He started with regular window glass, heated over a propane burner and sprayed with a tin oxide solution to make it conductive while remaining transparent. The N-type layer was sprayed on next in the form of zinc oxide doped with magnesium. Copper oxide, the P-type layer, was electroplated on next, followed by a quick dip in copper sulfide to act as another transparent conductor. A conductive compound of sodium silicate and graphite was layered on the back to form the electrical contacts. The cell worked pretty well — 525 mV open circuit voltage and 6.5 mA short-circuit current. Not bad for home brewed.
If you want to replicate [Simplifier]’s methods, you’ll find his ample documentation of his site. Of course, if you yearn for DIY silicon semiconductors, there’s a fab for that, too.
Continue reading “Home Brew Solar Cells for the Chemically Curious”
Building a circuit to blink an LED is the hardware world’s version of the venerable “Hello, world!” program — it teaches you the basics in a friendly, approachable way. And the blinky light project remains a valuable teaching tool right up through the hardware wizard level, provided you build your own LEDs first.
For [emach1ne], the DIY LED was part of a Master’s degree course and began with a slice of epitaxial wafer that goes through cleaning, annealing, and acid etching steps in preparation for photolithography. While gingerly handling some expensive masks, [emach1ne] got to use some really cool tools and processes — mask aligners, plasma etchers, and electron beam vapor deposition. [emach1ne] details every step that led to a nursery of baby LEDs on the wafer, each of which was tested. Working arrays were cut from the wafer and mounted in a lead frame, bonded with gold wires, and fiat lux.
The whole thing must have been a great experience in modern fab methods, and [emach1ne] should feel lucky to have access to tools like these. But if you think you can’t build your own semiconductor fab, we beg to differ.
You think you’ve got it going on because you can wire up some eBay modules and make some LEDs blink, or because you designed your own PCB, or maybe even because you’re an RF wizard. Then you see that someone is fabricating semiconductors at home, and you realize there’s always another mountain to climb.
We were mesmerized when we first saw [Sam Zeloof]’s awesome garage-turned-semiconductor fab lab. He says he’s only been acquiring equipment since October of 2016, but in that short time he’s built quite an impressive array of gear; a spin-coating centrifuge, furnaces, tons of lab supplies and toxic chemicals, a turbomolecular vacuum pump, and a vacuum chamber that looks like something from a CERN lab.
[Sam]’s goal is to get set up for thin-film deposition so he can make integrated circuits, but with what he has on hand he’s managed to build a few diodes, some photovoltaic cells, and a couple of MOSFETs. He’s not growing silicon crystals and making his own wafers — yet — but relies on eBay to supply his wafers. The video below is a longish intro to [Sam]’s methods, and his YouTube channel has a video tour of his fab and a few videos on making specific devices.
[Sam] credits [Jeri Ellsworth]’s DIY semiconductor efforts, which we’ve covered before, as inspiration for his fab, and we’re going to be watching to see where he takes it from here. For now, though, we’d better boost the aspiration level of our future projects.
Continue reading “The Fab Lab Next Door: DIY Semiconductors”