Friday, December 30, 2016

Are These The Thinnest Wires Physically Possible?

That's what the folks at the Stanford Linear Accelerator Center (SLAC) are saying.  This week's EE Times picks up the story. 
SLAC has demonstrated what it claims are the thinnest possible nanowires — just three-atoms thin. SLAC's process uses the smallest possible fragment of a diamond — called a diamondoid — as an insulating shell into which the copper/sulfur atoms self-assemble. The world's smallest diamondoid — an adamantane with just a 10-atom circumference — allows a three atom conductive core to self-assemble to any length.
Seems tough to imagine they can get much thinner than three atoms, with a 10-atom insulating sheath on it.  I'm sort of surprised that with only three atoms across the nanowires exhibit the macroscopic properties of ordinary insulated wire, and not bizarre quantum superposition of properties.  You're not going to be using your Stripmasters on these anytime soon.

The paper is published in Nature Materials (paywall for worthwhile content) and focuses on the self-assembling properties that combine these small pieces of conductor, each bound to an insulating particle of diamond (pure carbon).  The conducting portion is copper sulfur atoms, shown here as sulfur in yellow and copper in reddish brown.  The gray scaffolding is the carbon atoms - the diamond.  
The key here is literally finding the right ingredients.  Then they're put in a vessel on the desktop and the experimenter just sits and watches as the wires self-assemble.
The simple "beaker" process used to form the nanowires, created by the SLAC researchers, merely involves putting the correct materials in solution with the diamondoids and within a half-hour, the nanowires begin self-assembling as long as the materials last. 
The nanowires even help the experimenters out after the "watch the magic" phase.  They diamondoids have a high attraction to each other and so it's easy to gather them.  
The diamondoids themselves are found naturally occurring in certain petroleum products, making the process relatively inexpensive to execute. Stanford researchers have already found other uses for the diamanoids in improving electron microscope images and in the construction of tiny electronic devices.  Sulfur and copper are both abundant, cheap components, so this looks like it could be an economical way to manufacture wires for even smaller semiconductors than are currently in development.  The team has already fabricated similar nanowires using cadmium for optoelectronics applications, zinc nanowires for solar applications and piezoelectric materials for energy harvesters.


  1. This is "neat"!
    Seems "physics" is getting down to a re-definition of "wire" ... an enforced and directed path of electron movement. Since electrons move in "space" between atoms anyway, is electronics moving into the meta-physical realm? (or has it always been there?) Maybe we get rid of "wires" (conduction paths) altogether and use fields - at that scale - for electron confinement (but then, would the field generators be part of the "wire"?)

    In practice though, while moving electrons along "wires" of these dimensions can be considered astounding, how do they interface with "something" at that scale? Biggest problem with ICs is the outside world interface. I can build circuits which fit quite comfortably on the tip of a mechanical pencil - a 0.5 mm pencil tip is huge ... but the connection to "the world" is even larger in comparison. On the other hand, large scale memories, etc would greatly benefit even if the outside connections were large.

    Is the field moving back towards plasma streams such as vacuum tubes? How does one make a transistor at these scales? After all, it's the concept of gain that defines electronics vs particle physics. Tbytes on a pencil tip ... still need a gain element or switch of some sort though. Disclaimer: I'm an "analog" guy and obsolete. Where there's a will (and funding), there's a way.

    Questions to be explored, not comments negating the accomplishment.

    Something still absolutely fascinating about this stuff even after many decades of working with it (built my first VTVM in 1963 at an age that wouldn't be allowed these days. A youngster working unsupervised with 400V??? Thank you Heathkit). Makes me (sometimes) want to go back to work on another Phuud.


    1. I think it's just a very neat concept. I puzzle over how they measure conductivity of wires 10 atoms across. They sure don't grab it with gator clips! I saw a transistor that was considered the world's smallest that was based on nanotubes, within the last month or two. I think it was around 1 nm across, but the transistor action was along its length, not across it. "How do you connect to the outside world?" has to get more important as device geometries approach the size of a few atoms. The 4 nm devices everyone is talking about are about 36 silicon atoms across. What connects to something that small? Every surface is irregular at that scale.

      There are integrated vacuum devices in the labs, though none are commercial yet (that I know of), and a lot of people speculate the triode is coming back. Only without a heater and filament!

  2. The last sentence mentions that the researchers have changed the composition of the nanowires. If we change the composition to get maximum strength, can we get self assembling cables strong enough for the beanstalk space elevator?

  3. Happy New Year to all