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IBM Creates Ring Oscillator on a Single Nanotube 159

deeptrace writes "IBM has combined CMOS circuitry and a single carbon nanotube to implement a 5 stage ring oscillator. Even though the oscillator runs at just 52 MHz, they expect that it could reach the GHz range with improvements. The frequency of the current oscillator was higher than previous circuits using multiple nanotubes. IBM describes the achievement in the paper "Integrated Logic Circuit Assembled on a Single Carbon Nanotube" to be published this week in the journal Science."
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IBM Creates Ring Oscillator on a Single Nanotube

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  • A what? (Score:5, Informative)

    by Eightyford ( 893696 ) on Friday March 24, 2006 @12:30AM (#14985782) Homepage
    What the hell is a ring oscillator, you ask? Well, wikipedia says:
    A ring oscillator is a device composed of an odd number of NOT gates whose output oscillates between two voltage levels, representing true and false. The NOT gates, or inverters, are attached in a chain; the output of the last inverter is fed back into the first. The simplest ring oscillator, then, is a single inverter whose output is fed back to itself. Because a single inverter computes the logical NOT of its input, it can be shown that the last output of a chain of an odd number of inverters is the logical NOT of the first input. This final output is asserted a finite amount of time after the first input is asserted; the feedback of this last output to the input causes oscillation.

    A circular chain composed of an even number of inverters cannot be used as a ring oscillator; the last output in this case is the same as the input. However, this configuration of inverter feedback can be used as a storage element; it is the basic building block of static random access memory, or SRAM.

    A real ring oscillator only requires power to operate; above a certain threshold voltage, oscillations begin spontaneously. To increase the frequency of oscillation, two methods may be used. Firstly, the applied voltage may be increased; this increases both the frequency of the oscillation and the power consumed, which is dissipated as heat. The heat dissipated limits the speed of a given oscillator. Secondly, a smaller ring oscillator may be fabricated; this results in a higher frequency of oscillation given a certain power consumption.

    To understand the operation of a ring oscillator, one must first understand gate delay. In a physical device, no gate can switch instantaneously; in a device fabricated with MOSFETs, for example, the gate capacitance must be charged before current can flow between the source and the drain. Thus, the output of every inverter of a ring oscillator changes a finite amount of time after the input has changed. From here, it can be easily seen that adding more inverters to the chain increases the total gate delay, reducing the frequency of oscillation.
    • Can you shorten that down to about ten words?
    • What the hell is a ring oscillator, you ask?

      After reading that WP article, I think I'm still asking ;)
      • Haha, no kidding. I've never heard of it before today, and I took a few electronics classes. As far as I can tell It's basically a simple logic gate. Maybe we'll see nanotube flash memory in the near future.
        • Re:A what? (Score:2, Informative)

          by suchire ( 638146 )
          It's just a negative feedback circuit. If you inhibit yourself, then you stop producing, which stops inhibiting your own inhibition, etc. and this causes oscillation.
      • Looks, from the WP article posted above, that a ring oscillator is an odd number of NOT logic gates strung end-to-end, so that when one outputs high/1/true, the next one outputs low/0/false (the opposite), which then feeds into the next gate... when you get back to the original gate, you give it high/1/true so that it then outputs low/0/false (switches from being true to false), and the gates switch their outputs around in a circle over and over again.

        perhaps a diagram?:

        NOT gate 1 -> NOT gate 2 -
      • Re:A what? (Score:3, Interesting)

        by ncc74656 ( 45571 ) *

        What the hell is a ring oscillator, you ask?

        After reading that WP article, I think I'm still asking ;)

        After reading it, it sounds like a project from one of the Radio Shack electronics kits I had back in the day. One of the components in this kit [] was a 7400, a quad 2-input NAND gate. By tying the two inputs of a NAND gate together, it's the equivalent of an inverter. By using one or three of the gates wired in a loop, you could make a one- or three-stage ring oscillator.

        I don't recall if the do

        • I had an earlier version of that kit, it had one 7400 and less embarassing packaging.

          I remember the self-feeding oscillators had very amusing names for an 8 year old: Astable Multivibrator, only surpassed in humor-quotient by Bistable Multivibrator.

    • I belive that it might also be a sex toy from what I last heard
    • Okay, so what does it do, that is, what can it be used for?
    • by jpardey ( 569633 ) <> on Friday March 24, 2006 @02:57AM (#14986201)
      Lets see if this helps. Some people were confused...

      A ring oscillator is a device for making square waves. It uses a common component, a NOT gate. In digital logic, there are two levels, high and low (or 1 and 0, respectivly). High is usually, as far as I have seen, +5 volts, while low is 0 volts (ground).

      A NOT gate simply inverts the input. If the value is 1, it outputs 0. If the value is 0, it outputs 1. If the value is somewhere between the two, it will choose one state or the other based on some threshold voltage.

      Changing output is not instantaneous. How much time it takes, I don't know. However, it is very fast.

      I was going to draw a schematic, but I gave up on appeasing the lameness filter. So, we will use the power of imagination! Imagine one of these NOT gates hooked up to itself. It will switch on and off at a terrific rate. Put a wire on the output, and you have a square wave! Want it slower? Take another two NOT gates, and put them in the loop, so that the first one goes to the second goes to the third. Slower? Another two. If the number of NOT gates was even, the inverted signal would be uninverted by the next NOT gate, which is not what we want.

      For more control, one can use a capacitor in a certain arrangment (I'm not looking through my notes). It will take a while to charge and discharge, acting as a delay. Just don't read its voltage as the signal, or you will get a dropping bit, then a rising bit, rather than a nice clean square wave.

      Quite useful devices. I hope this clarifies things.
      • That made things a lot clearer.

        Who'd of thought your knowledge would pay off so soon?
      • I actually put together this [] earlier this month to show someone that even in a simulation environment, with every node starting at the same voltage (which should be a "stable" state, as long as it's not disturbed by outside influences), the floating point inaccuracies in the simulator are sufficient for oscillation to start spontaneously.
      • I was going to draw a schematic, but I gave up on appeasing the lameness filter.

        Now see, this underlines the drawbacks of closed-source. If we could simply have access to the technology that the GNAA and friends of the penis bird use to make their ascii art pass the lameness filter, you could have given us the schematic.

      • So far so easy. What I don't get is how this simple circuit relates to processing an audio signal through a ring oscillator. In those, for every frequency f you feed in, you get an output f+a and f-a, where a is the frequency of the ring oscillator. In other words giving in a pure sine wave of 200Hz gives you an output of, say 220Hz and 180Hz, or any other pair of values centered on the original 200Hz.

        <OT> While I'm at it, by discarding one of the signals, you get a strange-sounding frequency shifter,

    • Wow, thank god that thing wasn't something the Goatse man had attached to himself!
    • Want to make a very simple ring oscillator? Get three cheap nightlights -- the ones that turn on when it's dark -- and plug them all in on extension cords close to one another, so that each one's light is near another one's light detection cell. Congratulations: you've just made a three-unit ring oscillator. They operate at about 0.5Hz. It's also easy to make five and seven unit oscillators, of course.

      For extra credit, making NOR gates using nightlights is fairly easy but making NAND gates takes quite a
  • Some of us are not nano-physicists/EEs, so it's not clear as to what the big deal is.
  • So... (Score:1, Interesting)

    by Anonymous Coward
    I was misled to believe that the entire circuit was literally on the surface of the nanotub but from the picture in the article it looks like the nanotube is touching a couple of pads.

    Anyway, what is the significance of the low frequency? Is the ring oscillator circuit supposed to be limited in frequency only by process parasitics, so that researchers can determine the maximum frequency the process can sustain?
  • by BBCWatcher ( 900486 ) on Friday March 24, 2006 @12:34AM (#14985796)
    I'm really offended by all this IBM boosterism at Slashdot. Didn't you all hear Steve Ballmer say that IBM doesn't innovate? He's right, you know. And this carbon nanotube business is yet more evidence. IBM's work is hardly original. Carbon has been around forever. Steve Ballmer himself is made of carbon and other elements.

    Now let's talk about REAL innovation. Microsoft just announced a new facial feature pack for Office's "Clippy." Now you can customize Clippy according to your facial preferences. Options include complexion, hair style, nose shape and size, and ear/nose jewelry.

  • The oscillator works better using a single nanotube fiber than when using multiple nanotubes, according to the article. Since nanotubes carry current along the outer surface of the tube, could it be that multiple nanotubes cause the electrical quanta along the surface of each tube to interfere and degrade the signal? The article does not explain why they saw reduced performance with multiple tubes than with a single tube.

    It is important to keep in mind that 52MHz is the maximum performance achievable in t
    • by Quantum Fizz ( 860218 ) on Friday March 24, 2006 @01:14AM (#14985928)
      Since nanotubes carry current along the outer surface of the tube, could it be that multiple nanotubes cause the electrical quanta along the surface of each tube to interfere and degrade the signal?

      A carbon nanotube (CNT) is a rolled graphene plane (ie, carbon atoms in a hexagonal structure). So of course all current will be on the 'outside' of the tube, as the tube itself really only consists of the outside.

      IBM was probaby comparing single-wall nanotubes to multi-wall nanotubes. Multiwall nanotubes are composites of a bunch of concentric single-wall nanotubes. Their better results in the single-wall variety are probably due to less scattering between the graphene planes. A single CNT has a well-defined crystal structure, and is actually quite interesting. The graphene plane itself is sometimes referred to as a 'zero-bandgap insulator', where the density of states linearly goes to zero at the fermi energy (unlike an insulator or semiconductor which has a energy gap at the fermi energy, and hence cannot conduct decently like a metal).

      However through changes to the nanotube material, the performance of the nanotube may be impreved.

      They probably can get to higher frequencies. I mean, even the vibrational phonon modes of a single nanotube can be in the GHz range or higher (ie, these are the various modes of vibration that the nanotube would exhibit if you struck it, kind of like a wind chime). I don't know specifics, but I don't see why the nanotube couldn't support electronic channels with bandwidths into the GHz or even higher as well.

      Although nanotubes do have interesting characteristics different from typical metals and semiconductors. Ie, the electron-phonon interaction goes as 1/T, instead of 1/T^5 (where T is temperature). So at low temperatures there might be useful ways to couple electronic channels to vibrational modes not possible in conventional materials. Or vice versa, the phonon modes might more easily kill off electronic signals. There's alot of interesting work being done with nanotubes, and I'm sure some clever physicists and engineers will exploit these characteristics well in the near future.

  • Until they develop an imprevement we shouldn't expect the GHz range. A quick google [] doesn't provide any further information other then suggesting it is a spelling mistake.
  • Nanotubes.. (Score:2, Interesting)

    A nanotube turns on for both negative and positive voltage, and turns off somewhere in the middle

    What exactly this means?

    • Zero (Score:1, Funny)

      by Anonymous Coward
      In between positive and negative there is zero.

      Congratulations - you just qualified as a Slashdot editor !
    • Re:Nanotubes.. (Score:5, Informative)

      by Mister Transistor ( 259842 ) on Friday March 24, 2006 @12:57AM (#14985874) Journal
      Most semiconductors only turn on at a certain voltage level. For example, most silicon transistors turn on at about positive 0.7 volts. Any less than that and the trasistor won't conduct, even if you go below 0 volts to a negative voltage.

      What the person was saying about nanotubes is they will "turn on" or begin to conduct again after the voltage drops below 0 to a certain negative level. Kind of like a device that takes the absolute value of the voltage, and if it's above a certain value it conducts or switches "on".
      • I was going to make a smartass remark about being able to use "new and improved" trinary computers, with positive, negative, and neutral voltages on these transistors, but then I found out they [] already [] exist! []


        Well, at least I can welcome our ternary computing overlords!

    • Maybe I missed something, but this doesn't really look like flamebait, and I think that's a fairly harsh mod for what appears to be a simple (if badly worded) question.
  • Cool! (Score:3, Interesting)

    by Mister Transistor ( 259842 ) on Friday March 24, 2006 @12:44AM (#14985828) Journal
    Right in the middle of the 6-meter Amateur Radio band! Sounds like a nice local oscillator for an ultra-tiny nano "rig". Now, to figure out how to directly modulate it for direct FM or FSK.
  • by XXIstCenturyBoy ( 617054 ) on Friday March 24, 2006 @12:45AM (#14985837)
    Microsoft announced today that they have achieved a full annoyance oscillator and generator on a single virtual piece of bent metal.
    The findings titled "How to make Clippy more annoying" will be published next week in the Mr. Ballmer's Journal of IBM Bashing
  • Could someone please explain what are the practical uses for the ring oscillator?
    • Re:Explanation? (Score:2, Informative)

      by jackstack ( 618328 )
      FYI - a ring oscillator is just a proof of concept and there is no practical application, per se. It shows that their carbon nanotube transistor technology is well understood enough so that they can make simple logic devices (an oscillator is a bunch of inverters (NOT gate) strung together. Not long ago, slashdot had an article about a transparent ring oscillator from Oregon State Univ. Again, this was done as a stepping stone from discovering an entirely new semiconductor (this is NOT silicon, people) t
    • Re:Explanation? (Score:5, Informative)

      by jedZ ( 571869 ) on Friday March 24, 2006 @01:29AM (#14985976)
      A 5-stage ring oscillator is the hardware equivalent of a program that displays 'Hello World!'
      • That is a very neat explanation. Earlier posts described the ring oscillator as a "proof of concept" or similar, but you have successully taken advantage of a better-known concept to be both more concise and more lucid.
    • The clock on your cpu.
  • by i_am_the_r00t ( 762212 ) on Friday March 24, 2006 @01:07AM (#14985901)
    a ring Oscillator!

    On a Single Nanotube!

    crap all mighty!!!

  • by surfcow ( 169572 ) on Friday March 24, 2006 @01:08AM (#14985907) Homepage
    They're just showing off.

    It's nothing but a token ring.

  • by i_am_the_r00t ( 762212 ) on Friday March 24, 2006 @01:10AM (#14985915) the IBM labs Oh yeah! Nanotech really turns the hot chicks on
  • ...the oscillator runs at just 52 MHz...

    So I'm guessing that they have a Amateur Radio License. I wonder if they can get the nanotube to do single sideband on 6 meters.

  • by sidney ( 95068 ) on Friday March 24, 2006 @01:22AM (#14985959) Homepage
    A number of posts have asked about the significance of a 5 stage ring oscillator.

    That's the same circuit mentioned in the recent transparent IC story [] where TFA [] said

    OSU says the near-invisible integrated circuit (IC) implements a five-stage ring oscillator, a function often used for testing and demonstrating new technologies. This is analogous to when software developers write programs that simply say "hello world," as an early step in testing and debugging new computer languages.

  • by irimi_00 ( 962766 )
    Does anyone else get the impression that most people have no idea the potential for nanotech? Or maybe those that do are just schizo and nerdy.
    • Does anyone else get the impression that most people have no idea the potential for nanotech? Or maybe those that do are just schizo and nerdy.

      Most people, including the nerdy and schizo, have no real idea what nanotech is beyond maybe the latest scientific buzzword.

      In the meantime; Please don't pat yourself on the back for being a geek. That doesn't play well around here, Holmes.
  • "Hey Ethel, it looks like tube circuits are making a comeback!"
  • Applications. (Score:3, Insightful)

    by rrauwl ( 950498 ) on Friday March 24, 2006 @04:15AM (#14986410) Homepage
    Some people seem to be wondering if this is just showing off, or are there short to medium term applications for this? I think that one of the first, fairly simple applications for this is in the field of gate arrays. FPGA's, or field-programmable gate arrays, are cool devices that emulate strings of logic gates. They can be used in circuit design tasks, emulating loads on networks, and any number of geeky things. FPGA's are often considered the ugly step sister to application-specific integrated circuits, or ASIC's. Why? Because they suck more power and they're slower. People still use FPGA's a lot of the time because they're more flexible, you can change them on the fly. Now imagine an FPGA that's ultra-miniaturized, drawing almost no power, producing very little heat, and operating at amazing speeds. They need to perfect NAND or NOR gates, but once they have one of those, they can replicate them a billion times, and either of those gate types will be able to emulate every other logic gate, when placed in the right order. That's one interesting application, on the pure logic level. So it might be an exciting time, depending on how quickly they can move this out of the lab. I love this stuff.
    • Re:Applications. (Score:1, Insightful)

      by Anonymous Coward
      They need to perfect NAND or NOR gates, but once they have one of those, they can replicate them a billion times, and either of those gate types will be able to emulate every other logic gate, when placed in the right order.

      I believe one of the big problems is the replication that you're speaking of. From my understanding they don't really have a great idea of how to mass produce predictably shaped nanotubes yet. [] has a little bit of info on this too.
  • drain? (Score:2, Interesting)

    by Hawkxor ( 693408 )
    From the article: "Circuit designers understand that n-type transistors can be turned on with positive voltage applied to the drain; p-types are exactly the opposite."

    Surely they mean 'applied to the gate' (the input voltage is gate to source, the output voltage is drain to source)

    G ||_
  • Does anyone know what the maximum plate voltage is for a Nano tube?

    Also looking for a socket supplier, can't find any on E-Bay.

  • As the article states, they designed a test bed to test nanotubes. You know, benchmarks? They've designed a known circuit, where the chief variable is the performance of the nanotube. They then can try to improve the nanotube and test its performance again.

    People are missing the forest for the (exceedingly small) trees.

The unfacts, did we have them, are too imprecisely few to warrant our certitude.