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First Transistors Made Entirely of 2-D Materials 137

ckwu (2886397) writes "Two independent research groups report the first transistors built entirely of two-dimensional electronic materials, making the devices some of the thinnest yet. The transistors, just a few atoms thick and hence transparent, are smaller than their silicon-based counterparts, which would allow for a super-high density of pixels in flexible, next-generation displays. The research teams, one at Argonne National Laboratory and the other at the University of California, Berkeley, used materials such as tungsten diselenide, graphene, and boron nitride to make all three components of a transistor: a semiconductor, a set of electrodes, and an insulating layer. Electrons travel in the devices 70 to 100 times faster than in amorphous silicon. Such a high electron mobility means the transistors switch faster, which dictates a display's refresh rate and is necessary for high-quality video, especially 3-D video."
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First Transistors Made Entirely of 2-D Materials

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  • by slashmydots ( 2189826 ) on Wednesday May 07, 2014 @12:44PM (#46941025)
    It has a length, width, and depth. Calling it 2D is just "read me" headline-baiting which is getting more and more annoying on Slashdot lately. Here, let me correct it:
    First Transistors Made of Extremely Thin Materials
    • Re: (Score:2, Informative)

      by Penguinisto ( 415985 )

      Cross-posted w/ you, but yeah, agreed - headline fail, big-time. This doesn't even count the fact that the electrons passing through said transistor still occupy three dimensions as well.

      • Re: (Score:3, Interesting)

        by amRadioHed ( 463061 )

        Electrons are actually considered points by physicists. If they do have a size it is not currently known.

        • That does not mean they do not occupy three-dimensional space.

          • by geekoid ( 135745 )

            2 dimension objects can occupy 3d space and still be 2 dimensional.

            • How many 2 dimensional "plates" can you stack on each other before they occupy a third dimension? I would say, "quite a few". See? you can always use sufficiently complex explanations to hide behind cleverness. But if you can't answer a question a five year old can reason out, then you're just being clever. Now you will object, and say "I said CAN not MUST" and I will say, oh, aren't you a clever idiot. That's what theoretical physicists do when they aren't doing anything.
          • An intersection of a 3 dimensional plane of existence and an additional 1D one would result in a point. If string theorists are correct, the 1D plane is the vibration level of the particle somewhat similar to how time affects 3D objects despite being a separate dimension. So theoretically, it could be expressed as a 1D object in a 3D area if it's based in a 1D plane.

            Or something like that. I suck at particle physics.
            • Well, string theory is closer to religion than actual science, so it's no wonder it's hard to understand.

        • No, electrons are actually considered subatomic particles by physicists.
        • That is 100% true. They are considered a paradox where they're large enough to exist but infinitely small besides that. So their width would be expressed simply as >0. You know what bugs me is that apparently some scientists have decided, without what I consider to be a logical basis, that the singularity at the center of a black hole is not also infinitely small. It is slightly larger than the width of a neutron or quark or something like that. I don't think that's how it works.
      • Mentioned above - but electrons are not localized in a semiconductor. Many atoms share the electron - so if few enough atoms (in z direction) share the electron, the electron is 'confined' to 2 dimensions.
      • by geekoid ( 135745 )

        The headline is not fail, your understand is.
        I suggest you read Collective Behavior of Interwell Excitation in Double Quantum Wells by Larionov and Tomofev.

        Also: []

        YOU should also be aware the electrons are Zero(0) dimension objects.

    • Exactly what I was going to say. Just because it's 1 atom thick doesn't mean it's 2 dimensional.
      • It's 2 dimensional to the electrons in the transistor - not 2 dimensional in material physical dimensions. Electrons in a semiconductor occupy a large area shared between many atoms (non localized).
        • I'm really interested in this - could you dummy down the second statement? I get that electrons are flowing through a semiconducter towards the transistor, but I'm not sure I follow the "occupy a large area shared between many atoms (non localized)"? Are you referring to electrons flowing from atom to atom via their bonds? Not trying to be pedantic, I just really want to understand what you're saying (and I'm nowhere near an EE, lol).
          • Holy s***. I just spent an hour typing out a response to you, and I changed my slashdot editing options and it lost my response after saving!. I'll retype it later after my wife uses the computer.

          • I'm going to make this shorter than last time since it's now late (lost by accident) - but here goes:

            Silicon has 4 of its 8 outer band electron states filled, ([Ne]+3s2+3p2) which hybridize into 4 sp3 orbinals in a Si crystal. If you start with a single Si atom, it has discrete energy levels away from its nucleus (aka orbitals). If you bring another Si atom (which has exactly the same energy states) closer and closer, eventually these energy states interact and split (i.e. when the covalent bond is form

      • by geekoid ( 135745 )

        Yes, it does. It means specifically that in this context. Please move beyond high school physics, kthxbye.
        Let me know when you understand this: []

        then we will talk.

    • by Anonymous Coward on Wednesday May 07, 2014 @12:55PM (#46941191)

      Not the Cartesian thickness, the 2D refers to the absence of a degree of freedom: If the electrons are constrained to have no motion possible along the radial axis, that axis is considered removed from their freedom. Hence, 2D transistors

      • Thing is, the electrons are still able to move in 3-dimensional space, since they orbit the nucleus, and that orbital plane can be in any direction.

        • by Rockoon ( 1252108 ) on Wednesday May 07, 2014 @01:55PM (#46941841)

          since they orbit the nucleus

          No, they don't do that.

          Electrons exist as standing waves when coupled within an atom.

        • Re: (Score:2, Informative)

          by Anonymous Coward
          Technically, electrons do not 'orbit' the nucleus in any conventional sense of the word. We say they are in 'orbitals' (a poor choice of a term from a less enlightened time), but in reality they are better said to be in fuzzy 'clouds' where their locations are strictly probabilistic as determined by quantum mechanics.
      • 2D does not refer to an "absence of a degree of freedom". Things denoted in "*number*D" or "*number*-D"format are referring to a number of spacetime dimensions. No one in any field of math, science, or engineering ever relates degrees of motion to "D"s. Sometimes it is abbreviated DOF, but never just *number*(-)D as that is reserved for dimensions.
      • I originally thought this meant a type of transistor that did not use layers. Hoever it turns out this isn't true either, there are several layers to these transistors. Very thin layers of course, but there is a definite third axis that is vital to the operation.

    • Materials scientists use "two-dimensional" to describe graphene and similar materials. These are materials that consist of essentially a single molecular/atomic layer.
    • by timeOday ( 582209 ) on Wednesday May 07, 2014 @01:16PM (#46941455)
      What percent of discussion on slashdot goes down in flames over semantic quibbles having nothing to do with the substance of the issue at hand?
      • by Anonymous Coward

        Maybe have a big sign at the top, "Pedants this way ->"

      • You CAN theoretically make an area of space that only supports 2 dimensions. Nobody can or has done it but it's possible, in theory. You just compress 3D space until it collapses then occupy the resulting space with only 1D and 2D objects. Simple, lol.

        So it's not an issue of word choice, it's an issue of a COMPLETELY scientifically incorrect title written by either a moron or a social engineer to grab views, which is ruining slashdot. The complaints are actually double on topic then, aren't they? The
      • What percentage of the discussion on Slashdot goes down in flames over semantic quibbles having nothing to do with the substance of the issue at hand?


    • KInd of a stupid thing to say. I suggest you investigate what a physicist means by two dimensional. Such as in "surface phenomena". Essential this means that the physics of 2D QFT and 2D statistical mechanics apply to what is happening on these semiconductors.

    • Hear Hear!
    • In a semiconductor, electrons are not localized. They exist as a wave -- usually mathematically as a wave packet to compromise between a wave and a particle (it is both) -- this wave can be very easily several nanometers. Additionally, electrons diffuse around a semiconductor (they are not bound to one atom) - and this diffusion length is much much larger than a few nm. When a material is just a couple of nanometers, the electrons cannot (statistically) move vertically, and the material is considered 2D
  • "The transistors, just a few atoms thick and hence transparent,"

    Sorry, but "a few atoms thick" still gives it all three axes in Cartesian space, no matter how small any given axis may be. Hell, even "one atom thick" qualifies as three-dimensional.

    Pedant Headline Fail, eh?

    • Pedant Headline Fail, eh?

      Just keepin' 'em honest - if they can do some kind of quantum tunneling of electrons, I'd be willing to forgive the deBroglie height of their waves and call it 2D, if there's to be any useful application of such a term within our view of the universe.

    • by Kenja ( 541830 )
      They are made from an infinite number of 2D layers!
    • by Anonymous Coward

      It depends. There are regimes where the transport can be considered 2D (ie. the density of states function is characteristic of a 2D system).

      It is not always simply the dimensionality of the physical device that is relevant.

    • by NoKaOi ( 1415755 )

      "The transistors, just a few atoms thick and hence transparent,"

      Sorry, but "a few atoms thick" still gives it all three axes in Cartesian space, no matter how small any given axis may be. Hell, even "one atom thick" qualifies as three-dimensional.

      Pedant Headline Fail, eh?

      Although the whole thing is a few atoms thick, each individual material is only one atom thick. It is a few atoms thick because it consists of 3 different materials, each layer of which is 1 atom thick. Click on the article and there's a pretty picture at the top for you. While I dislike the term 2-D (why can't they just call it one atom thick?) because a single atom obviously has thickness, as far as electrons are concerned there are only 2 dimensions that matter. The term relates to electron transport

      • An atom is not 2-d. 3 layers of atoms can not possibly be 2-d.

        An atom is composed of sub-atomic particles which are also NOT 2-d.

        2-d, in our universe, does not exist, its a virtual concept used to describe other abstract things.

        They (nor you) get to redefine it to mean something different to suit your sensationalizing agenda.

        Using improper terms brings doubt to the whole paper and everything it says. We use specific meanings of words so that we understand the meaning, if you use your own meaning for thing

        • The dimensionality of the object can be higher than the degrees of freedom. For reference by analogy, see gimbals, which allow representation of arbitrary axes in n-dimensions, but are subject to gimbal lock, where a change in one axis may be represented by a substitution of a change in another axis, eliminating a degree of freedom (not to be confused with dimension).

    • by maird ( 699535 )
      I wondered about that one for a bit but no-one said the transistors were 2D, only that the materials the transistors were made were two dimensional. The transistors themselves consist of layers of these materials, each one atom thick giving the transistor itself three-dimensions: "First Transistors Made Entirely of 2-D Materials". Underscore materials not transistors. Every atom in each layer can be referenced by it's position relative to any other position in the layer using only two dimensions (left a cou
    • by geekoid ( 135745 )

      So may physics ignorant people on slashdot.

  • I am impressed, but I was hoping to be stunned.

  • by wjcofkc ( 964165 ) on Wednesday May 07, 2014 @12:58PM (#46941217)
    having or appearing to have length and breadth but no depth.

    According some of the definitions of two-dimensional that I am reading here, there is no such thing as two-dimensional outside of a few popular thought experiments in theoretical physics.
    appearing to have - This is why it is not incorrect to call a sheet of paper two-dimensional.
    • But a piece of paper appears to have three dimensions.

      Even when you look at it edge-on.

      So it is still totally incorrect to call a piece of paper two-dimensional.

      • by wjcofkc ( 964165 )
        Your really grasping there.
        • No, he's not, not even a little. You said it yourself, there is no such thing as 2-d in our universe outside of thought experiments.

          That doesn't mean you get to redefine it so that it magically does exist in our universe.

          Language only works because we understand the meaning of the words being used, when you randomly redefine them to suit your own personal agenda the whole thing breaks down.

          If they can't even use the proper terms, it makes the whole paper suspect.

          • by wjcofkc ( 964165 )
            I didn't define it. I got that out of a dictionary. I guess what you're not understanding is that to describe something physical as two-dimensional, we are referring to perception through our senses. It is a depth deficit, not a lack. Here are a couple more definitions:

            Two Dimensional refers to objects or pictures that lack the expected range or depth.

            Lacking the expected range or depth; not designed to give an illusion or depth

            So when you refer to something like a piece of paper as being three-dim
      • by c4320n ( 2551122 )
        Except people do call pieces of paper (and, more commonly, things drawn on them) 'two dimensional'. With great frequency. It's entirely consistent to call something five atoms thick, where the axis perpendicular to its plane is pretty much entirely irrelevant to its design, 'two dimensional'.
        • by maird ( 699535 )
          Indeed, most drawings I can think of can be reproduced by moving the drawing device using only two directional references regardless of how thick the material placed on the paper is. Therefore, the drawing is two dimensional in a real sense even though it is simultaneously three dimensional in terms of deposit of crayon, pencil, chalk, ink, etc.
    • Re: (Score:2, Funny)

      by radarskiy ( 2874255 )

      Why try to explain actual engineering to a bunch of typists?

    • The transistors as described only work because of the 3 dimensional properties of having layers. There are indeed transistors that are two dimensional in the sense that no wire or layer needs to cross another wire or layer, but that's not true in this case. What they've done is take somewhat normal transistors and made them really really thin with new materials (two of the three layers are only one atom thick). So building a circuit from such material would require applying layers in certain patterns. T

  • by koan ( 80826 )

    The rise of the disposable video newspaper, and what I really want video wall paper.

  • On a measurement level, they are 3 dimensional as nothing in our universe lacks having those 3 dimensions.
    Of course, you could never discern that thickness without some highly specialized super sensitive devices.

    Then there's the whole effective or design thing going on there. That map you look at when you get lost, it's considered 2d. Not because the ink and paper is composed of atoms and are actually 3d, but rather because the information and design of it's display is only on 2 dimensions. Ever see a 3 dim
  • I know very little about display tech, but is display refresh rate really dictated by transistor switching speed? In any event, solid-state amplifiers can extend well into the GHz range, and display refresh rate is sub-kHz. I think rise-times of existing transistors are measured in ns, not ms.

    I understand that high framerates at many megapixels can be computationally expensive, but I wouldn't call that refresh rate. Are talking display tech or graphics card tech here?
  • Dear Earth,

    Due to budget cuts related to the long and intense war with Satan, I am canceling one of the spacial dimensions. Thus, please re-engineer your technology for 2D instead of 3D.

    My apologies for any inconveniences this may cause, but we must all make sacrifices to win this difficult war.


  • Lives I tell you!

  • Electrons travel in the devices 70 to 100 times faster than in amorphous silicon.

    It's a good thing that we make our transistors out of monocrystalline silicon then! Are you kidding me?! My grandmother can run down the corridor 100 faster than electrons in amorphous silicon.

    • "make our transistors out of monocrystalline silicon"

      Not the transistors on LCD displays, which are specifically referenced here.

      The objective is to layer 2-d devices made with good materials over the display rather than making crappy devices directly on the amorphous silicon.

  • FFS (Score:2, Funny)

    by Okonomiyaki ( 662220 )

    Shut up. All of you.

  • I was like, "No they weren't - the first transistors were bulky as hell! []"

  • I agree it is not 2D BUT I am thrilled at the progress in the technology.
  • So, they'll only cost two thirds the price?

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