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Y-junction Nanotubes

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  • Ihsan Hariadi
    It is interesting to realize that Carbon Nanotubes could behave as either semiconductor or metal. The article below, among other, reports the possibility of
    Message 1 of 10 , Nov 1, 2000
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      It is interesting to realize that Carbon Nanotubes could behave
      as either semiconductor or metal. The article below, among other,
      reports the possibility of building so-called "Y-junction" Carbon
      nanotubes to form

      a Metal-Semiconductor-Metal contact

      Is there any possibility to dope the Carbon Nanotube semiconductors
      to form both n-type and and p-type ones, and hence, to realize
      p-n junction, or more complex devices, ...? Thankyou.

      << ihsan >>

      ----------------------------------------------------------
      From : "Danial Irfachsyad" < d.irfachsyad@... >
      Date : Thu, 26 Oct 2000 17:40:52 -0000
      Subject: Nanotechnology: Crossroads in carbon
      ----------------------------------------------------------


      Nature 26 Oct 2000:

      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      Nanotechnology: Crossroads in carbon
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      Liesbeth Venema


      The smallest electronic device could be based on just one single
      molecule. Carbon nanotubes flexible, hollow nanowires with
      versatile electronic properties have already proven themselves as
      miniature diodes and transistors. In a paper in Applied Physics
      Letters (77, 2530-2532, 2000), C. Rao and colleagues from the
      Jawaharlal Nehru Centre for Advanced Scientific Research in India
      now demonstrate an efficient method for synthesizing a more
      advanced structure from carbon nanotubes: Y-junctions. Such
      structures could be used in new types of molecular devices.

      Carbon nanotubes are known for their remarkable property to be
      either a semiconductor or a metal, depending on their diameter
      and the winding of the carbon sheet from which the nanowire is
      made. A sharp bend in a nanotube can actually be thought of as a
      junction between two nanotubes with different electronic
      behaviour and so provide a transition from semiconductor to metal
      over a distance of just a few nanometres. Such sharply bent
      tubes have already been used as molecular diodes. But scientists
      are always on the lookout for more complex structures based on
      carbon nanotubes. A Y-junction can be thought of as a connection
      between three different carbon nanotubes, which could form, for
      example, a microscopic metal-semiconductor-metal contact.

      In previous attempts to construct complex junctions, two
      nanotubes have been crossed or Y-shaped templates have been used
      to laboriously mould a junction from a single nanotube. A simple
      method to produce carbon nanotubes is pyrolysis of organic
      molecules. In this process, carbon-containing molecules are
      decomposed at high temperatures, using appropriate catalysts.
      Rao and co-workers have finely tuned this method to create their
      Y-tubes, with a 70% yield. They decompose nickelocene, an organic
      molecule containing a nickel atom, along with another organic
      molecule, thiophene, at a temperature of 1,273 K. An electron
      microscope image of the product (shown here) reveals that the Y-
      shaped nanotubes are multi-walled and have an outer diameter of
      about 40 nanometres. The angle between the upper arms is almost
      90°.

      One of the current objectives in nanotube synthesis is to have
      control over the electronic properties of the end product.
      Although the electronic structure of these Y-junctions is not
      known exactly, initial measurements by Rao and co-workers show
      that their Y-junctions can behave like diodes. This work is still
      preliminary, but it will inspire further studies into making
      three-point nanotube junctions with specific semiconductor-metal
      transitions. Such molecular junctions will be useful building
      blocks in the continuing miniaturization of complex electronic
      devices.

      --= oOo =--
    • Bruce Bombere
      One thing that occured to me from reading the article was the old drum random access memory storage devices where magnetic donuts with three wires passing
      Message 2 of 10 , Nov 1, 2000
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        One thing that occured to me from reading the article was the old
        drum random access memory storage devices where magnetic donuts with
        three wires passing through each, two wires each carrying half charge
        and one sensor wire. This same "donut" arrangement might be contrived
        on a molecular level for random memory storage given the semiconductor
        and metal characteristics of carbon nanotubes.

        Ihsan Hariadi wrote:
        >
        > It is interesting to realize that Carbon Nanotubes could behave
        > as either semiconductor or metal. The article below, among other,
        > reports the possibility of building so-called "Y-junction" Carbon
        > nanotubes to form
        >
        > a Metal-Semiconductor-Metal contact
        >
        > Is there any possibility to dope the Carbon Nanotube semiconductors
        > to form both n-type and and p-type ones, and hence, to realize
        > p-n junction, or more complex devices, ...? Thankyou.
        >
        > << ihsan >>
        >
        > ----------------------------------------------------------
        > From : "Danial Irfachsyad" < d.irfachsyad@... >
        > Date : Thu, 26 Oct 2000 17:40:52 -0000
        > Subject: Nanotechnology: Crossroads in carbon
        > ----------------------------------------------------------
        >
        > Nature 26 Oct 2000:
        >
        > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        > Nanotechnology: Crossroads in carbon
        > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        >
        > Liesbeth Venema
        >
        > The smallest electronic device could be based on just one single
        > molecule. Carbon nanotubes flexible, hollow nanowires with
        > versatile electronic properties have already proven themselves as
        > miniature diodes and transistors. In a paper in Applied Physics
        > Letters (77, 2530-2532, 2000), C. Rao and colleagues from the
        > Jawaharlal Nehru Centre for Advanced Scientific Research in India
        > now demonstrate an efficient method for synthesizing a more
        > advanced structure from carbon nanotubes: Y-junctions. Such
        > structures could be used in new types of molecular devices.
        >
        > Carbon nanotubes are known for their remarkable property to be
        > either a semiconductor or a metal, depending on their diameter
        > and the winding of the carbon sheet from which the nanowire is
        > made. A sharp bend in a nanotube can actually be thought of as a
        > junction between two nanotubes with different electronic
        > behaviour and so provide a transition from semiconductor to metal
        > over a distance of just a few nanometres. Such sharply bent
        > tubes have already been used as molecular diodes. But scientists
        > are always on the lookout for more complex structures based on
        > carbon nanotubes. A Y-junction can be thought of as a connection
        > between three different carbon nanotubes, which could form, for
        > example, a microscopic metal-semiconductor-metal contact.
        >
        > In previous attempts to construct complex junctions, two
        > nanotubes have been crossed or Y-shaped templates have been used
        > to laboriously mould a junction from a single nanotube. A simple
        > method to produce carbon nanotubes is pyrolysis of organic
        > molecules. In this process, carbon-containing molecules are
        > decomposed at high temperatures, using appropriate catalysts.
        > Rao and co-workers have finely tuned this method to create their
        > Y-tubes, with a 70% yield. They decompose nickelocene, an organic
        > molecule containing a nickel atom, along with another organic
        > molecule, thiophene, at a temperature of 1,273 K. An electron
        > microscope image of the product (shown here) reveals that the Y-
        > shaped nanotubes are multi-walled and have an outer diameter of
        > about 40 nanometres. The angle between the upper arms is almost
        > 90°.
        >
        > One of the current objectives in nanotube synthesis is to have
        > control over the electronic properties of the end product.
        > Although the electronic structure of these Y-junctions is not
        > known exactly, initial measurements by Rao and co-workers show
        > that their Y-junctions can behave like diodes. This work is still
        > preliminary, but it will inspire further studies into making
        > three-point nanotube junctions with specific semiconductor-metal
        > transitions. Such molecular junctions will be useful building
        > blocks in the continuing miniaturization of complex electronic
        > devices.
        >
        > --= oOo =--
        >
        >
        > The Nanotechnology Industries mailing list.
        > "Nanotechnology: solutions for the future."

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      • Bryan & Lois Swinney
        Bruce Bombere wrote: One thing that occured to me from reading the article was the old drum random access memory storage devices where
        Message 3 of 10 , Nov 9, 2000
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          Bruce Bombere <xenuxenu@...> wrote:


          "One thing that occured to me from reading the article was the old
          drum random access memory storage devices where magnetic donuts with
          three wires passing through each, two wires each carrying half charge
          and one sensor wire. This same "donut" arrangement might be contrived
          on a molecular level for random memory storage given the semiconductor
          and metal characteristics of carbon nanotubes."

          The devices Bruce refers to were actually magnetic core memories. The
          three (sometimes more) electrically isolated conductors were threaded
          through a small ferrite donut called a core. Each of two electrical
          conductors was electrically charged and thereby producing a magnetic flux
          which either magnatized or demagnatized the ferrite core. Large quantities
          of electrical current were required to produce the magnetic flux. By todays
          standards, magnetic core memories were very slow when compared to
          semiconductor memory of that day and required several magnitudes of more
          electrical power to peform the same work of the semicoductor memory. The
          main strength of the core memory was its ability to retain its "memory"
          when electrical power was lost.

          To reproduce the same core memory technology, using carbon nanotubes, would
          require laying three or more electrically isolated conductors through the
          center of the carbon nanotube, while maintaining their electrical isolation
          from each other. One of the present limitations to developing faster and
          smaller semiconductor memories is the width (one atom's width) of the
          semiconductor electrical signal leads between the various components. Even
          with the breakthroughs of nanotechnology, it presently is inconceiveable
          how even smaller (by several magnitudes) isolated semiconductor leads may
          be developed. Perhaps (just perhaps) some day we may have sub-atomic
          particle isolated electrical leads - who knows????? Or perhaps several
          carbon nanotubes (with a single isolated electrical lead through each of
          them) placed adjacent to one another (within the influience of the others
          magnetic flux) could be used to constitute one magnetic "bit"????? Food
          for thought!

          Bryan Swinney
        • Christopher J. Phoenix
          ... 1) It s called core , not drum . Drum is similar to disk, except... well, it s a drum. 2) Core stored information by changing the magnetic properties of
          Message 4 of 10 , Nov 9, 2000
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            At 01:24 PM 11/1/00 -0500, Bruce Bombere wrote:
            >One thing that occured to me from reading the article was the old
            >drum random access memory storage devices where magnetic donuts with
            >three wires passing through each, two wires each carrying half charge
            >and one sensor wire. This same "donut" arrangement might be contrived
            >on a molecular level for random memory storage given the semiconductor
            >and metal characteristics of carbon nanotubes.

            1) It's called "core", not "drum". Drum is similar to disk, except... well,
            it's a drum.

            2) Core stored information by changing the magnetic properties of the donut.
            Magnetism doesn't work so well at the nanoscale. How do you want to store
            the state? You could store it electrostatically, by tunnelling an electron
            to a nearby charge carrier that would then affect the V/I characteristics of
            the tube. This would just be a smaller implementation of an existing idea.
            You could store it mechanically by bending the tube. This has been
            demonstrated--crossed tubes moved electrostatically, sticking by VdW and
            coming apart in response to different V levels. Cool stuff! But I don't
            see any way to use magnets.

            Chris
            --
            Chris Phoenix cphoenix@... http://www.best.com/~cphoenix
            Work (Reading Research Council): http://www.dyslexia.com
            Is your paradigm shift automatic or stick?
          • Bruce Bombere
            ... My guess would be electrostatic, but something more than film, more like intercommunicating layers. This is a learning experience for me, why things don t
            Message 5 of 10 , Nov 9, 2000
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              Christopher J. Phoenix wrote:
              >
              > At 01:24 PM 11/1/00 -0500, Bruce Bombere wrote:
              > >One thing that occured to me from reading the article was the old
              > >drum random access memory storage devices where magnetic donuts with
              > >three wires passing through each, two wires each carrying half charge
              > >and one sensor wire. This same "donut" arrangement might be contrived
              > >on a molecular level for random memory storage given the semiconductor
              > >and metal characteristics of carbon nanotubes.
              >
              > 1) It's called "core", not "drum". Drum is similar to disk, except... well,
              > it's a drum.
              >
              > 2) Core stored information by changing the magnetic properties of the donut.
              > Magnetism doesn't work so well at the nanoscale. How do you want to store
              > the state? You could store it electrostatically, by tunnelling an electron
              > to a nearby charge carrier that would then affect the V/I characteristics of
              > the tube. This would just be a smaller implementation of an existing idea.
              > You could store it mechanically by bending the tube. This has been
              > demonstrated--crossed tubes moved electrostatically, sticking by VdW and
              > coming apart in response to different V levels. Cool stuff! But I don't
              > see any way to use magnets.
              >
              > Chris
              > --


              My guess would be electrostatic, but something more than film,
              more like intercommunicating layers. This is a learning experience
              for me, why things don't translate from one level of scale to another.

              But your suggestion of the mechanical switching system reminds
              me of the early UNIVAC. I think that maybe it would be best for me
              to abandon my retro approaches new science. Thanks for helping
              me along with my understanding of nanotechnology.

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            • Ed Minchau
              In Scientific American s Mathematical Games column, April of I can t remember which year, they presented an April Fool s joke about the island of Apraphul. On
              Message 6 of 10 , Nov 10, 2000
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                In Scientific American's Mathematical Games column, April of I can't remember which year, they presented an April Fool's joke about the island of Apraphul. On the island they had constructed a computer of ropes, pulleys, and levers - a purely mechanical computer. They also presented designs for various logic gates (NAND, NOR, etc).

                On the macroscale, the Apraphul computer was ludicrous; friction would grind such a computer to a halt. But, how about on the nanoscale? A bit could be represented by say a nanotube, and the state of the bit could be encoded in the orientation of the tube in space with respect to some arbitrary reference.

                :) ed


                ________________________________________________________________________

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              • Bruce Bombere
                ... Yep, there are likely applications for tubule flexion for switching. I am still amazed at the idea of storing data on the shell of a single atom, perhaps
                Message 7 of 10 , Nov 11, 2000
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                  Ed Minchau wrote:
                  >
                  > In Scientific American's Mathematical Games column, April of I can't remember which year, they presented an April Fool's joke about the island of Apraphul. On the island they had constructed a computer of ropes, pulleys, and levers - a purely mechanical computer. They also presented designs for various logic gates (NAND, NOR, etc).
                  >
                  > On the macroscale, the Apraphul computer was ludicrous; friction would grind such a computer to a halt. But, how about on the nanoscale? A bit could be represented by say a nanotube, and the state of the bit could be encoded in the orientation of the tube in space with respect to some arbitrary reference.
                  >
                  > :) ed
                  >

                  Yep, there are likely applications for tubule flexion for switching.
                  I am still amazed at the idea of storing data on the shell of a single
                  atom, perhaps switching sequences can similarly be stored.

                  I've long been a fan of Rube Goldberg machinery, so, the Apraphul
                  computer
                  doesn't seem too far fetched.

                  http://www.rube-goldberg.com/

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                • Christopher J. Phoenix
                  ... grind such a computer to a halt. But, how about on the nanoscale? A bit could be represented by say a nanotube, and the state of the bit could be encoded
                  Message 8 of 10 , Nov 11, 2000
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                    At 10:28 PM 11/10/00 -0800, Ed Minchau wrote:
                    >On the macroscale, the Apraphul computer was ludicrous; friction would
                    grind such a computer to a halt. But, how about on the nanoscale? A bit
                    could be represented by say a nanotube, and the state of the bit could be
                    encoded in the orientation of the tube in space with respect to some
                    arbitrary reference.

                    Drexler has described "rod-logic" computers for years. See Nanosystems for
                    example. They have some incredible size and power consumption figures... a
                    1000-MIPS computer (single CPU) could fit in a cubic micron and draw 60 nW.

                    Chris
                    --
                    Chris Phoenix cphoenix@... http://www.best.com/~cphoenix
                    Work (Reading Research Council): http://www.dyslexia.com
                    Is your paradigm shift automatic or stick?
                  • Christopher J. Phoenix
                    ... Get a copy of Nanosystems. It has some great tables and explanations in chapter 2. The rest of the book is really interesting too. You can ignore the
                    Message 9 of 10 , Nov 11, 2000
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                      At 09:42 PM 11/9/00 -0500, Bruce Bombere wrote:
                      > My guess would be electrostatic, but something more than film,
                      >more like intercommunicating layers. This is a learning experience
                      >for me, why things don't translate from one level of scale to another.

                      Get a copy of Nanosystems. It has some great tables and explanations in
                      chapter 2. The rest of the book is really interesting too. You can ignore
                      the formulas and still get most of the information, then go back and learn
                      the formulas you need when it's time to do engineering.

                      > But your suggestion of the mechanical switching system reminds
                      >me of the early UNIVAC. I think that maybe it would be best for me
                      >to abandon my retro approaches new science.

                      No, don't do that! Taking ideas from one place and trying to solve
                      different problems with them is a good way to be creative. And after all,
                      it's possible that I was wrong about magnets, anyway. Each atom of iron is
                      a magnet, and I really don't know how sensitive buckytube electrical
                      properties are to nearby magnetic fields. My guess is that it would be hard
                      to to switch the magnetic state of the atom by producing a magnetic field by
                      running current through the tubes (thermal noise would be a lot "stronger")
                      but I haven't done the math and there might be low-temperature applications.
                      Or you could use a different switching mechanism.

                      Keep thinking!

                      Chris
                      --
                      Chris Phoenix cphoenix@... http://www.best.com/~cphoenix
                      Work (Reading Research Council): http://www.dyslexia.com
                      Is your paradigm shift automatic or stick?
                    • Bruce Bombere
                      ... Yes, this URL has several articles on metals and localized electrical phenomena. http://www.ifm.liu.se/Theophys/projects.html The suggestion that computers
                      Message 10 of 10 , Nov 11, 2000
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                        Christopher J. Phoenix wrote:
                        >
                        > At 09:42 PM 11/9/00 -0500, Bruce Bombere wrote:
                        > > My guess would be electrostatic, but something more than film,
                        > >more like intercommunicating layers. This is a learning experience
                        > >for me, why things don't translate from one level of scale to another.
                        >
                        > Get a copy of Nanosystems. It has some great tables and explanations in
                        > chapter 2. The rest of the book is really interesting too. You can ignore
                        > the formulas and still get most of the information, then go back and learn
                        > the formulas you need when it's time to do engineering.
                        >
                        > > But your suggestion of the mechanical switching system reminds
                        > >me of the early UNIVAC. I think that maybe it would be best for me
                        > >to abandon my retro approaches new science.
                        >
                        > No, don't do that! Taking ideas from one place and trying to solve
                        > different problems with them is a good way to be creative. And after all,
                        > it's possible that I was wrong about magnets, anyway. Each atom of iron is
                        > a magnet, and I really don't know how sensitive buckytube electrical
                        > properties are to nearby magnetic fields. My guess is that it would be hard
                        > to to switch the magnetic state of the atom by producing a magnetic field by
                        > running current through the tubes (thermal noise would be a lot "stronger")
                        > but I haven't done the math and there might be low-temperature applications.
                        > Or you could use a different switching mechanism.
                        >
                        > Keep thinking!
                        >
                        > Chris
                        > --

                        Yes, this URL has several articles on metals and localized electrical
                        phenomena.

                        http://www.ifm.liu.se/Theophys/projects.html

                        The suggestion that computers might disappear and be incorporated
                        into fiber-optic strands is interesting.

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