nanotechnology - wayne state glawes/nano.pdf · q: what is nanotechnology? narrow...

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  • Nanotechnology Gavin Lawes

    Department of Physics and Astronomy

  • Length scales (Part I)

    10-10 m 10-5 m 105 m 1010 m 1 m

    Earth-Moon distance 4x108 m (courtesy NASA)

    Michigan width 2x105 m (courtesy Google)

    Red blood cell 1x10-5 m (courtesy PBS)

    Magnetic nanoparticle 5x10-9 m

    Person 2m

  • Length scales (Part II)

    10-3 m

    10-9 m

    10-7 m

    10-5 m

    10-1 m

    10-3 m=1 mm

    10-6 m=1 m=1 (micron)

    10-9 m=1 nm (nanometer)

    Courtesy CSU Hayward

    Head of a pin 1,000,000 nm

    Thickness of a human hair: 100,000 nm

    Courtesy Intel

    Transistors 65 nm

    Visible light 400 to 700 nm

    Distance between atoms in a solid ~0.3 nm

  • Q: What is Nanotechnology?

  • Q: What is Nanotechnology?

    A: Depends on who you ask.

  • Q: What is Nanotechnology? Narrow Nanotechnology is the engineering of functional systems at the molecular scale -Center for Responsible Nanotechnology

    Broad Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nm. -National Nanotechnology Initiative

    We will follow the broad definition for nanotechnology, since we need to understand the properties of small objects before we can build machines from them.

  • 10-3 m

    10-9 m

    10-7 m

    10-5 m

    10-1 m

    Optical microscopy

    Electron microscopy

    Nanotechnology

    How can we see things on the nanoscale?

    The development of scanning probe techniques (STM, AFM) in 1981 revolutionized the imaging of nanoscale systems.

  • Scanning Electron Microscope

    Sandia National Laboratory

    Mite on a chip Attogram (10-18 g) scale

    Courtesy H. Craighead, Cornell University

    Uses reflected electrons to image small objects.

  • Transmission Electron Microscope

    5 nm

    -Fe2O3 nanoparticles

    TEM Philips CM10

    Liver Cell University of New England

    Uses electrons passing through sample to image small objects

  • Scanning Tunneling Microscope

    Courtesy Kiel University

    Courtesy J.C.S. Davis, Cornell

    STM Tip

    Quantum Corral

    Courtesy IBM

    BiO planes in BSCCO

  • Atomic Force Microscope

    Pictures courtesy P. Hoffmann, WSU

    Silicon atoms

    4 nm

    AFM tip

    Images small objects by the mechanical response of a cantilever.

  • What can nanotechnology do for us?

    Biomedical New drug delivery systems. New imaging techniques. Better sunscreens.

    Materials Science Stronger and lighter materials. Combining properties on the nanoscale. Stain resistant pants and better paints.

    Computers Ultra-high density hard drives. Smaller transistors. New polishing methods using nanoparticle slurries.

    Magnetic nanoparticle

  • Why do we need nanotechnology for these things?

    1. Cells are a few microns in size, so nanometer sized objects can freely move through cell walls, into the cell nucleus.

    2. Nanoparticles have a very large surface area, making them useful for applications relying on the interface between different materials.

    3. Electronic components are already less than 100 nm; increasing their performance will rely on working at smaller length scales.

    4. The physical properties of materials at small length scales is very different than in bulk.

  • How do you make nanotechnology?

  • 30 nm lines 90 nm lines Courtesy IBM research

    Lithography

    Top-down approach Like making a statue of an elephant: start with a big block of marble, and chip away everything that doesnt look like an elephant.

    Focused ion beam

    Courtesy C. Kruse, Bremen

  • Expose resist to light using mask.

    Chemically etch regions not protected by the resist.

    Mask Resist Material

    Remove portions of resist not exposed to light.

  • Bottom-up approach Like making a statue of an elephant from Lego, if the Lego blocks were 1 nm across.

    DNA

    Courtesy NIH

    Xenon atoms positioned using STM

    Courtesy D. Eigler IBM

  • DNA Tweezers

    Courtesy B. Yurke, Bell Labs Courtesy C. Mirkin, Northwestern

    Gold-polymer nanorods

    (Self-assembly)

  • How do things change on the nanoscale?

  • Mechanical properties change Silicon spur being broken

    Courtesy J. Parpia, Cornell University

  • Courtesy UC Berkeley

    Carbon nanotubes

    Courtesy D. Ralph, Cornell University

    Single electron transistor

    Electronic properties change

  • Optical properties change

    Courtesy Iowa State

    CdSe Quantum (or Nano) Dots

    Courtesy NYTimes

    Medieval Stained Glass

  • Magnetic properties change

    Courtesy Dataclinic.co.uk

    20 nm

    Iron oxide nanoparticles

    The magnetization direction of magnetic nanoparticles can change spontaneously at room temperature. This is bad for long-term magnetic storage.

    Hard disk data sector

  • Dynamical properties change

    Courtesy P. Keyes, WSU

    Pollen grains in water

    Courtesy P. Keyes, WSU

    Simulation of Brownian Motion

    At small length scales, even individual collisions with water or air molecules can be important.

  • At R=1 mm, A/V=3x103 m-1 At R=10 nm, A/V=3x108 m-1

    Why does surface area matter for nanotechnology?

    Factor of 105 difference!

  • Air resistance

    The relative importance of drag forces increase as the surface to volume ratio, which becomes very large in nanoscale systems.

    alt.

    v

  • % of Au atoms near surface Gold atoms are about 0.2 nm apart. What fraction of Au atoms are near the surface (2 layers away) in a 2 mm dia. gold ball? 20 nm dia. gold ball?

    at R=1 mm, 1.2x10-4 % of atoms are near the surface.

    at R=10 nm, 12 % of atoms are near the surface.

  • Surface loss mechanisms

    Dissipative losses in small devices can be strongly affected by the motion of atoms and molecules bonded to the surface.

    Courtesy H. Craighead, Cornell University

    Cantilever The dissipation in nanodevices can be reduced by over a factor of 10 by heating them to 1000 oC.

    This is important for removing molecules attached to the surface.

  • Nanoscale friction

    Laws of Friction 1. The force of friction is directly proportional to the applied load. 2. The force of friction is independent of the apparent area of contact. 3. Kinetic friction is independent of the sliding velocity.

    NB: Both of these have the same apparent area of contact, but the real area of contact is larger in the bottom case (under a larger normal load).

  • 200 um

    Trailing clamp Leading clamp

    Displacement gauge

    Actuation Plate

    Suspension spring

    Courtesy A. Corwin, Sandia Labs

    Inchworm actuator

    A. Corwin et al, APL 84, 2451 (2004)

    Interfacial adhesion changes frictional forces

  • Atomic scale friction

    A. Socoliuc et al., Science 313, 207 (2006)

    Commensurate surfaces higher friction

    Incommensurate surfaces lower friction

    Atomic scale friction

  • Summary

    Recent scientific developments have spurred nanotechnology research.

    Things on small length scales often act very differently from things at larger length scales.

    This can be used to develop new applications for nanotechnology, but also leads to new types of problems to be addressed.

  • End

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