Fabrication of Nanostructures
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Fabrication of Nanostructures

Fabrication of Nanostructures

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Fabrication of Nanostructures Presentation Transcript

  • 1. Fabrication of Nanostructures
  • 2. Two Fundamental Approaches
    • Top Down
    • 3. Removing material from a larger structure of make smaller ones.
    • 4. Etching
    • 5. This is the one we will be talking about.
    • 6. Bottom Up
    • 7. Adding material to already small structures to create larger ones.
    • 8. Molecular Chemistry
  • Top down Techniques for Making Nanostructures
    • E-Beam Lithography.
    • 9. Scanning Tunneling Microscopy.
    • 10. Self Assembly.
  • E-beam Lithography
    • Minimum features 4nm.
    • 11. Typical features 20-50nm. As a result of back scattering of electrons.
    • 12. Uses and high energy electron beam to break or add bonds to the photoresist.
  • E-beam Lithography Photo resists
    • The high energy electron beam breaks the bonds of positive photoresist.
    • 13. The electron beam creates bonds in negative photoresist.
    • 14. The most common e-beam photoresist is polymethylmethacrylate (PMMA).
  • E-beam Examples
    • Single Electron Transistor
    • 15. Currents consist of individual electrons
  • Fabrication with STM
    • Minimum features: atomic manipulation
    • 16. Maximum features: couple nanometers.
  • Operation of STM
    • Electrons in the STM tip are able to tunnel through the small gap between the tip and the sample.
    • 17. The tip is scanned across the sample.
    • 18. The STM controller maintains a constant current and adjust the vertical position to do so.
    • 19. The vertical position is measured, and is a direct representation of the surface of the material.
  • STM Example
  • 20. Fabrication of Quantum-Dots using STM
  • 21. Self Assembly
    • A very thin layer of material is deposited onto a substrate of other material.
    • 22. Stresses occur as a result of the mismatch of crystal lattices between two different materials.
    • 23. The thin material tends to clump up forming quantum dots.
  • Example of Self Assembled Quantum-Dots