Fabrication of Nanostructures

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Fabrication of Nanostructures

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Fabrication of Nanostructures

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

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