Self-assembly Nanostructure and Lithography

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Self-assembly Nanostructure andLithography

• Prepared by
• Thu Nguyen

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Self-Assembled Nanostructures

• Self-assembled epitaxical quantum nanostructures
  are a class of nanostructures created by
  exploiting naturally occurring forces between the
  constituents, usually atoms and/or molecules, and
  a crystalline substrate such that the atoms of
  the resulting nanostructure have a definite
  spatial relationship with the underlying
  substrate atoms.
• Since the nanostructures form during a film
  growth process, rather than through post-growth
  patterning and etching on the nanoscale, these
  have been dubbed self-assembled (or
  self-organized) nanostructures.

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The directed self-assembly process can produce
large, virtually perfect arrays of bent lines at
the nanoscale. Such arrays could form the basis
of nanoscale electronic devices.
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Electron-beam Lithography

• The technique in brief consists of scanning a
  beam of electrons across a surface covered with a
  resist film sensitive to electrons, thus
  depositing energy in the desired pattern on the
  resist film.
• Write lines with widths of only a few nanometers
  in a layer of photoresist on a silicon substrate.
• Electron beams do not cause blurring of the
  edges of features because at atomic scale they
  dont diffract.
• Can be done at nano-scale, as compared to
  photolithography, which is done at micro-scale.
• Expensive and impractical for large-scale
  manufacturing because the beam of electrons is
  needed to fabricate each structure, thus the
  process can be done with one line at a time.

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• Applications
• Application areas of e-beam lithography span a
  wide range from cryo-electric devices,
  opto-electronic devices, quantum structures,
  transport mechanism studies of semiconductor/super
  conductor interfaces, microsystem techniques,
  optical devices.
• The use of electron-beam lithography on pentacene
  and poly(3-hexylthiophene) field-effect
  transistor to achieve device isolation and enable
  the realization of nanoscale organic circuits.
• Can be used in the fabrication process by soft
  lithography.

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Soft Lithography

• Soft lithography uses an elastomeric mold to
  shape soft materials.
• This technique has been recently developed as a
  tool for micro- and nano-fabrication
  (optoelectronic components)

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