Organization of Nanowire Arrays for Integrated Nanosystems

1

• Organization of Nanowire Arrays for Integrated
  Nanosystems
• Presenter Octavian Florescu
• Authors Lieber group
• Department of Chemistry and Chemical Biology,
• Harvard University

2
Outline

• Organization of nanowires
• Why is it important?
• Criteria for organization
• Methodology
• Results
• Conclusions

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Organizing Nanowires

• Why?
• Critical to the realization of integrated
  electronics, photonics and sensors
• Criteria for organization
• Controllability
• Yield
• Reproducibility
• Reliability
• Cost

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Controlled Growth of Nanowires

• p or n-SiNW with good diameter distribution were
  grown by VLS

• Substrate was oxidized silicon
• Catalyst was Au nanoparticls
• Reactant was silane

Cui et al., APPL. PHYS. LETT VOL. 78, NO 15
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Deposition of Nanowire Arrays on Substrate

• a) SiNW are suspended using a surfactant in
  nonpolar solvent.
• Compressed in a Langmuir-Blodgett trough.
  Compression determines center to center spacing.
• b) SiNW transferred onto Si substrate.

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
1255-1259
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Deposition Results

• 200nm to 2um pitch realizable
• Decent control of the periodicity and wire width
• Can cover over 20cm2 in area.

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
1255-1259
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Finer Deposition

• In this scenario SiNW are coated with a
  sacrificial layer and are compressed until they
  touch.
• Can be used as a mask for deposition of metal NW.

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
951-954
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Finer Deposition Results

• 90nm pitch was produced with 40nm linewidth
• Control of both pitch and linewidth
• In this case pitch independent of LB compression

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
951-954
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Integration with Electronics

• a) Electrodes with same pitch as SiNW align well
  with the nanowires
• b) PL used to pattern active areas containing
  SiNW
• Electrodes deposited over SiNW active areas

Jin et al., NANO LETTERS, 2004, Vol. 4, No.
5 915-919
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Realization

• 80 of the 3000 electrodes are bridged by SiNWs
• Can be combined with NIL, EUV to generate very
  dense arrays of electrodes

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
951-954
11
Electrical Performance

• gm 1250nA/V
• Ion/Ioff 107
• Ssubthreshold 160mV/decade
• µ 307cm2/Vs

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
951-954
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Another Realization

• Size of FET depends on the spacing between SiNWs,
  which depends on the LB compression.
• Decent control of VTH

Whang et al., NANO LETTERS 2003, Vol. 3, No. 9,
951-954
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Conclusions

• Good
• 80 device yield
• Inexpensive
• Reproducible (?)
• Bad
• Low gain
• Unknown
• Controllability of device characteristics
• Reliability
• Not suitable yet for ICs but can be interesting
  for use in thin film electronics and as
  transducers.

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Thank you!