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Diamond-hexagonal Semiconductor Nanocones with Controllable Apex Angle

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PIs: L. Cao, L. Laim, B. Nabet & J. E. Spanier (Drexel University); C. Ni (University of Delaware)

Conical or tapered nanostructures are important in a number of diverse application areas, including field emission, scanning probes, manipulators, and nanoscale syringes. Many applications such as these require nanostructures with precise control of apex angles. The synthesis of semiconductor nanocones (SNCs) with controlled apex angles enables investigation of shape-related properties and also permits study of diameter-dependent properties within individual nanostructures. The detailed characterization of SNCs is expected to provide new insights into their growth and unique properties.

These results required all of the following:

  • Vapor-liquid-solid growth of metal-catalyzed semiconductor nanostructures (silicon and germanium nanocones, SiNC, GeNCs)
  • Characterization of the SiNCs and GeNCs using high-resolution transmission electron microscopy and Raman scattering spectroscopy
  • Crystallographic and group theoretical analysis and modeling for the interpretation TEM and Raman spectroscopy.

Conclusions:

Si and Ge nanocones were produced with selectable control of average apex angle with narrow dispersions.

SiNCs growth based on a competition between catalyzed (axial) and homogeneous decomposition (radial) growth.

SiNCs and GeNCs possess the diamond-hexagonal polymorph, an ambient-pressure metastable phase which possesses unusual electronic structure properties which are relevant to photonics.

References: Cao, Laim, Ni, Nabet and Spanier, JACS Communications 127, 18782 (2005).

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