RESEARCH INTEREST
Nanocrystal / Nanomechanics / Particle Assembly / Coalescence

How Can You Generate Cubic Nanoclusters?
Nanoparticles are considered as building blocks for nanostructures and associated devices. One of the significant challenges in the use of nanoclusters, is the control of cluster shape when grown from the gas–phase. Recently, the Kortshagen group has succeeded in generating cubic Si nanoclusters in non-equilibrium plasma. In this research we consider the energetics of various shaped Si nanoclusters, and the role that hydrogen surface termination plays.

 

TEM images of cubic Si
Evolution of a truncated octahedron shape of Si
  

  • Dynamics suggest that the cube is not the most stable shape.
  • Why cubes in experiments?

 

  
     
Experiments by Kortshagen et al at U of Minnesota    
     

Stability of a Nanoparticle

  
Study of energetics of various cluster shapes also suggests that the truncated octahedron shape is the most stable

HOWEVER...
 

The plasma synthesis contains a lot of hydrogens in the process. We assume that the clusters are coated by hydrogen atoms.

Cube is the most stable shape!
     

 

A decade ago, Sasaki et al studied etching rate of various Si surface directions experimentally.

(100) Si surface has the highest etching rate

Assume etching generates the cubic shape in the process

  

Comparison of etching rate ratio

Experiement:

MD simulation:
    Good Agreement