Size dependence of tetrahedral bond lengths in CdSe nanocrystals

The structural characteristics of organically passivated CdSe nanocrystals (NCs) were investigated with x-ray diffraction and extended x-ray absorption fine structure. As the NC size decreases, the axial bond length R-(1) for an atomic tetrahedron extends but the equatorial bond length R-(2) contracts, with a similar tendency of distortion for the lattice parameters of the wurtzite structure. The authors suggest that the observed hexagonal distortion is attributed to the surface stress of the NCs related to the organic passivation effect and the relaxation of atomic positions at the stacking fault interface. (c) 2007 American Institute of Physics.