Atypical electron confinement in semiconductor nano-platelets
With this in mind, researchers from IEMN in collaboration with a team from the University of Ghent have shown that it is possible to obtain, by colloidal chemical synthesis processes, anisotropic CdSe nanoparticles, called NanoPlanets (NPLs), for which the electron confinement can be finely tuned in all 3 spatial directions. These NPLs exhibit strong quantum confinement depending on their thickness which is in the nanometer range and is controlled to the nearest atomic layer. The lateral dimensions can be varied from a few nanometers to a hundred nanometers which allows to modify the electron confinement and to study finite size effects. Tunneling microscopy studies have shown that, for NPLs with finite lateral dimensions smaller than 30 nm, the densities of electronic states show Van Hove singularities, characteristic of 1D materials, in very good quantitative agreement with theoretical calculations of strong bonds, and in clear contradiction with the paradigm widely accepted for a decade for NPLs, of a 2D density of state for electrons in the conduction band.
These first results published in Nanoletters1 pave the way towards an understanding of the electronic properties at the dimensional boundary, which is essential for the development of functional hetero-nanostructures that would use the inherent advantages of different dimensionalities to optimize performance.