Semiconductors

As far as semiconductors are concerned, it is likely that a crystal phase transition depending on nanoparticle size can occur in certain cases. However, the systems investigated as yet have not produced conclusive results. The case of CdS nanoparticles is worth mentioning in this context. These are obtained with a wurtzite-type structure (as in the bulk solid) for diameters greater than 5 nm, whereas for very small sizes (3 nm), a zinc blende structure is observed. However, the latter is apparently metastable and seems to be obtained for purely kinetic reasons during formation. Grain size dependent crystalline phase transitions exist for a wide range of materials. This is therefore an intrinsic property of nanomaterials.