Surface and Quantum Effects in Nanosized Semiconductor

Abstract

Novel properties of nano-scale semiconductors based on the surface and quantum effects have been studied and applications identified. Spherical potential well model is used to study quantum effect whereas basic geometrical models are used for the surface effect. We have shown such effects to be the fundamental factors responsible for the novel nanosized semiconductor characteristics different from the bulk of same material. It is found that the surface area to volume ratio follows inverse power law. Thus at nanoscale, the surface to volume ratio increases significantly to enhance chemical reactivity. In addition, the increased surface area makes most nananocrystals highly soluble in liquid and dramatically lowers their melting temperature. The result strongly suggests also that the shape of the nanoparticles influences the surface area which has huge impact on their properties and performance. Our results of quantum size effect reveal that spatial confinement of charge carriers within semiconductor nanocrystals significantly modulates their properties such as size dependent absorption and emission spectra with non-zero discrete electronic transition energies as well as their blue shift band gaps. Thus by changing the size of the particle, we can literally fine-tune a material property of interest such as optical, electrical, and surface area. Specifically we found that InAs and InSb nano semiconductor optical absorption spectrum, in contrast to their bulk, can be tuned in broad range of UV to IR regions which are favorable operating wavelengths for nano photonic technology such as IR photo detectors and full spectrum solar cells applications.