Nanosized semiconductors in glasses prepared by the sol gel method: their optical properties and potential uses

摘要

Semiconductor nanocrystals (NCs) in transparent media have, especially in sol gel glasses, received recently a large attention due to their promising applications in non-linear optics and optical switches. Those nanometer-sized crystals, which are comparable with the bulk exciton Bohr radius, exhibit an intermediate behavior between a bulk crystal and an isolated molecule. For example, CdS and CdSe NCs and CdTe exhibit a large optical non-linearity. Lead sulfide (PbS) is suitable for the telecommunication application, because its bulk band gap is located at 0.41eV at 300K. The latter is blue shifted to the spectral regime of 0.7-1.5μm (1.77-0.82 eV) upon the decrease of the PbS NCs diameter below the size of the exitonic Bohr radius (16nm), due to a quantum confinement effect.