LOCAL FIELD-EFFECT IN SMALL SEMICONDUCTOR CLUSTERS AND PARTICLES

When small semiconductor clusters and particles are embedded in a dielectric medium with a lower refractive index (such as glasses, polymers, organic liquids, and air), the local electric field near the particle surface can be greatly enhanced compared to the incident field upon illumination. This local field enhancement effect can be important in the study of the spectroscopy and photophysical processes of semiconductor clusters and particles. Here we first present computational results on the size and wavelength dependence of the local field intensity enhancement factors for CdS and TiO2 particles, two commonly used photocatalysts. We then report an experimental attempt to observe this local field effect, manifested as structural resonances in the photoluminescence spectrum of monodisperse 1.1-mu-m CdS particles.