HIGH REFRACTIVE-INDEX FILMS OF POLYMER NANOCOMPOSITES

Solutions of PbS particles and gelatin were used for the preparation o f nanocomposites by a spin-coating process. This allows for the prepar ation of nanocomposite films with controlled thickness, e.g., between 40 nm and 2 mum for a film containing 45 wt. % PbS. Surface roughness and film thickness were investigated by surface profilometry and scann ing electron microscopy (SEM). The refractive index at 632.8 nm can be expressed by a linear function of the volume fraction of PbS in the r ange of 0 to 55 vol. % PbS. In this range, the refractive index increa ses from 1.5 to 2.5 with increasing PbS ratio and belongs, therefore, to the highest refractive indices known for polymeric composite materi als.