DFWM study of thin films containing surface-modified CdS nanoparticles

Degenerate four-wave mixing (DFWM) was used as a technique to estimate the third-order optical susceptibility, chi((3)) (-omega; omega, -omega, omega) , of thin films prepared from cadmium sulfide (Cds) colloidal solutions. Th e formation of CdS films on a substrate, without any change in the particle size, enhanced the quantum yield of an excitonic band by removing a large number of surface traps. This film showed a large chi((3)) value near simil ar to 10(-7) esu around the exciton resonance at room temperature. This was possibly brought about by an effective surface passivation as well as a hi gh CdS microcrystallite concentration.