Surface treatment effect of ion irradiation on size-quantized semiconductor particles incorporated into LB films

The surface of semiconductor particles are often full of defects, which hampers their practical applications. Chemical treatment has so far proven to be effective in overcoming such limitations, In this study, we use ion irradiation instead of chemical treatment and show that ion irradiation provides good surface passivation of semiconductor particles. Size-quantized CdS fine particles with different sizes were successfully incorporated into Langmuir-Blodgett (LB) films and then irradiated with 1 MeV H+ beams. Changes in the electronic states of the particles were examined by in-situ observation of the steady-state spectra and time-resolved profiles of the high-energy, ion-induced emissions. The high-energy ion irradiation was found to significantly decrease the density of the carrier-trapping midgap states which mainly exists in the surface region, and leads to an order of increase in the quantum efficiency of the band-edge emission or the emission via very shallow traps. This clearly shows that the ion irradiation provides good surface passivation.