Self-trapped exciton state in Si nanocrystals revealed by induced absorption

Abstract

We report results of time-resolved induced absorption (IA) spectroscopy on Si nanocrystals (Si NCs) embedded in a SiO${}_{2}$ matrix. In line with theoretical modeling, the IA amplitude decreases with probing photon energy, however only until a certain threshold value. For larger photon energies, an increase of IA is observed. This unexpected behavior is interpreted in terms of the self-trapped exciton state whose formation in Si NCs was put forward some time ago based on theoretical considerations. Here, we present a direct experimental confirmation of this supposition.