Luminescence Efficiency of Si/SiO2 Nanoparticles Produced by Laser Ablation

Abstract

Photoluminescence properties of Si(core)/SiO 2 (shell) nanoparticles produced by pulsed laser ablation in aqueous solution are investigated with the purpose to highlight the microscopic processes that govern the emission brightness and stability. Time resolved spectra evidence that these systems emit a µs decaying band centered around 1.95 eV, that is associated with the radiative recombination of quantum-confined excitons generated in the Si nanocrystalline core. Both the quantum efficiency and the stability of this emission are strongly dependent on the pH level of the solution, that is changed after the laser ablation is performed. They enhance in acid environment because of the H + passivation of non radiative defects, located in the Si/SiO 2 interface, which causes the growth of IR-active SiH groups. On the basis of the reported experimental results and previous literature data, we propose that the non radiative defects are located in the suboxide interlayer between Si and SiO 2 and their nature is affected by the latter.