Photoluminescence of Er-doped silicon nanoparticles from sputtered SiOx thin films

We present a study of the Er3+ photoluminescence from Er-doped thin SiOx films prepared by reactive RF sputtering from a silicon target partially covered by metallic erbium platelets in an Ar + O2 atmosphere. Annealing at 1250 °C induces the formation of silicon nanocrystals and modifies the Er3+ luminescence spectrum due to changes in the Er3+ environment. The photoluminescence efficiency decreases by two orders of magnitude with nanoparticle formation. This decrease may be due to less efficient energy transfer processes from the nanocrystals than from the amorphous matrix, to the formation of more centro-symmetric Er3+ sites at the nanocrystal surfaces or to very different optimal erbium concentrations between amorphous and crystallized samples.