The effect of size and depth profile of Si-nc imbedded in a SiO2 layer on the photoluminescence spectra

It has been demonstrated that the size and depth profile of silicon nanocrystals produced by implanting Si+ ions (∼100 keV) into SiO2 are dependent on the implantation dose. Here, we demonstrate that these parameters have, in turn, a significant effect on the photoluminescence (PL) spectra of Si-nc imbedded in a thin SiO2 layer formed on a silicon backing. Strong spectral modulation is observed compared with the PL spectra of Si-nc imbedded in bulk SiO2 for implantation doses of 6×1016, 8×1016 and 1×1017 Si+/cm2, whereas for an implantation dose of 3×1017 Si+/cm2, very little spectral deformation is noted. The modulation in the luminescence spectrum is caused by optical interference effects produced by the layered structure. Two types of optical interference must be considered: the pump laser standing wave, which determines the pump amplitude as a function of depth in the SiO2 layer, and the optical interference of the Si-nc luminescence, which is a function of the depth of the Si-nc in the SiO2 layer. Such modulation in a layered structure can serve to tailor the Si-nc luminescence spectrum for specific applications.