Study of Erbium Doped Silica Films Containing Silicon Nanograins

SiO_x(1<x<2) film doped with 0.11 at % Er was prepared by electron gun evaporation. Three successive annealing steps at 850, 900 and 1000degC, 1 hour for each step, were performed to achieve a phase separation between Si and SiO₂. The 900degC annealing step did induce the phase separation, observed by the ellipsometry measurement. With respect to the 900degC annealing step, the 1000degC annealing step completed the decomposition, red-shifted the peak energy of the Si-related PL band, and decreased the intensity of the Er PL band. The Er effective excitation cross sections were successfully determined, which were around 1*10^-16 cm². The Er cross section decreased with increasing excitation wavelength, in good agreement with the observation of photoluminescence excitation (PLE) spectra. With more annealing steps, the Er cross section slightly increased. In addition, we have employed an oxidation procedure to obtain an Er doped SiO₂ film. After oxidized, the Si-related PL band disappeared and the Er PL intensity was extremely reduced indicating the Er ions were principally excited by the energy transferred via silicon nano grains.