Deposition of a rare earth salt layer on a silicon substrate with subsequent spark processing yields a porous Si layer and SiO_2 cap doped wiht the rare earth ion. We have characterized luminescent Er-doped porous SiO_2 on Si by scanning electron microscopy, energy dispersive X-ray spectroscopy, as well as visible and near IR photoluminescence (PL) spectroscopies. energy-dispersive x-ray maps indicate that the erbium concentration in the porous layer can be controlled by varying the molarity of the erbium concentration in the porous layer can be controlled by varying the molarity of the erbium solution deposited on the substrate prior to spark processing. Visible PL measurements reveal that the concentration of Er~3+ is proportional to the resultant intensity of the visible fluorescence transitions; however, for the near IR fluorescence peak at 1.54 um m, self-quenching due to erbium clustering occurs at higher concentrations. Erbium-doped porous silicon layers can also be obtained by diffusion of an erbium salt into porous silicon formed by anodic etching of Si in hydrofluoric acid. Densification of the porous Si layers through high temperature oxidation after erbium diffusion forms erbium-doped SiO_2 layers.
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