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A NF3/UV photo-chemical surface treatment of porous silicon is presented. The UV photons are provided by an excimer lamp. This treatment strongly enhances the photoluminescence of porous silicon. The increase of PL intensity is about 1-2 orders of magnitude at treatment temperatures in the range of 300-400°C. Using AFM and Auger measurements, it is found that the PL enhancement can be correlated with the growth of about micron thick SiOx layer with the x value close to 2, and incorporation of fluorine. The overall effect of photoluminescence enhancement is suggested to be due to the NF3/UV photothermal etching of the as-formed native oxide, as well as to the cleaning and passivation of the porous silicon surface with fluorine, followed by a rapid growth of a more stoichiometric oxide SiOx(x≈2) layer in air.

Direct integration of sol-gel derived ceramic films with porous silicon, without buffer layers, has been demonstrated. The effects of ceramic type, solvent type, solution concentration, as well as, porous silicon layer thickness, porosity and preparation conditions, on the quality and microstructure of sol-gel films/porous silicon integrated systems have been studied. The following ceramic compositions have been applied to porous silicon as protective coatings: PZT (PbZr0.3Ti0.7O3), PLZT (Pb0.925La0.055Zr0.3Ti0.7O3), ZrO2, TiO2, with 2-methoxyethanol and 2-ethoxyethanol solvents, 0.5 and 0.1 M precursor solution concentrations. The LSCO (La0.5Sr0.5CO.3) water based sol-gels have been deposited for electroconductive purposes.The best compositions for integration, giving transparent, mirror-like, uniform ceramic films with fine morphology and strong adhesion, were found to be the TiO2 and ZrO2 as well as, the diluted (0.1 M) PZT (PbZr0.3Ti0.7O3) sol-gel precursors. Conductive LSCO sol-gel derived films showed improved wetting and stronger adhesive interaction with porous silicon, as compared to polished silicon wafers.

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