Modification of optical properties of oxidised porous silicon by pore filling

We report the experimental study of changes in optical properties of oxidised porous silicon induced by pore filling with salts from aqueous solutions. Our experiments demonstrate that pore filling is a simple and effective method for tuning the refractive index of porous silicon, which can be applied locally. This method can be used for creation of waveguides and other planar optical components. Our results correlate with previously reported works on the subject and provide information, which can be useful for the future investigation of porous materials. Our samples were thin porous layers on top of Si wafers. We used aqueous solutions of several phosphate salts with various concentrations for filling the pores. After the pore filling, the dry samples were examined using optical spectrometry, microscopy (optical and electron) and EDS methods. The paper provides description of the experimental procedures, data analysis and comparison with theoretical calculations.