Fabrication and optical characterization of multi-encoded rugate porous silicon/polymer composite.

Multi-encoded rugate porous silicon (MRPS)/polystyrene composite films were fabricated by using a free-standing multi-encoded rugate PS and polystyrene. MRPS exhibiting three reflection resonances was generated by an electrochemical etching of silicon wafer using a composite waveform summed three computer-generated pseudo-sinusoidal current waveforms, which were corresponded to the each of the sine components varied from 0.40, 0.38, to 0.36 Hz, with a spacing of 0.02 Hz between each sine component. They displayed three sharp photonic reflection resonances in the optical reflectivity spectrum. MRPS/polymer composite films obtained by casting of polystyrene polymer solution exhibited excellent photonic characteristics and robust structure upon flexing. For a possible application as VOCs sensor, these films were served for the detection of organic vapors such hexane and methanol.