Abstract
Porous silicon (PSi) exhibiting dual optical properties, both Fabry-Pérot fringe and photolumincence, was developed and used as chemical sensors. PSi samples were prepared by an electrochemical etch of p-type silicon under the illumination of 300-W tungsten lamp during the etch process. The surface of PSi was characterized by cold field-emission scanning electron microscope. PSi samples exhibited a strong visible orange photoluminescence at 610 nm with an excitation wavelength of 460 nm as well as Fabry-Pérot fringe with a tungsten light source. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organophosphate vapors. An increase of optical thickness and quenching photoluminescences under the exposure of various organophosphate vapors were observed.
Highlights
Since the discovery of visible photoluminescence from nanocrystalline porous silicon (PSi) [1], PSi has been intensively investigated for a variety of applications such as chemical [2] and biological sensors [3] and drug delivery system [4], especially that PSi is an ideal candidate for gas- or liquid-sensing applications since it has a very large specific surface area on the order of few hundreds of square meters per cubic centimeter
An anodic etch of p-type silicon wafer with resistivities of 1 to approximately 10 Ωcm in ethanolic HF solution generally produces PSi single layer with a network of microporous rather than mesoporous or macroporous and exhibits Fabry-Pérot fringe pattern in the optical reflectivity spectrum
TEP with Cu(II) complex better the discrimination. These results demonstrated the potentiality of PSi sensors for the detection of nerve agent simulant
Summary
Since the discovery of visible photoluminescence from nanocrystalline porous silicon (PSi) [1], PSi has been intensively investigated for a variety of applications such as chemical [2] and biological sensors [3] and drug delivery system [4], especially that PSi is an ideal candidate for gas- or liquid-sensing applications since it has a very large specific surface area on the order of few hundreds of square meters per cubic centimeter. PSi prepared from p-type silicon wafer under dark condition exhibits well-defined Fabry-Pérot fringes in the optical reflectivity spectrum. Condensation of organic vapors in the pores can lead to a shift in the Fabry-Pérot fringes by modification of the refractive index of PSi films [9]. This property has been exploited to develop PSi sensors for the detection of toxic gases [10,11], solvents [12], DNA [13], and proteins [3,14,15]. Organic vapors have been detected quantitatively by quenching of photoluminescence of the quantumconfined Si crystallites in PSi [16].
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