Porous silicon (PS) exhibits various morphological features depending on experimental conditions such as doping of the bulk material, electrolyte concentration, etching volume, and temperature. Due to the characteristics and features, the applications range from capacitors, micro-system technologies, electrode materials, solar cells, fuel cells, to membranes. PS is usually produced by the application of low anodic bias on the silicon substrate immersed in a hydrofluoric acid solution. PS is also formed in organic electrolytes containing hydrofluoric acid while water, originated from hydrofluoric acid (49% HF), is usually included in the electrolyte. It is important to note that the formation of PS from low-medium doped n-type silicon is favorably performed under illumination, since n-silicon under anodic polarization is in depletion.
A novel RTIL, EtMeIm(FH)nF, with high conductivity (100 mS cm-1 at 298 K) was recently reported . The (FH)nF- based RTIL is considered as acidic and moisture-stable. This RTIL has been also investigated as a medium for fluorination, and as an electrolyte for fuel cells. In the present study, EtMeIm(FH)2.3F was selected as an electrolyte since at this specific n value it is vacuum stable and highly conductive at room temperature. We report that a formation of a macro-PS is feasible by applying positive potential on n-type silicon in a non-aqueous EtMeIm(FH)2.3F under no illumination. The effects of time and potential on PS formation and structure are discussed.
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