Self-sealing SiO2 pores on silicon formed by oxidation of microporous silicon

Self-sealing silicon pores with size of 140–160 nm are formed by electrochemical etching. The microporous silicon (MPS) covers the openings and side walls of straight silicon pores (SSPs). The self-sealing SiO2 pores with diameters of 195–205 nm are fabricated from the self-sealing SSPs in an aqueous alkaline medium containing magnesium via oxidation of MPS. The thicknesses of the surface layers covering the SSPs and SiO2 pores are 200 nm and 140 nm, respectively, and the depth of the pores is more than 60 μm. The SiO2 making up the sub-micron pores has a nanoporous structure which allows water and hydrogen molecules to pass through in an aqueous solution.

Graphical abstractMicroporous silicon (MPS) is oxide to silicon oxide. Straight silicon pore (SSP) is changed to SiO2 poreFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The self-sealing sub-micron pores of SiO2 are fabricated from the self-sealing straight silicon pores (SSPs). ► The SiO2 making up of the pore shows a porous structure. ► The aqueous alkaline medium containing magnesium is used to oxidize microporous silicon to porous SiO2. ► The maximum depths of SSPs and SiO2 pores are more than 60 μm.