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Electrochemically Formed Porous Silica

Physique de la Matière Condensée, Ecole Polytechnique, CNRS, 91128 Palaiseau, France
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Materials 2011, 4(5), 825-844; https://doi.org/10.3390/ma4050825
Received: 7 March 2011 / Revised: 6 April 2011 / Accepted: 20 April 2011 / Published: 26 April 2011
(This article belongs to the Special Issue Porous Materials 2011)
Controlled electrochemical formation of porous silica can be realized in dilute aqueous, neutral-pH, fluoride medium. Formation of a porous film is initiated by sweeping the potential applied to silicon to values higher than 20 V. Film formation, reaching a steady state, may be pursued in a wide range of potentials, including lower potentials. The origin of a threshold potential for porous film initiation has been explained quantitatively. All of the films appear mesoporous. Films grown at high potentials exhibit a variety of macrostructures superimposed on the mesoporosity. These macrostructures result from selective dissolution of silica induced by local pH lowering due to oxygen evolution. Films grown at potentials lower than 15 V appear uniform on the micrometer scale. However, all of the films also exhibit a stratified structure on the scale of a few tens of nanometres. This periodic structure can be traced back to the oscillatory behavior observed during the electrochemical dissolution of silicon in fluoride medium. It suggests that periodic breaking of the growing film may be responsible for this morphology. View Full-Text
Keywords: silicon; anodic oxide; electrochemical dissolution; morphologies silicon; anodic oxide; electrochemical dissolution; morphologies
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Chazalviel, J.-N.; Ozanam, F. Electrochemically Formed Porous Silica. Materials 2011, 4, 825-844.

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