Contact Angle Studies on Porous Silicon: Evidence for Heterogeneous Wetting and Implications of Oxidation

A study of wetting was carried out on porous silicon films with pore diameters spanning three orders of magnitude. Water contact angle measurements on adjoining porous and nonporous regions yielded Wenzel roughness ratios that were either unphysical (less than unity) or unrealistically low when comp...

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Bibliographic Details
Published in:SILICON 2023-08, Vol.15 (13), p.5703-5710
Main Authors: Spencer, Stephen J., Deacon, Christopher G., Andrews, G. Todd
Format: Article
Language:English
Subjects:
Chemistry
Chemistry and Materials Science
Contact angle
Diameters
Environmental Chemistry
Inorganic Chemistry
Lasers
Materials Science
Optical Devices
Optics
Original Paper
Oxidation
Photonics
Polymer Sciences
Porosity
Porous silicon
Silicon films
Wetting
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Summary:A study of wetting was carried out on porous silicon films with pore diameters spanning three orders of magnitude. Water contact angle measurements on adjoining porous and nonporous regions yielded Wenzel roughness ratios that were either unphysical (less than unity) or unrealistically low when compared to those expected from specific surface area considerations. Moreover, results obtained from a sample consisting of a microporous film on a macroporous layer gave contact angles that were very similar to those found on films consisting of only a single microporous layer, contrary to what would be expected for complete filling of the pores by liquid. Values for wetted surface fractions calculated from the Cassie-Baxter model are unreasonably high for micro- , meso- and oxidized macroporous films considering their porosities, while relatively oxide-free macroporous films give wetted surface fractions in accord with those expected based on film porosity. Collectively, these results show that the predominant mode of wetting on these films is heterogeneous.
ISSN:1876-990X
1876-9918
DOI:10.1007/s12633-023-02384-9