Surface skin development and rupture during sol-gel spin-coating

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Spin coating is one of the standard methods for depositing sol-gel, nanocomposite, or polymer coatings onto flat substrates (silicon wafers, glass plates for displays, sensor substrates, etc.). Our recent research has been focused at understanding a wide variety of defect formation mechanisms and looking for ways to prevent these defects. A key aspect of spin-coating is the solvent evaporation that happens at the top surface of the coating fluid during spinning - even while the fluid is moving rapidly, radially, outward on the substrate. As the fluid gets physically thinner, concentration gradients can develop within the fluid as a result of the evaporation. The enrichment of the precursors at the top surface can cause premature gelation there, in other words a "skin" may form. This skin layer is also more resistant to stretching than the underlying fluid and can retard radial fluid motions as well as further solvent evaporation. It is even possible for the stretching forces to be large enough that fracture or tearing of the skin occurs. These surface ruptures create wispy locations of significantly thinner coating or small randomly located linear rips, but they do not typically result in complete penetration through the coating. The occurrence of these defects depends to a large degree on the volatility of key solvents used in the sol-gel process, with less volatile solvents being less likely to result in surface ruptures.

Original languageEnglish
Pages (from-to)225-228
Number of pages4
JournalJournal of Sol-Gel Science and Technology
Volume31
Issue number1-3 SPEC.ISS.
DOIs
Publication statusPublished - Aug 2004

Fingerprint

Spin coating
Sol-gels
coating
Skin
gels
Fluids
fluids
coatings
Coatings
Evaporation
evaporation
Defects
Stretching
defects
Substrates
tearing
volatility
gelation
Gelation
sol-gel processes

Keywords

  • Defects
  • Fluid flow
  • Spin-coating
  • Surface skin

ASJC Scopus subject areas

  • Ceramics and Composites

Cite this

Surface skin development and rupture during sol-gel spin-coating. / Birnie, Dunbar P.

In: Journal of Sol-Gel Science and Technology, Vol. 31, No. 1-3 SPEC.ISS., 08.2004, p. 225-228.

Research output: Contribution to journalArticle

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