Early dewetting stages of thin polymer films initiated by nanoindentation

Ioannis Karapanagiotis, William W Gerberich, D. Fennell Evans

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

We study the effect of nanoindentation induced defects on thin (h = 50 nm) and thick (h = 100 nm) polystyrene (PS) films, spin cast on nonwettable silicon (Si) substrates. Indents with depths of penetration higher than the film thicknesses were imposed. Upon heating above the bulk glass transition temperature (Tg) of PS, some of the indents healed, resulting in a flat polymer surface, and some grew laterally and dewetted the substrate. Our goal is to establish a criterion that can predict the final result (healing or growing) of the indent evolution. We find that the applied force during the nanoindentation and the substrate area exposed to the air after the imposition of an indent can only be used as crude rules, since they do not provide a "cutoff" border, that distinguishes the growing from the healing indents. On the contrary the excess surface energy (ΔFγ) of the system, that is added to the initially flat coating with the formation of an indent, provides a clear critical value, ΔFγ,crit, which separates the growing from the healing indents. An indent grows when ΔFγ > ΔFγ,crit, and it heals when ΔFγ < ΔFγ,crit.

Original languageEnglish (US)
Pages (from-to)2375-2379
Number of pages5
JournalLangmuir
Volume17
Issue number8
DOIs
StatePublished - Apr 17 2001

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    Karapanagiotis, I., Gerberich, W. W., & Evans, D. F. (2001). Early dewetting stages of thin polymer films initiated by nanoindentation. Langmuir, 17(8), 2375-2379. https://doi.org/10.1021/la001076b