This study reveals the influence of the surface energy and solid/liquid
boundary condition on the breakup mechanism of dewetting ultra-thin polymer
films. Using silane self-assembled monolayers, SiO2 substrates are rendered
hydrophobic and provide a strong slip rather than a no-slip solid/liquid
boundary condition. On undergoing these changes, the thin-film breakup
morphology changes dramatically -- from a spinodal mechanism to a breakup which
is governed by nucleation and growth. The experiments reveal a dependence of
the hole density on film thickness and temperature. The combination of lowered
surface energy and hydrodynamic slip brings the studied system closer to the
conditions encountered in bursting unsupported films. As for unsupported
polymer films, a critical nucleus size is inferred from a free energy model.
This critical nucleus size is supported by the film breakup observed in the
experiments using high speed \emph{in situ} atomic force microscopy.Comment: 8 pages, 9 figures, including supplementary materia