title: Experimental verification of the formation mechanism for pillar arrays in nanofilms subject to large thermal gradients.
abstract: The free surface of molten nanofilms is known to undergo spontaneous formation of periodic protrusions when exposed to a large transverse thermal gradient. Early time measurements of the array pitch and growth rate in polymer melts confirm a formation process based on a long wavelength thermocapillary instability and not electrostatic attraction or acoustic phonon driven growth as previously believed. We find excellent agreement with theoretical predictions provided the nanofilm out-of-plane thermal conductivity is several times larger than bulk, an enhancement suggestive of polymer chain alignment.
authors.affiliation: California Institute of Technology, 1200 E. California Blvd., T. J. Watson Sr. Laboratories of Applied Physics, MC 128-95, Pasadena, California 91125, USA.
authors.forename: Euan
authors.initials: E
authors.lastname: McLeod
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Troian