Improved Measurements of the Dominant Mode Wavelength in Viscous Nanofilms Undergoing 3D Pillar Growth Via B\'enard Type Instability

Free surface viscous nanofilms exposed to an initial uniform and very large transverse thermal gradient are prone to spontaneous formation and growth of nanopillars typically separated by tens of microns or less. Linear stability analyses of various interface equations in the long wavelength limit suggest these formations can result either from fluctuations in electrostatic forces between the fluid interface and induced image charge distribution,\footnote{S. Y. Chou and L. Zhuang, J. Vac. Sci. Technol. B 17, 3197 (1999)} radiation pressure induced by acoustic phonon reflections,\footnote{E. Sch\"affer \emph{et al}., Macromolecules 36, 1645 (2003)} or thermocapillary stresses leading to B\'enard-like deformations.\footnote{M. Dietzel and S. M. Troian, Phys. Rev. Lett. 103 (7), 074501 (2009); M. Dietzel and S. M. Troian, J. Appl. Phys. 108, 074308 (2010)} Here we review improvements over previous comparison to theoretical predictions\footnote{E. McLeod, Y. Liu and S. M. Troian, Phys. Rev. Lett. 106, 175501 (2011)} which suggest even closer agreement with the thermocapillary model; however, systematic discrepancies persist. We have therefore redesigned our experimental system for more accurate thermal flux control and estimation and will discuss our newest results.