Improved Measurement of the 3D Dominant Mode Wavelength in NanoBenard Instability

Molten nanofilms exposed to an initial uniform and very large transverse thermal gradient ($10^5$ to $10^7$ C/cm) are prone to spontaneous formation and growth of nanopillars typically separated by tens of microns or less. Linear stability analysis of the corresponding interface equations suggest these formations result either from electrostatic attraction between the molten film and proximate substrate due to fluctuation induced surface image charge\footnote{S. Y. Chou and L. Zhuang, J. Vac. Sci. Technol. B 17, 3197 (1999)}, interface radiation pressure from coherent reflections of acoustic phonons\footnote{E. Sch\"affer \emph{et al}., Macromolecules 36, 1645 (2003)}, or fluctuation induced thermocapillary forces leading to 3D B\'enard-like structures\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)}. In this talk, we discuss a number of improvements to our original experimental system\footnote{E. McLeod, Y. Liu and S. M. Troian, Phys. Rev. Lett. 106, 175501 (2011)} including image analysis of structure formation at much earlier times. Our current measurements indicate even closer agreement with the thermocapillary mechanism proposed.