title: Stability of Polymer Ultrathin Films (<7 nm) Made by a Top-Down Approach.
abstract: In polymer physics, the dewetting of spin-coated polystyrene ultrathin films on silicon remains mysterious. By adopting a simple top-down method based on good solvent rinsing, we are able to prepare flat polystyrene films with a controlled thickness ranging from 1.3 to 7.0 nm. Their stability was scrutinized after a classical annealing procedure above the glass transition temperature. Films were found to be stable on oxide-free silicon irrespective of film thickness, while they were unstable (<2.9 nm) and metastable (>2.9 nm) on 2 nm oxide-covered silicon substrates. The Lifshitz-van der Waals intermolecular theory that predicts the domains of stability as a function of the film thickness and of the substrate nature is now fully reconciled with our experimental observations. We surmise that this reconciliation is due to the good solvent rinsing procedure that removes the residual stress and/or the density variation of the polystyrene films inhibiting thermodynamically the dewetting on oxide-free silicon.
authors.affiliation: LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS , Le Mans Cedex 9, 72000, France.|Centre for Research in Nanoscience and Nanotechnology, University of Calcutta , Technology Campus, Block JD2, Sector III, Saltlake City, Kolkata, 700098, India.
authors.forename: Jayanta Kumar
authors.initials: JK
authors.lastname: Bal
authors.affiliation: LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS , Le Mans Cedex 9, 72000, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Beuvier
authors.affiliation: Laboratoire d'Ingénierie des MATériaux de Bretagne, Centre de Recherche , Rue de Saint Maudé, BP 92116, 56321 Lorient Cedex, France.
authors.forename: Aparna Beena
authors.initials: AB
authors.lastname: Unni
authors.affiliation: LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS , Le Mans Cedex 9, 72000, France.|European Synchrotron Radiation Facility , BP 220, 38044 Grenoble Cedex, France.
authors.forename: Elvia Anabela
authors.initials: EA
authors.lastname: Chavez Panduro
authors.affiliation: Laboratoire d'Ingénierie des MATériaux de Bretagne, Centre de Recherche , Rue de Saint Maudé, BP 92116, 56321 Lorient Cedex, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Vignaud
authors.affiliation: LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS , Le Mans Cedex 9, 72000, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Delorme
authors.affiliation: LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS , Le Mans Cedex 9, 72000, France.|Laboratoire d'Ingénierie des MATériaux de Bretagne, Centre de Recherche , Rue de Saint Maudé, BP 92116, 56321 Lorient Cedex, France.
authors.forename: Mohamed Souheib
authors.initials: MS
authors.lastname: Chebil
authors.affiliation: Laboratoire d'Ingénierie des MATériaux de Bretagne, Centre de Recherche , Rue de Saint Maudé, BP 92116, 56321 Lorient Cedex, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Grohens
authors.affiliation: LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS , Le Mans Cedex 9, 72000, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Gibaud
keywords: Hamaker constant; adsorbed or residual film; dewetting; free energy; solvent rinsing; stability; ultrathin film