Probing thermomechanical behavior of polymers at the nanometer scale with single-ion bombardment and scanning force microscopy

Features produced by swift heavy ions on polymer thin films at different temperatures are used to identify the transition between vitreous and viscoelastic behaviors (the glass transition temperature) and to probe the relaxation of nanodeformations in the material. Scanning force microscopy images reveal nanometer-sized craters and raised regions around the point of ion impact. The size of such defects is independent of temperature for $-196°\mathrm{C}<T<\mathrm{}80\mathrm{}°\mathrm{C},$ but above a critical temperature crater dimensions increase steeply and no plastic deformation is observed. This critical temperature is sensitive to the cooling rate, and for rapidly cooled targets it is close to the glass transition temperature of the polymer.