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Relaxation times of nanoscale deformations on the surface of a polymer thin film near and below the glass transition

We report on measurements of relaxation times of nanometer-sized deformations resulting from the impact of individual energetic ions on poly(methyl methacrylate) surfaces at temperatures close to and below the glass transition T{sub g}. The temporal evolution of the dimensions of the deformations is well described by a stretched exponential function, but with relaxation times {tau}(T) many orders of magnitude smaller than bulk values at the same T. The local T{sub g} was around 86 deg. C, roughly 30 deg. C below the conventional bulk T{sub g}. At the vicinity of the local T{sub g}, {tau}(T) follows the Vogel-Fulcher type of T dependence, but at lower T a transition towards a less steep behavior is seen.