Decay kinetics of nanoscale corrugation gratings on polymer surface: Evidence for polymer flow below the glass temperature

The near-surface rheology of polystyrene films at temperatures around T-g was probed via the decay kinetics of shallow, nanoscale surface corrugation gratings. The gratings were created via hot embossing with a stepped silicon template. The wavelengths are distributed in a range between 25 and 60 nm and have a modulation depth of about 0.8 run peak-to-peak. Upon heating, one observes a surface tension-driven decay of the surface corrugation at temperatures more than 30 deg below the bulk Tg. Such a fast decay is unexpected and indicates a strongly lowered glass temperature near the surface.