Splitting-induced surface patterns on the surface of polystyrene thin films

The effects of UV irradiation and molecular weight on the splitting-induced surface gratings on the surface of PS films sandwiched between two silicon plates have been studied, using the tension-splitting and peeling-splitting methods. Both the spatial wavelength and amplitude of the surface gratings increase linearly with the increase of the film thickness, independent of the UV irradiation dose and molecular weight. The average differential ratio (slope) of the spatial wavelength to the film thickness decreases with the increase of the UV irradiation dose for both the splitting methods. Both the UV irradiation and molecular weight have no effect on the trend that the apparent surface stress on the surface of the PS films increases with the increase of the film thickness. Sandwiched structures with a PMMA-based photoresist film and a PS film of about the same thickness sandwiched between two silicon plates have been prepared. Surface gratings have been made from the bilayer-sandwiched structures using the peeling-splitting method. For the surface gratings solely made from PS or a photoresist of the bilayer-sandwiched structures, both the spatial wavelength and amplitude of the surface gratings increase linearly with the increase of the film thickness.