X-ray and VIS light scattering from light-induced polymer gratings

The development of light-induced polymer surface relief gratings (SRGs) inscribed onto polymer films containing photosensitive moieties is probed in situ by x-ray and visible (VIS) light scattering techniques. Both methods are complementary due to the different momentum transfer probed. The SRG appears with nearly perfect sinusoidal shape and amplitudes and is accompanied by a density grating (DG) below the surface. The time development of grating peak intensities for continuous and pulse like exposure is interpreted in terms of a new approach of kinematic scattering theory. The simulations demonstrate the extraordinary sensitivity of x-ray reflectivity for very small grating amplitudes (h < 5 nm), i.e. for the initial state of grating formation. VIS light scattering becomes sensitive if the grating amplitudes exceed about h = 10 nm. In particular, we find that the DG develops prior to SRG formation under actinic light.