THIN POLYMER-FILMS ON ROUGH SURFACES

X-ray diffraction measurements in the region of small incidence and ex it angles on thin polystyrene (PS) films deposited on laterally struct ured surfaces are performed. From fits of the data we obtain how the F ourier-components of the substrates are damped by the adsorbed films. The results are compared with theoretical predictions for liquid films . It turns out that PS-films of low molecular weight (less than or equ al to 300k) behave like frozen liquids. Within films of a molecular we ight of 1000k viscoelastic forces dominate over the substrate-adsorbat e van der Waals-interactions so that even a 680 Angstrom thick film is not totally flat on top of a grating with a height of 130 Angstrom.