Roughness of molecularly thin perfluoropolyether polymer films

X-ray reflectivity has been used to measure the roughness of perfluoropolyether (PFPE) polymer films on silicon substrates and carbon overcoats. For PFPE on smooth silicon, we find that the rms roughness of the PFPE-air interface increases slowly from about 2 to 4 Angstrom as PFPE thickness increases from 5 to 33 Angstrom. This increase is consistent with capillary waves roughening the polymer film, but inconsistent with current theories for the dewetting of polymer films. For PFPE on the rougher surface of amorphous hydrogenated carbon, we find that the PFPE polymer smoothes the surface with the rms roughness decreasing from 9 to 4 Angstrom. We also discuss the implications of these results on the limits of disk drive technology. (C) 2000 American Institute of Physics. [S0003-6951(00)05046-4].