Power-law scaling of structured poly(p-xylylene) deposited by oblique angle

This study describes the evolution and growth of structured polymers by oblique angle deposition of poly(p-xylylene) (PPX) derivatives. The deposition of structured PPX polymers have been demonstrated recently, but the mechanism of growth has not been studied. Here, we provide experimental evidence for the growth of structured PPX polymers by an atomic force microscope, electron microscope, and a profilometer. Individual columns expand with respect to their heights according to a power-law, d = ch(P), where d is the column diameter, c and p are constants, and h is the height of a column. Values of p for structured poly(chloro-p-xylylene), poly(trifloroacetly-p-xylylene-co-p-xylylene), and poly(bromo-p-xylylene) films are estimated as 0.11 +/- 0.01, 0.15 +/- 0.01, and 0.18 +/- 0.01, respectively. This result is different from the traditional oblique angle deposition processes of nonpolymeric materials where the surface diffusion is low. Further analysis with two-dimensional power spectral density (PSD) method showed that the ordering of columns is quasi-periodic. Additionally, the X-ray and transmission electron microscope characterization of the columns revealed that the columns are semicrystalline. (C) 2008 Wiley Periodicals, Inc.