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

ABSTRACT: This study describes the evolution and growth of structured polymers by oblique angle deposition of poly(p-xylylene) (PPX) derivatives. The deposition of struc-tured PPX polymers have been demonstrated recently, but the mechanism of growth has not been studied. Here, we provide experimental evidence for the growth of struc-tured PPX polymers by an atomic force microscope, electron microscope, and a profi-lometer. Individual columns expand with respect to their heights according to a power-law, d chp, 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(trifloro-acetly-p-xylylene-co-p-xylylene), and poly(bromo-p-xylylene) films are estimated as 0.11 6 0.01, 0.15 6 0.01, and 0.18 6 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. Addi-tionally, the X-ray and transmission electron microscope characterization of the col-umns revealed that the columns are semicrystalline. VC 2008 Wiley Periodicals, Inc.