Surface Roughness Scaling of Plasma Polymer Films

Atomic force microscopy data reveal self-affine scaling of plasma polymer films. The rms surface roughness $\sigma$ increases with film thickness $\tau$ as $\sigma (f<\mathrm{}{\xi }^{-1\mathrm{}})\sim {\tau }^{\beta }$, and with measurement length $L$ as $\sigma (f>\mathrm{}{L}^{-1\mathrm{}}>{\xi }^{-1\mathrm{}})\sim L^{\alpha }$, where $\xi$ is the surface roughness correlation length. At the deposition rate $R=2\mathrm{} \frac{\mu m}{h}$, the scaling exponents $\alpha$ and $\beta$ are 0.9 and 0.7, both increasing to 1 at $R=2\mathrm{} \frac{\mu m}{h}$. A competition between surface relaxation and deposition rate determine $\alpha$ and $\xi$, which increase rapidly with $R$ or inverse temperature.