Surface Roughness Scaling of Plasma Polymer Films

Atomic force microscopy data reveal self-affine scaling of plasma polymer films. The rms surface roughness σ increases with film thickness τ as σ(f<ξ^-1)~τ^β, and with measurement length L as σ(f>L^-1>ξ^-1)~L^α, where ξ is the surface roughness correlation length. At the deposition rate R=2 μmh, the scaling exponents α and β are 0.9 and 0.7, both increasing to 1 at R=2 μmh. A competition between surface relaxation and deposition rate determine α and ξ, which increase rapidly with R or inverse temperature.