Growth front roughening of room-temperature deposited oligomer films

Growth front scaling aspects are investigated by atomic force microscopy for oligomer 2,5-di-n-octyloxy-1,4-bis(4′-(styryl)styryl)-benzene thin films vapor deposited onto silicon substrates at room temperature. Analyses of the height–height correlation function for film thickness that are commonly used in optoelectronic devices, i.e., ranging between 15 and 300 nm, yield roughness Hurst exponents around H=0.45±0.04. Further, the root-mean-square roughness amplitude σ evolves with film thickness as a power law σ∝dβ, with β=0.28±0.05. The nonGaussian height distribution and the measured scaling exponents (H and β) suggest a roughening mechanism close to that described by the Kardar–Parisi–Zhang [Phys. Rev. Lett. 56, 889 (1986)] scenario indicating nonlinear film growth.