Temperature dependence of the growth front roughening of oligomer films

Growth front roughening characteristics of vacuum deposited pentamer 2,5-di-n-octyloxy-1,4-bis[4-(styryl)styryl]-benzene oligomer thin films, onto silicon substrates, strongly depend on the substrate temperature in the range ∼20 °C–100 °C. The measured roughness exponents H increase from H≈0.4 at low substrate temperatures where growth is dominated by vacancy formation, to H≈0.7–0.8 at elevated temperatures where diffusive growth takes place. Moreover, the root-mean-square roughness amplitude and the correlation length evolve with temperature closely as an Arrhenius process with activation barrier comparable to molecule transnational and rotational barriers on oligomer surfaces.