In situ study on layer-by-layer growth in vapor deposition of linear long-chain molecules using a quartz crystal microbalance

The thin film formation at the initial stage of the vapor deposition of organic long-chain molecules was monitored using a quartz crystal microbalance. The growth rate of the thin films was strongly dependent on the substrate temperature: at substrate temperatures below 287 K, the film growth proceeded at a uniform rate while no film was formed above 297K owing to a higher rate of re-evaporation. Of particular interest is a stepwise increase in the amount of molecules adsorbed at 293 K, where each step height corresponded to the molecular length. These results suggest that layer-by-layer growth proceeds with a molecular orientation normal to the substrate under the conditions where re-evaporation dominates the film growth process. This growth model was confirmed by fitting the data to the Avrami equation for the two-dimensionally predetermined nucleation. (c) 2013 AIP Publishing LLC.