Maria Girleanu , Giulia Casula , Christian Blanck , Marc Schmutz , Christophe Contal , Navaphun Kayunkid , Piero Cosseddu , Annalisa Bonfiglio , Ovidiu Ersen , and Martin Brinkmann
J. Phys. Chem. C, 2015, 119 (23), pp 13115–13123
Publication Date (Web): May 22, 2015
Nucleation and growth of silver nanoparticles were studied on the surface of an n-type organic semi-conductor (N′-bis(n-octyl)-dicyanoperylene-3,4:9,10- bis(dicarboxyimide) (N1400)) as a function of the deposition rate τ and the substrate temperature Ts. Electron tomography was used to probe the bulk diffusion of Ag in the N1400 layers. No Ag nanoparticles are formed in the bulk of N1400 even for high substrate temperatures Ts = 125 °C, indicating that Ag diffusion in the organic semiconductor is marginal. The NPs distribution on the surface of N1400 is essentially determined by the surface roughness of the N1400 films. A transition in the nucleation mode of Ag NPs on N1400 is evidenced as a function of Ts: for Ts ≤ 50°C, Ag NPs form random patterns whereas for Ts ≥ 75 °C linear arrays of aligned NPs are observed. Such arrays result from step edge decoration of the N1400 terraces. The surface density of Ag NPs is thermally activated but the activation energy depends on the structure of the N1400 films: the smaller the crystal size of the N1400 grains, the larger the activation energy.