Articolo in rivista, 2012, ENG

Morphology and molecular orientation in sexithiophene and N,N '-bis (n-octyl)-dicyanoperylenediimide heterostructures

Tkachenko, V1; Di Girolamo, FV1; Chiarella, F2; Cassinese, A1; Abbate, G1

1Università di Napoli Federico 2, CNR SPIN, I-80126 Napoli 2Università degli Studi di Salerno, CNR SPIN I-84084 Fisciano Salerno

We report on the growth mode of N,N'-bis (n-octyl)-dicyanoperylenediimide (PDI-8CN(2)) on sexithiophene (T6) thin films, studied with different structural, morphological and optical techniques. We aim to individuate the most favorable conditions for the realization of heterostructure devices. The crystalline quality was established by X-ray patterns and Atomic Force Microscopy (AFM) images, and found to be generally high. The anisotropic optical constants extracted from ellipsometry measurements shed light on the mean molecular orientation in the PDI-8CN(2) film. AFM images evidence two different growth modes: at T6 thickness less than 2 monolayers (ML), the growth of PDI-8CN(2) on T6 is favored with respect to SiO2, while, at higher thickness (2-6 ML), the situation is reversed. An optimum T6 underlayer thickness of approximately 1 ML provides the best quality of PDI-8CN(2) layer corresponding to the highest island dimension, the highest molecular order parameter, and the lowest roughness. Spectrum broadening was observed for extinction coefficient of PDI-8CN(2) in the heterostructures, as compared with a sole material film, and explained by two effects: increase in molecular disorder and formation of charge transfer complexes.

Thin solid films (Print) 520 (7), pp. 2390–2394

Keywords

CNR authors

Abbate Giancarlo, Cassinese Antonio, Chiarella Fabio, Tkachenko Volodymyr

CNR institutes

SPIN – Istituto superconduttori, materiali innovativi e dispositivi, SPIN – Istituto superconduttori, materiali innovativi e dispositivi