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Comparative study of dielectric functions of complex organic heterostructures
Author(s) -
Gordan O. D.,
Hermann S.,
Friedrich M.,
Zahn D. R. T.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200541092
Subject(s) - heterojunction , superstructure , materials science , ellipsometry , dielectric , thin film , optoelectronics , analytical chemistry (journal) , chemistry , nanotechnology , organic chemistry , oceanography , geology
Organic/organic heterostructures and mixed layers were prepared by organic molecular beam deposition (OMBD) in high vacuum (HV) on hydrogen passivated (111) oriented silicon. The substrates were kept at room temperature during the deposition. The organic superstructures consisting in alternative layers of tris‐(8‐hydroxyquinoline)‐aluminum(III) (Alq 3 )/N,N′‐Di‐[(1‐naphthyl)‐N,N′‐diphenyl]‐(1,1′‐biphenyl)‐4,4′‐diamine (α‐NPD) and 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA)/copper phthalocyanine (CuPc) were investigated by means of spectroscopic ellipsometry in the 0.73–5 eV spectral range. Additionally reflection infra‐red (IR) measurements were performed using p‐ and s‐polarisation. Taking into account the dielectric function of the single layers the optical response of the Alq 3 /α‐NPD superstructure can be modeled assuming sharp interfaces. However, for the PTCDA/CuPc superstructure the optical response requires a more sophisticated approach than simply superimposing the responses of the individual layers. The deviation between simulated and experimental data is assigned to the molecular interaction at the interfaces between PTCDA and CuPc. This can affect the molecular orientation and the optical properties. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)