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Proceedings Paper

Energy level alignment and band bending at organic interfaces
Author(s): Kazuhiko Seki; Hiroshi Oji; Eisuke Ito; Naoki Hayashi; Yukio Ouchi; Hisao Ishii
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Paper Abstract

Recent progress in the study of the energy level alignment and band bending at organic interfaces is reviewed, taking the examples mainly from the results of the group of the authors using ultraviolet photoelectron spectroscopy (UPS), metastable atom electron spectroscopy (MAES), and Kelvin probe method (KPM). As for the energy level alignment right at the interface, the formation of an electric dipole layer is observed for most of the organic/metal interfaces, even when no significant chemical interaction is observed. The origin of this dipole layer is examined by accumulating the data of various combinations of organics and metals, and the results indicate combined contribution from (1) charge transfer (CT) between the organic molecule and the metal, and (2) pushback of the electrons spilled out from metal surface, for the case of nonpolar organic molecule physisorbed on metals. Other factors such as chemical interaction and the orientation of polar molecules are also pointed out. As for the band bending, the careful examination of the existence/absence of band bending of purified TPD* molecule deposited on various metals in ultrahigh vacuum (UHV) revealed negligible band bending up to 100 nm thickness, and also the failure of the establishment of Fermi level alignment between organic layer and the metals. The implications of these findings are discussed, in relation to the future prospects of the studies in this field. (*:N,N'- diphenyl-N,N'-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine).

Paper Details

Date Published: 17 December 1999
PDF: 11 pages
Proc. SPIE 3797, Organic Light-Emitting Materials and Devices III, (17 December 1999); doi: 10.1117/12.372708
Show Author Affiliations
Kazuhiko Seki, Nagoya Univ. (Japan)
Hiroshi Oji, Nagoya Univ. (Japan)
Eisuke Ito, Nagoya Univ. (Japan)
Naoki Hayashi, Nagoya Univ. (Japan)
Yukio Ouchi, Nagoya Univ. (Japan)
Hisao Ishii, Nagoya Univ. (Japan)

Published in SPIE Proceedings Vol. 3797:
Organic Light-Emitting Materials and Devices III
Zakya H. Kafafi, Editor(s)

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