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Energy Level Alignment at Tpd/Etal Interfaces Studied by Kelvin Method

Published online by Cambridge University Press:  10 February 2011

N. Hayashi ,
E. Ito ,
H. Ishii ,
Y. Ouchi  and
K. Seki
N. Hayashi
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
E. Ito
Affiliation:
Venture Business Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan e-mail: ito@mat.chem.nagoya-u.ac.jp
H. Ishii
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
Y. Ouchi
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
K. Seki
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
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Abstract

The vacuum level shift A was determined by Kelvin probe method for TPD/metal systems prepared in ultrahigh vacuum (TPD: N, N'-bis(3-methylphenyl)-N, N'-diphenyl-[1, 1'-biphenyl]-4,4'-diamine). The energy of the vacuum level sharply changed at the initial stage of depositing TPD on the metal substrates, and further bending was not observed up to 100 nm thickness of TPD. This result is consistent with our previous studies of ultraviolet photoelectron spectroscopy. These results indicate the invalidity of traditional model with a common vacuum level at organic/metal interface. We discussed the dependence of the vacuum level shift on the work function Φm of the metal substrate (Au, Cu, Ag, Mg, and Ca). A liner correlation between Δ and Φm was observed only in the region of 3.8 eV < Φm < 4.5 eV, indicating that Fermi level alignment is not achieved at least for some interfaces. We found that Δ for TPD film on the air-exposed metal substrate is smaller than that of TPD on clean metals and was observed a liner relation between Φm and Δ except for the Cu substrate.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 558: Symposium B – Flat-Panel Displays and Sensors-Principles, Materials… , 1999 , 445
Copyright
Copyright © Materials Research Society 2000

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References

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