AVS 46th International Symposium
    Organic Electronic Materials Topical Conference Tuesday Sessions
       Session OE+EM+AS-TuM

Paper OE+EM+AS-TuM9
Interfacial Electronic Structures between p-Sexiphenyl and Metals Studied by Electron Spectroscopies

Tuesday, October 26, 1999, 11:00 am, Room 616/617

Session: Interfaces and Characterization of Organic Thin Films
Presenter: E. Ito, Nagoya University, Japan
Authors: E. Ito, Nagoya University, Japan
H. Oji, Nagoya University, Japan
H. Ishii, Nagoya University, Japan
Y. Ouchi, Nagoya University, Japan
K. Seki, Nagoya University, Japan
Correspondent: Click to Email
Recently, organic electroluminecent (EL) devices have attracted much attention in relation to application to flat panel display. In order to understand the charge injection mechanism in such devices, the energy level alignment at the interfaces between organic films and metal electrodes is of crucial importance. In this study, we investigated electronic structures at the interfaces between p-sexiphenyl (6P) and a metal (Au or Mg) by ultraviolet photoelectron spectroscopy (UPS), metastable atom electron spectroscopy (MAES), and X-ray photoelectron spectroscopy (XPS). MAES is an extremely surface sensitive method because the excitation source is metastable atoms which can not penetrate into a sample. The abrupt shift of the vacuum level by 6P deposition on the evaporated metal film (Au or Mg) was observed in the UPS spectra. MAES spectrum of 6P on Au with the thickness of 0.3nm is almost similar with that of 20nm thick 6P film. This suggests that the flat-lying 6P molecules uniformly covered Au substrate. We also measured the spectra of Au on 6P/Au. Even when Au was evaporated with the thickness of 50nm, the spectral feature of 6P dominates in the MAES spectra, suggesting that Au does not cover completely with the 6P film, while the core level peak of Au gradually increased in XPS spectra with deposition of Au. Similar trend was also observed for Mg deposited on 6P/Mg. These results indicate the diffusion of Au into 6P film, leading to formation of the intermixing region. In the system of Au on 6P film, we observed downward shift of the energy levels with irradiation of UV-light (the excitati on source of UPS), probably due to the photovoltaic effect. These results show the the formation of the different interface between the 6P/metal and the metal/6P.