The electronic structures at the interface of aluminum tris(8-hydroxyquinoline) (Alq 3 )/Al 2 O 3 /Al have been determined by ultraviolet photoemission spectroscopy measurements and compared to similar measurements of the Alq 3 /Al interface. In the Alq 3 /Al 2 O 3 /Al study, shift of the highest occupied molecular orbital level of the Alq 3 layer was observed when compared to that of Alq 3 /Al. An energy level alignment diagram was proposed, showing that the lowering of the driving voltage achieved in organic electro-luminescent devices with a thin Al 2 O 3 layer between the aluminum cathode and the Alq 3 ®lm can be attributed to the reduction of the barrier height for electron injection. The electronic structures of Alq 3 grown on Ga and its oxide have also been studied. q 2000 Elsevier Science S.A. All rights reserved.

Synchrotron radiation photoelectron spectroscopy has been used to investigate III-V phosphide GaP and InP ͑100͒ surfaces treated with a neutralized (NH 4 ͒ 2 S solution. Compared to the conventional basic ͑NH 4 ͒ 2 S solution treatment, a thick sulfide layer with P-S bond and strong GaS ͑In-S͒ bond of high thermal stability is formed on the neutralized ͑NH 4 ͒ 2 S-treated GaP ͑InP͒ ͑100͒ surfaces. The possible passivation mechanisms of the two ͑NH 4 ͒ 2 S solutions to III-V phosphide surfaces are also discussed.

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