Photoelectron spectroscopy study of the electronic structures of Al/MgF2/tris-(8-hydroxyquinoline) aluminum interfaces

We have studied the electronic structures of Al/MgF2/tris-(8-hydroxyquinoline)aluminum (Alq(3)) interface using UV and x-ray photoelectron spectroscopy [(UPS) and (XPS), respectively]. The UPS revealed that the valence peak shift occurred with MgF2 deposition before Al was deposited and was independent of the gap state formation. The XPS core level peaks indicated that the MgF2 strongly interacted with Al and O atoms in Alq(3) even before Al was deposited, and the deposition of Al caused a slight change to the N 1s core level peak. These results indicate that the interaction mechanism in Al/MgF2/Alq(3) is different from those found in Al/LiF/Alq(3) and other metal/Alq(3). (C) 2001 American Institute of Physics.