ENERGY-LEVEL ALIGNMENT AT ALQ METAL INTERFACES/

The energy level alignment for both Mg/8-hydroxyquinoline aluminum (Al q) and Au/Alq interfaces has been determined by the ultraviolet photoe mission measurements. For both interfaces, the difference between the Fermi level and the low-energy edge of the highest occupied molecular orbital (HOMO) is around 1.7 eV. This implies that the Fermi level wit h respect to the HOMO edge of Alq is independent of the work function of Mg and Au despite a large difference in the metal work function. A Fermi level alignment model is proposed, invoking a charge transfer be tween the metal and Alq and the formation of a dipolar layer at the me tal/Alq interface. (C) 1998 American Institute of Physics.