Theoretical Investigation on the Electronic Structure of the Tris-(8-hydroxyquinolinato) Aluminum/Aluminum Interface

Abstract

We have studied the atomic geometries and the electronic properties of the tris-(8-hydroxyquinolinato) aluminum (Alq3)/Al interface by using density functional theoretical calculations. We examined three surfaces, the close packed Al(111) surface, the Al(332) stepped surface, and the Al adatom adsorbed Al(111) surface to investigate the effect of the surface roughness on the electronic properties of the interfaces. The calculated interface dipoles agree reasonably well with the experimental results and we found that the origin of the interface dipole formation mainly comes from the permanent dipole moment of Alq3 molecules. Although we have examined various possible structures, an interface gap state observed experimentally could not be reproduced by the present calculations.