Photoemission spectroscopy investigation of magnesium-Alq₃ interfaces

The formation of interfaces between magnesium (Mg) and the organic molecular semiconductor tris(8-hydroxy-quinoline) aluminum (Alq₃) is studied via ultraviolet photoemission spectroscopy. The morphology and electronic structure of Mg-on-Alq₃ and Alq₃-on-Mg interfaces are compared. The energy of the Alq₃ molecular levels is determined in both cases with respect to a reference Fermi level as a function of interface formation. The difference in injection characteristics between the two interfaces is examined in terms of differences in interface morphology and of electronic gap states induced by the diffusion of Mg at the Mg/Alq₃ interface.