Direct evidence for interaction of magnesium with tris(8-hydroxy-quinoline) aluminum

The interaction between magnesium (Mg) and tris(8-hydroxy-quinoline) aluminum (Alq₃) has been studied using high-resolution electron energy-loss spectroscopy (HREELS). It was found that deposition of magnesium on the Alq₃ film gave rise to clear changes in the HREELS spectra. The changes are attributed to the weakly bounded Mg atoms on the Alq₃ layer. Interestingly, for a given amount of magnesium (Mg to Al atoms ratio=3) on Alq₃ film, remarkable changes were observed in the HREELS spectra when the sample was heated. A loss peak at 81 meV, which was assigned to Mg-O stretch mode, appeared upon annealing and increased in intensity as the annealing temperature increased up to about 360 K. This suggested that the diffusion of Mg atoms into the Alq₃ layer and the reaction between Mg and Alq₃ molecule occurred at the temperature range investigated. The present work has provided direct evidence for the strong interaction between magnesium and Alq₃. © 2000 American Institute of Physics.