Investigation of the Interfaces of Tris-(8-hydroxyquinoline) Aluminum with Ag and Al Using Surface Raman Spectroscopy

2008-03-20T00:00:00Z (GMT) by Robert J. Davis Jeanne E. Pemberton
Surface Raman spectroscopy in ultrahigh vacuum is used to interrogate interfaces formed between tris-(8-hydroxyquinoline) aluminum (Alq<sub>3</sub>) and vapor-deposited Ag and Al. Vapor deposition of Ag onto Alq<sub>3</sub> films results in preservation of the Alq<sub>3</sub> structure with evolution of simple surface enhancement of Alq<sub>3</sub> spectral intensities. Changes in the relative intensities of ring breathing and ring stretching modes of Alq<sub>3</sub> upon deposition of Ag are consistent with weak interaction of Ag with the conjugated ring of the ligand. In contrast, vapor deposition of Al onto Alq<sub>3</sub> films results in the appearance of new vibrational modes, but only for Al coverages >10 Å mass thickness, consistent with the formation of an Al−Alq<sub>3</sub> adduct. At these coverages, slight surface enhancement of spectral intensities is also observed along with growth of several broad modes consistent with partial graphitization of the organic film.