Investigation of the interfaces of tris-(8-hydroxyquinoline) aluminum with Ag and Al using surface Raman spectroscopy

Raman spectroscopy in ultrahigh vacuum is used to interrogate interfaces formed between tris-(8-hydroxyquinoline) aluminum (Alq(3)) and vapor-deposited Ag and Al. Vapor deposition of Ag onto Alq(3) films results in preservation of the Alq(3) structure with evolution of simple surface enhancement of Alq(3) spectral intensities. Changes in the relative intensities of ring breathing and ring stretching, modes of Alq(3) 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(3) films results in the appearance of new vibrational modes, but only for Al coverages > 10 angstrom mass thickness, consistent with the formation of an Al-Alq(3) adduct. At these coverages, slight surface enhancement of spectral intensities is also observed alone, with growth of several broad modes consistent with partial graphitization of the organic film.