FTIR spectroscopic and STM studies of vacuum deposited aluminium (III) 8-hydroxyquinoline thin films

Abstract FTIR spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organization and morphology of vacuum deposited (VD) thin films of tris (8-hydroxyquinoline) aluminum (Alq3) from metal-organic planar light-emitting nanocomposites consisting of gold island films and VD Alq3 film. It was found that thermal evaporation in vacuum does not cause dissociation of Alq3, and that the obtained films are essentially amorphous. Reflection-absorption (RA) IR spectra show predominantly perpendicular orientation of quinoline groups of Alq3 molecules in the films towards the substrate. With the STM method, a thickness-dependent structure of the films was found and the first near-surface layers of Alq3 films were characterized. It has been revealed that VD deposited Alq3 films of small thickness (5–15 nm) consist of molecular domains with a particular orientation along the Au[112] direction.