Ionization-assisted deposition of Alq(3) films

Thin films of 8-hydroxyquinoline aluminum, which is an important light emitting material for organic electroluminescence (EL) devices, were deposited by use of an ionization-assisted deposition method. The deposited film had an amorphous structure and indicated the identical infrared absorption spectra as the source material. These properties were not influenced by the ion energy up to 5050 eV under ion current densities of 20 to 30 nA cm(-2). The X-ray photoelectron spectroscopy (XPS) analysis suggested that oxygen-related impurity can be reduced by applying the ion acceleration voltage of around 350 V. Photoluminescence intensity was also influenced by the ion energy, and had a correlation with the XPS result; a film of lower oxygen impurity showing higher luminescence intensity. The ionization-assisted deposition seems to be a promising method for film deposition of organic EL materials, due to the capability of reducing the impurity incorporation and improving the luminescence characteristics.