Visualization of thermally-activated degradation pathways of tris(8-hydroxyquinoline) aluminum thin films for electroluminescence application

By exploiting variable-temperature tapping mode™ atomic force microscopy in O2 and N2, the thermally activated degradation pathways of the tris(8-hydroxyquinoline) aluminum (Alq3) thin film on indium-tin-oxide coated glass substrate have been studied as functions of temperature and time. Results suggest that the Alq3 thin film was thermally and chemically stable up to 125 °C in O2 and N2 atmospheres. No thermal oxidation of the thin film was detected by Fourier transform infrared spectroscopy. Apparent glass transition of the Alq3 thin film took place at 130 °C, well below the generally reported glass transition temperature of 170 °C or so. Crystallization of the Alq3 thin film occurred at 185 °C.