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

By exploiting variable-temperature tapping modeTM 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 deg. 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 deg. C, well below the generally reported glass transition temperature of 170 deg. C or so. Crystallization of the Alq3 thin film occurred at 185 deg. C