Thermal change of organic light-emitting ALQ3 thin films

A series of Alq3 thin films with the thicknesses of 50, 100, and 200 nm was deposited on Si substrates at room temperature using the thermal evaporation method. The thermal crystallization process of Alq3 thin films, especially 50 nm thick films, was successfully examined using high-temperature X-ray diffraction (HT-XRD) with the in-plane scan mode. Film thickness, density, and changes in surface roughness while heating were determined using X-ray reflectometry (XRR). The decreased density and increased surface roughness, which were accompanied by sublimation, indicate the instability of the Alq3 film. Thus, thermal instability is a major factor for device failure.