Metal nanostructures on top of Alq3 thin film: a GISAXS Story

Abstract

Poster presented at the 16th International Conference on Small-Angle Scattering, held on 13-18th September, 2015, Berlin (Germany).Tris(8-hydroxyquinolinato)aluminium (Alq3) is the active layer in most organic light emitting diodes (OLEDs), an important device as the next generation light source for illumination. Its low cost, easy fabrication and reasonable efficiency have attracted many research interests. The multilayer device structure emphasizes the significance of understanding the interfacial structure and properties. Metals (Al, Ag, et al.) are used as the metal electrical contact. Upon depositing on Alq3, metal atoms can diffuse into the organic layer, modifying both, the morphological and electronic structure, thereby affecting the final device performance. Al and Ag are known to interact with Alq3 differently as probed by different spectroscopic techniques[1–3] and theoretical method3. Nevertheless, the growth mechanism and morphology of Al and Ag on Alq3 is scarcely discussed. For this purpose, in situ grazing incident small angle X-ray scattering (GISAXS) plays a powerful role to characterize the inorganic/organic interfacial structure during the film growth process[4,5]. In this work, we have carried out an in-situ GISAXS characterization to monitor the entire process of Al and Ag metal thin film on top of Alq3 layer during the sputter depositionprocess [6,7]. Considering the different chemical reactivity of both uses metals, we have completely characterized the different growth mechanisms and final thin film structures: for Al, uniform nanopillar arrays develop; for Ag, the nanostructure morphology changes from truncated spheres to percolated layer. The results benefit the general comprehension of the development of metal/organic semiconductor interfacial structure prepared via sputtering process, which is widely used in the industry