Direct evidence of Al diffusion into tris-(8-hydroquinoline) aluminum layer: Medium energy ion scattering analysis

The diffusion of Al into tris-(8-hydroquinoline) aluminum (Alq3) was studied using in situ medium energy ion scattering (MEIS) spectroscopy. Al was thermally deposited on an Alq3 thin film in a stepwise manner, with MEIS performed after each deposition step. At the initial stage of interface formation, Al diffuses deep into the Alq3 layer and reaches the bottom of the Alq3 layer of thickness 20 nm. Some Al is stacked at the surface of Alq3 and starts to form an Al layer. The deep diffusion of Al is diminished when sufficient Al aggregates at the surface. After this stage, Al is stacked only at the surface, but does not diffuse into the Alq3 film.