Structure of Co/Alq3 bilayers: X-ray reflectivity study

In the present paper, we report on the structural investigation of ferromagnetic metal/organic semiconductor bilayer thin films. Ferromagnetic Co thin films with thickness ∼ 150 A were deposited on organic semiconductor Tris-(8-hydroxyquinoline)aluminum, Alq3 thin films with different thickness ranging from 250 A to 900 A. Alq3 thin films were deposited on Si(100) substrates by thermal evaporation prior to the deposition of Co thin films using electron beam evaporation technique. X-ray reflectivity measurements have been performed to determine the internal structure of the bilayer samples. Experimental reflectivity data were fitted using Parratt formalism to gain information about thickness, electron density, and roughness of the individual layer. X-ray reflectivity analysis confirms about 13 nm diffusion of Co into underneath Alq3 layer at the Co/Alq3 interface. It is not possible to clarify whether diffused Co is in the form of atoms or as clusters from the x-ray reflectivity analysis.