Deposition of cobalt atoms ontoAlq3films: A molecular dynamics study

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The charge and spin injections into semiconductors are determined by the quality of the electrode/semiconductor interface. The latter is defined by the atomic penetration depth when growing metal electrodes on organic semiconductor thin films by the physical deposition method. Although the interfaces between top electrodes and a typical organic material, tris(8-hydroxyquinoline) aluminum $({\mathrm{Alq}}_{3})$ thin films, have been intensively investigated by several groups, their results on the atomic penetration depth into ${\mathrm{Alq}}_{3}$ film diverged from each other. In this paper we study the deposition of cobalt atoms onto ${\mathrm{Alq}}_{3}$ thin films using the molecular dynamics method. The intermixing between Co and ${\mathrm{Alq}}_{3}$ is calculated to be limited to the first ${\mathrm{Alq}}_{3}$ layer for low Co initial kinetic energies, but spread to a few layers for high initial energies. The results of our calculation indicate that a proper deposition method with low injection energy helps to reduce the amount of intermixing at interfaces and improve the magnetoresistance of an organic-based magnetic junction.