Preparation and properties of hybrid bilayer structures based on organic Alq3, ferromagnetic La2/3Sr1/3MnO3 and Fe3O4

We report preparation and properties of hybrid bilayer structures composed of the organic semiconductor, 8-hydroxyquinoline aluminum (Alq3), p-type Si and two ferromagnetic oxides, namely, colossal magnetoresistance manganite, La2/3Sr1/3MnO3 (LSMO), and magnetite (Fe3O4). Thin Alq3 films were thermally evaporated in vacuum. The bottom LSMO films were grown in-situ at 750 degrees C by dc magnetron sputtering on crystalline SrTiO3 while Fe3O4 films were magnetron sputtered at 400 degrees C on glass. Current versus voltage in a case of vertical current flow has been investigated for the heterojunctions. The investigations revealed dominating role of thermoionic emission in a barrier of Schottky type for the Alq3/p-Si heterojunction while a mechanism based on carrier tunnelling through an interface and space charge limited current processes were considered to explain nonlinear electrical transport in the Alq3/LSMO, Alq3/Fe3O4 heterojunctions. The Alq3/LSMO demonstrated magnetoresistance values up to 11 % (at T = 240 K and B = 1 T).