Among the promising ideas emerging from the organic electronic, one is to develop electronic
devices with both metals and organic materials which are grown on flexible substrates [1]. The
range of such industrial applications is huge. It concerns, for instance, flexible screens but also
flexible sensors. In 1996, Parkin [2] showed that “giant magnetoresistive” sensors can be grown of organic substrates or on thin organic films deposited on silicon substrates. Another kind of system commonly used for spintronic applications is the magnetic tunnel junction. Two ferromagnetic metals are then separated by a very thin insulator which acts as a tunnel barrier. An important change in the electrical resistance is expected when the two magnetizations switch from a parallel to an anti-parallel configuration. It is the so-called tunnel magnetoresistance (TMR) effect. We report on the fabrication and electrical characterization of micrometric MTJs grown on organic thin films spin-coated on silicon. The polymer used as organic buffer layer is the widespread PEDOT-PSS. PEDOT-PSS (Poly(3,4-ethylenedioxythiophene)poly-styrenesulfonate) is a flexible organic layer widely used in organic electronics. We have grown by sputtering technique standard Co/Al₂O₃/Co magnetic tunnel junctions on the PEDOT:PSS organic buffer layer and on a reference Si/SiO2substate. MTJs with large area (0.3*0.3 mm²) have been studied in order to test the homogeneity of the thin Al₂O₃ (2.5 nm) tunnel barrier. First the roughness and local conductance of Co/Al₂O₃ bilayers have been characterized by a conductive tip AFM in order check the low roughness and the absence of short-circuit required for working MTJs. Co/Al₂O₃ bilayers grown on PEDOT:PSS and Si/SiO₂ substrate show a very low roughness about 0.6 nm and similar local conductance and without pinholes. Studies of the spin dependent transport show similar TMR for MTJ grown on PEDOT:PSS and on Si/SiO₂. This study shows the ability to conserve spin dependent transport properties of spintronics devices grown on an organic substrate.

[1] S.R. Forrest, Nature, Vol. 428, 911 (2004)
[2] S.S. Parkin, Appl. Phys. Lett. 69, 20 (1996)

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