Fragmentation and adhesion properties of CoFeB thin films on polyimide substrate

Abstract

We have studied the electro-mechanical properties of 20 nm thick CoFeB thin films deposited on Kapton® substrate by electrical resistivity measurements and atomic force microscopy observations during in situ tensile tests. We show in this paper that the amorphous CoFeB thin film has a brittle behavior with crack initiation at 1.6%. Moreover, the partial reversibility of the resistivity curve depends on the maximum applied strain because of the plastic deformation of the Kapton® up to 5%. Finally, the adhesion energy between CoFeB and Kapton® has been estimated from the geometry of buckling induced by the transverse compressive stress occurring during the fragmentation test. This study shows that adhesion is good enough for considering this system for potential applications in flexible spintronics applications.