Plasma-Treated Bottom Electrode-Based Molecular Spintronic Device Fabrication for Extremely High Switching

Tunneling magnetoresistance (TMR) is a quantum mechanical phenomenon and an important effect that happens in magnetic tunnel junctions (MTJ). TMR reaches its maximum value when electrodes’ spins take parallel orientations with respect to each other. Along with bias voltage, barrier type and thickness, and structural asymmetry in MTJs, electrodes’ quality play an important role in gaining high TMR in molecular spintronic devices. A defect-free tunnel barrier reduces the charge transport competing effect by the insulator and enhances the transport via conducting molecular channels. This work investigates the fabrication defects of MTJ tunnel barriers caused by the bottom electrode and uses various strategies to minimize and remove those defects through different techniques. We used the Taguchi Design of Experiment, Oxygen plasma cleaning, and Argon Etching to minimize interlayer coupling between ferromagnetic electrodes. Our results showed a significant difference in bottom electrode edge geometry and surface roughness upon post-lift-off Ar Etch compared to other techniques. We observed an extremely high switching ratio (~1000 times increase in TMR) upon removal of pinhole-type defects and hillocks in our SMM-based molecular spintronic device. IV measurements, MFM, and KPFM scans support the improvements of the device characteristics after fabrication optimization.