Addressing the Challenges of Using Ferromagnetic Electrodes in Molecular Devices

Abstract

ABSTRACTFerromagnetic (FM) electrodes chemically anchored with thiol functionalized molecules can yield novel molecular spintronics devices (MSDs). However, significant challenges lie in developing commercially viable MSD fabrication approach utilizing FM electrodes. A practical MSD fabrication approach should consider FM electrodes’ susceptibility to oxidation, chemical etching, and stress induced deformations during fabrication and usage. This paper will discuss NiFe, an alloy used in the present day memory devices and high-temperature engineering applications, as a candidate for FM electrode and for the fabrication of MSDs. Our spectroscopic reflectance studies show that NiFe starts oxidizing aggressively beyond ∼90 ⁰C. The NiFe surfaces, aged for several months or heated for several minutes below ∼90 ⁰C, were suitable for chemical bonding with the thiol-functionalized molecules. NiFe also demonstrated excellent etching resistance in widely used dichloromethane solvent for dissolving molecular device elements. NiFe also reduced the mechanical stress induced deformities in other FM metals like cobalt. This paper also discusses the successful utilization of NiFe electrodes in the magnetic tunnel junction based molecular device fabrication approach. This research is expected to address the knowledge gap blocking the experimental development of FM based MSDs.