Development of a Novel Inorganic Dielectric Barrier Layer for Magneto-Resistive Junctions

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Intellectual Merit: This research involves making and investigating high-resistivity B5C boron carbide as a major, new candidate for the dielectric barrier material in tunnel magnetoresistive devices. Based on their unique experience of making and using B5C in a variety of semiconductor applications, with chosen bandgaps from 0.9 to 2.7 eV, the investigators will use this material to help understand the fundamental properties of magnet/barrier interfaces that are highly important in magnetoelectronics and, specifically, spin electronics (spintronics) - one of the most promising future paths in electronics.The research team will use their abilities in spin-resolved photoemission to provide information on the surface electronic states and, since the dielectric film comprises such light atoms, to gain access to the important buried magnet/boron carbide interface. High-resolution electron microscopy and spectroscopy techniques will provide structural, dielectric, and bonding information on the B5C polytypes. Investigations of photoconductivity under applied magnetic fields will be used to gain better understanding of the influence of local impurity states in the barrier on magnetoresistance properties. Control of the orientation and polarization of the incident light will help identify these states and provide initial data for correlation with photoemission. Magnetic impurity atoms will be incorporated during dielectric growth in order to provide additional control of barrier states and so of magnetoresistance. Since initial results on chromium oxide junctions showed it is possible to modify the magnetic state of an island in the junctions by changing the polarity of the applied electric current, magnetic inclusions will also be incorporated in the barrier in order to test new ideas of spin transfer in non-oxide magnetic junctions.Broad Impacts: This project will train graduate and undergraduate students, particularly from underrepresented groups, in sophisticated experimental techniques and provide them with opportunities to communicate their results to peers, scientists and engineers in top journals and at major professional and industrial meetings. The research will allow the team to improve its capabilities for making boron carbide-based materials and devices, which have many applications, including neutron detection as two of the team recently demonstrated. Making magnetic sensors, or particle detectors, has become increasingly important for ensuring the security of our nation, and will continue to motivate the students on the team, and their peers. Opportunities will be sought to encourage understanding of the results, and their societal benefits, by people in business and industry, including through technology transfer, and by the general public, legislators and school students.The research will provide access to fundamental understanding of the physics of magnet/barrier interfaces and to practical technology for applying this understanding to spintronics. The additional device properties accessible by incorporating metallic inclusions in the barrier are expected to spur new magnetic memory applications.Most importantly, the research on boron carbide dielectric barriers is expected to provide a means of avoiding the serious reduction in the ferromagnet surface states caused by oxide dielectric barriers and therefore of avoiding a major problem for the development of spintronics. The research may therefore provide the basis for a key enabling technology for spintronics.