To address device issues in WP1-3, the PI’s team investigated spin transport and reliability in large-scale chemical vapor-deposited graphene, a key ingredient for developing spin ICs. The research so far has led to several important publications from initial experiments. Studies on graphene spintronic devices gave new insights and implications of intricate surface charge transfer and sp3 -defects in Graphene/Metal Oxide Interfaces (ACS Appl Mater Interfaces 2022, 14 (31), 36209–36216), with new details of how ultrathin oxide layers titanium oxide (TiOx) and aluminum oxide (AlOx), used as tunnel barriers, impact graphene performance and spin relaxation in graphene, enabling a better understanding of the design of devices for performance. The results are supported by theory work from the project ‘“Resistive switching in graphene: A theoretical case study on the alumina-graphene interface” in Phys. Rev. Research 5, 043147, 2023.’ In this direction, another study of Large-scale direct growth of monolayer MoS2 on patterned Graphene channels for van der Waals ultrafast-photoactive circuits is under review in ACS Appl Mater Interfaces.
A critical aspect of interest for pure spin torque devices is graphene’s ability to conduct high current densities. Experiments from the PI’s team on CVD graphene have demonstrated the highest current carrying capacity of graphene ~ 5×108A/cm2 on Si/SiO2 and demonstrate spin transport at the highest current density 10^8A/cm^2 in graphene (Nano Res 16, 4233 (2023)), with further enhancement to ~ 1.7×10^9A/cm^2 on a diamond substrate with high thermal conductivity (to be communicated). Combining the knowledge of the above two works led to the development of a novel methodology to achieve scalable current-treated passive graphene (CTPG) (Nanoscale Horiz 9, 456 (2024)), where high current treatment of graphene surface passivated with oxide layers leads to enhance quality for achieving high-quality materials for scalable nanoelectronics and spintronics. This technique addresses the challenge of interfacial defects and remarkably improves carrier mobility, thereby reducing Coulomb scattering and mitigating potential issues such as electromigration. The success of this method in improving the electrical properties of graphene paves the way for its scalable application in advanced nanoelectronic and spintronic circuits. Overall, these results allow us to create high-performance and stable devices for advanced experiments in WP1 and WP2. The research in the direction of WP1 further led to the investigation of 2D magnets such as CrI3 (Phys Rev B 107, (2023) to understand fundamental excitations in 2D magnets.
The proposed research in WP3 has led to several significant results in ‘Proximity Enhanced Magnetism at NiFe2O4/Graphene Interface’ AIP Adv 12, (2022) and Surface Termination-Enhanced Magnetism at Nickel Ferrite/2D Nanomaterial Interfaces: Implications for Spintronics, ACS Appl Nano Mater 6, 10402 (2023). These publications bring new insights into how high spinterfaces can influence surface magnetization in 2D materials. Towards ultrafast demagnetization experiments have led to understanding Atom-Specific Magnon-Driven Ultrafast Spin Dynamics in Fe1-XNix Alloys, Phys Rev B 107, (2023). A novel experiment here has been the demonstration of gate voltage tunable ultrafast spin currents in graphene spinterface (graphene interfacing with magnets) junctions proposed in WP3.
