Periodic Reporting for period 2 - SPINNER (Spin Engineering in Flexible and Functional Two-Dimensional Quantum Material Devices)
Periodo di rendicontazione: 2023-03-01 al 2024-08-31
The emerging class of atomically thin materials like graphene and other two-dimensional (2D) quantum materials provides unprecedented means for exploring and exploiting the physical phenomena of electron spin (magnetic moment). SPINNER aims to design and realize experiments to determine how to control spin phenomena involving spin currents and spin order (magnetism), how fast and efficiently one can control them, and realize their novel spin components. SPINNER aims to achieve the ultimate engineering of spin currents and magnetism by tuning interatomic separations in 2D quantum crystals. Employing these systems and phenomena, SPINNER explores new spin functions and experiments to uncover their ultimate power efficiency and operation speeds.
With an ever-increasing need for computation and the Internet of Things (IoT), electronic devices are predicted to consume 40% of global power output by 2030, making innovation for low-power electronics an inescapable problem for human society's sustainable progress. The project ‘Spin Engineering in Flexible and Functional Two-Dimensional Quantum Material Devices’ is about making fundamental advances towards enabling spin integrated circuits that can operate with ultralow power at ultrafast speeds and making electronics intelligent at the component level. The societal impacts include a significant reduction in energy consumption in electronic devices and the development of novel neuromorphic hardware for advancing artificial intelligence.
To scientifically address the purpose of SPINNER, the following objectives are addressed in the project.
Objective 1. Strain engineering of spin phenomena in 2D materials, by which one can not only tune charge and spin transport in 2D materials but also control magnetism in two dimensions.
Objective 2. Field-free Pure Spin Torque (PST) functionality in graphene spin circuits to realize field-free manipulation of nanomagnetism and magnetic domain walls and establish the power of charge-less spin currents.
Objective 3. Ultrafast spin dynamics in 2D spinterfaces to determine speed capabilities of spin currents for ultrafast spin ICs.
Since SPINNER's inception, work has been performed in all work packages, which have resulted in several key publications and results, as summarized below.
With an ever-increasing need for computation and the Internet of Things (IoT), electronic devices are predicted to consume 40% of global power output by 2030, making innovation for low-power electronics an inescapable problem for human society's sustainable progress. The project ‘Spin Engineering in Flexible and Functional Two-Dimensional Quantum Material Devices’ is about making fundamental advances towards enabling spin integrated circuits that can operate with ultralow power at ultrafast speeds and making electronics intelligent at the component level. The societal impacts include a significant reduction in energy consumption in electronic devices and the development of novel neuromorphic hardware for advancing artificial intelligence.
To scientifically address the purpose of SPINNER, the following objectives are addressed in the project.
Objective 1. Strain engineering of spin phenomena in 2D materials, by which one can not only tune charge and spin transport in 2D materials but also control magnetism in two dimensions.
Objective 2. Field-free Pure Spin Torque (PST) functionality in graphene spin circuits to realize field-free manipulation of nanomagnetism and magnetic domain walls and establish the power of charge-less spin currents.
Objective 3. Ultrafast spin dynamics in 2D spinterfaces to determine speed capabilities of spin currents for ultrafast spin ICs.
Since SPINNER's inception, work has been performed in all work packages, which have resulted in several key publications and results, as summarized below.
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.
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.
The experiments in SPINNER have so far led to realizing the highest current carrying capacity in CVD graphene with beyond-state-of-the-art performance, developing a novel methodology of current-treated passivated graphene, and demonstrating the first electric field-controlled spin currents in graphene spinterfaces.
With developments of experiments ongoing during the project, the following experiments and results are anticipated.
(1) Strain-Spin correlation in 2D materials, with insights into strain dependence of spin transport in graphene and MoS2, and strain engineering of 2D magnets, allowing control of magnetism with tunable interatomic distances.
(2) first-time spin current-assisted magnetization manipulation demonstration.
(3) first demonstration of pure spin current-induced magnetic domain wall propagation and novel physics of field-free magnetization manipulation in nanomagnets and domain walls, with potential for energy efficiency using pure spin currents.
(4) Building on existing results on ultrafast spin currents, experiments to control such currents in magnetic-tunnel junctions involving 2D materials are expected to lead to new bias-dependent control of ultrafast demagnetization and switching.
With developments of experiments ongoing during the project, the following experiments and results are anticipated.
(1) Strain-Spin correlation in 2D materials, with insights into strain dependence of spin transport in graphene and MoS2, and strain engineering of 2D magnets, allowing control of magnetism with tunable interatomic distances.
(2) first-time spin current-assisted magnetization manipulation demonstration.
(3) first demonstration of pure spin current-induced magnetic domain wall propagation and novel physics of field-free magnetization manipulation in nanomagnets and domain walls, with potential for energy efficiency using pure spin currents.
(4) Building on existing results on ultrafast spin currents, experiments to control such currents in magnetic-tunnel junctions involving 2D materials are expected to lead to new bias-dependent control of ultrafast demagnetization and switching.