Spintronic and multiferroic systems are leading candidates for achieving attojoule-class logic gates for computing, thereby enabling the continuation of Moore’s law for transistor scaling. However, ...shifting the materials focus of computing towards oxides and topological materials requires a holistic approach addressing energy, stochasticity and complexity.
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IJS, NUK, SBMB, UL, UM, UPUK
Multiple logic devices are presently under study within the Nanoelectronic Research Initiative (NRI) to carry the development of integrated circuits beyond the complementary metal-oxide-semiconductor ...(CMOS) roadmap. Structure and operational principles of these devices are described. Theories used for benchmarking these devices are overviewed, and a general methodology is described for consistent estimates of the circuit area, switching time, and energy. The results of the comparison of the NRI logic devices using these benchmarks are presented.
In this paper, we present a detailed performance comparison between conventional n-i-n MOSFET transistors and tunneling field-effect transistors (TFETs) based on the p-i-n geometry, using ...semiconducting carbon nanotubes as the model channel material. Quantum-transport simulations are performed using the nonequilibrium Green's function formalism considering realistic phonon-scattering and band-to-band tunneling mechanisms. Simulations show that TFETs have a smaller quantum capacitance at most gate biases. Despite lower on-current, they can switch faster in a range of on/off-current ratios. Switching energy for TFETs is observed to be fundamentally smaller than that for MOSFETs, leading to lower dynamic power dissipation. Furthermore, the beneficial features of TFETs are retained with different bandgap materials. These reasons suggest that the p-i-n TFET is well suited for low-power applications.
Since the early 1980s, most electronics have relied on the use of complementary metal-oxide-semiconductor (CMOS) transistors. However, the principles of CMOS operation, involving a switchable ...semiconductor conductance controlled by an insulating gate, have remained largely unchanged, even as transistors are miniaturized to sizes of 10 nanometres. We investigated what dimensionally scalable logic technology beyond CMOS could provide improvements in efficiency and performance for von Neumann architectures and enable growth in emerging computing such as artifical intelligence. Such a computing technology needs to allow progressive miniaturization, reduce switching energy, improve device interconnection and provide a complete logic and memory family. Here we propose a scalable spintronic logic device that operates via spin-orbit transduction (the coupling of an electron's angular momentum with its linear momentum) combined with magnetoelectric switching. The device uses advanced quantum materials, especially correlated oxides and topological states of matter, for collective switching and detection. We describe progress in magnetoelectric switching and spin-orbit detection of state, and show that in comparison with CMOS technology our device has superior switching energy (by a factor of 10 to 30), lower switching voltage (by a factor of 5) and enhanced logic density (by a factor of 5). In addition, its non-volatility enables ultralow standby power, which is critical to modern computing. The properties of our device indicate that the proposed technology could enable the development of multi-generational computing.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Circuits based on the stochastic evolution of nanoscale magnets have been used to split large numbers into prime-number factors -- a problem that only quantum computers were previously expected to ...solve efficiently.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
...the states persist despite random 'relaxation' forces caused by thermal fluctuations in the environment. ...random relaxation forces cause the nanomagnets to randomly fluctuate between the two ...states, with a certain probability that the net spin points up or down (Fig. 1c). ...the nanomagnet chip works at room temperature, whereas the quantum computer would need refrigeration to keep it well under 1 kelvin.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A new benchmarking of beyond-CMOS exploratory devices for logic integrated circuits is presented. It includes new devices with ferroelectric, straintronic, and orbitronic computational state ...variables. Standby power treatment and memory circuits are included. The set of circuits is extended to sequential logic, including arithmetic logic units. The conclusion that tunneling field-effect transistors are the leading low-power option is reinforced. Ferroelectric transistors may present an attractive option with faster switching delay. Magnetoelectric effects are more energy efficient than spin transfer torque, but the switching speed of magnetization is a limitation. This article enables a better focus on promising beyond-CMOS exploratory devices.
Active research is ongoing in logic devices beyond complementary metal–oxide–semiconductor electronics. One of the most promising classes of such devices is spintronic/nanomagnetic devices. Switching ...of magnetization by spin torque (ST) demonstrated in spintronic devices results in relatively high switching energy. An attractive option for lowering switching energy is magnetoelectric (ME) switching achieved by placing other materials (mostly oxides) adjacent to ferromagnets. We review recent experiments on ME switching, classify them according to the ME phenomena into surface anisotropy, exchange bias, and magnetostrictive, and compare switching parameters for these classes. Then, we perform micromagnetic simulations of switching by the effective ME field of both stand-alone nanomagnets and spintronic interconnects. We determine the threshold values of ME field for switching and the resulting switching time. These switching requirements are incorporated into the previously developed benchmarking framework for spintronic logic devices and circuits. We conclude that ME switching results in 1 to 2 orders of magnitude improvement of switching energy and several time improvement of switching delay compared with ST switching across various schemes of spin logic devices.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A spin-based logic device is proposed. It is comprised of a common free ferromagnetic layer and four discrete ferromagnetic nanopillars, each containing an independent fixed layer. It has the ...functionality of a majority gate and is switched via motion of domain walls by spin transfer torque. Validity of its logic operation and a quantitative performance prediction are demonstrated by micromagnetic simulation. It is entirely compatible with complimentary metal-oxide-semiconductor technology.
We have measured the spin torques of beta -tantalum/Co sub(20)Fe sub(60)B sub(20) bilayers versus Ta thickness at room temperature using a ferromagnetic resonance (FMR) technique. A significant ...fieldlike spin torque originating from Ta was identified, which is constant and independent of Ta thickness. Because of this constant torque, the spin Hall coefficient theta sub(SH) needs to be calculated from the ratio of the symmetric component of the FMR signal to the slope of the antisymmetric component with Ta thickness, from which a value of -0.11 + or - 0.01 was determined. The saturation magnetization of the CoFeB layers for samples deposited with Ta was found to be smaller than that of a single CoFeB layer, with values of 1.84 + or - 0.01 and 1.92 + or - 0.01 T, respectively. The origin of the fieldlike torque is ascribed to an interface spin-orbit coupling, or Rashba effect, due to the strength and constancy of the torque with Ta thickness. From fitting measured data to a semiclassical diffusion model that includes interface spin-orbit coupling, we have determined the spin diffusion length for beta -tantalum to be 2.5 nm.
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