2D materials for spintronic devices
Ethan C. Ahn
npj 2D Materials and Applications volume 4, Article number: 17 (2020) Cite this article

[Abstract]
2D materials are attractive for nanoelectronics due to their ultimate thickness dimension and unique physical properties. A wide variety of emerging spintronic device concepts will greatly benefit from the use of 2D materials, leading a better way to manipulating spin. In this review, we discuss various 2D materials, including graphene and other inorganic 2D semiconductors, in the context of scientific and technological advances in spintronic devices. Applications of 2D materials in spin logic switches, spin valves, and spin transistors are specifically investigated. We also introduce the spin-orbit and spin-valley coupled properties of 2D materials to explore their potential to address the crucial issues of contemporary electronics. Finally, we highlight major challenges in integrating 2D materials into spintronic devices and provide a future perspective on 2D materials for spin logic devices.

[ Introduction]
The unprecedented success of silicon-CMOS technology has been primarily driven by transistor scaling. The early era of Dennard scaling1,2 had two important consequences for modern computing systems; speed performance has been improved by scaling of physical dimensions while power density has been kept practically constant by scaling of voltages. However, since around 2005, the voltage scaling has become a challenging task3 because further reduction of the supply voltage (requiring the threshold voltage to be simultaneously decreased to maintain the capability to drive high current) was leading to an exponential increase in the leakage current. This is due to the fundamental limit of subthreshold swing (SS) greater than 60?mV/decade at room temperature, which arises from the Boltzmann statistics that govern the thermionic operation of conventional MOSFETs4. Although tunnel FETs5,6,7, negative capacitance FETs8,9,10, and electrostrictive FETs11,12 have recently emerged as novel device concepts for steep SS, they still require much work to improve the device performance and/or answer fundamental questions on scalability, reliability, and viability. On the other hand, scaling of physical dimensions still continued until today, towards the technology nodes of 5?nm and beyond13,14. This led to an inevitable increase in power density in high-performance microprocessors, thus requiring complex power management techniques15,16. In view of this, spintronics, which utilizes the quantum mechanical property of elementary particles, called spin, has the potential to become an innovative pathway beyond transistor scaling to satisfying the speed and energy-efficiency needs of the emerging computing paradigm (e.g., neuromorphic17,18 or quantum19,20 computing).

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