Spin-Current Modulation in Hexagonal Buckled ZnTe and CdTe Monolayers for Self-Powered Flexible-Piezo-Spintronic Devices

Abstract

The next-generation spintronic device demands the gated control of spin transport across the semiconducting channel through the replacement of the external gate voltage source by the piezo potential, as experimentally demonstrated in Zhu et al. ACS Nano, 2018, 12 (2), 1811−1820. Consequently, a high level of out-of-plane piezoelectricity together with a large Rashba spin splitting is sought after in semiconducting channel materials. Inspired by this experiment, a new hexagonal buckled two-dimensional (2D) semiconductor, ZnTe, and its iso-electronic partner, CdTe, are proposed herewith. These 2D materials show a strong spin-orbit coupling (SOC), which is evidenced by a large Rashba constant of 1.06 and 1.27 eV•Å, respectively, in ZnTe and CdTe monolayers. Moreover, these Rashba semiconductors exhibit a giant out-of-plane piezoelectric coefficient (d 33 ) = 88.68 and 172.61 pm/V, and can thereby generate a high piezo potential for gating purposes in spin field-effect transistors (spin-FETs). While the low elastic stiffness implies the mechanical flexibility or stretchability in these monolayers. The Rashba constants are found to be effectively modulated via external perturbations, such as strain and electric field. The wide band gap provides ample room for modulation in its electronic properties via external perturbations. Such scope is severely limited in previously reported narrow band gap Rashba semiconductors. The fascinating results found in this work indicate their great potential for applications in next-generation self-powered flexible-piezo-spintronic devices. Moreover, a new class of hexagonal buckled ZnX (X: S, Se, or Te) monolayers is proposed herein based on their previously synthesized bulk counterparts, while their electronic, mechanical, piezoelectric, and thermal properties have been thoroughly investigated using the state-of-art density functional theory (DFT).

Large piezoelectric response in ferroelectric/multiferroelectric metal oxyhalide MOX2 (M = Ti, V and X = F, Cl and Br) monolayers

“…Encouragingly, although 2D ferroelectrics are relatively rare to date, giant in-plane piezoelectric response is present in ferroelectric monolayers of group-IV monochalcogenides 19 and MXenes (e.g., Sc 2 CS 2 ) 20 . A huge out-of-plane piezo-response (d 33 = 172.61 pm/V) is observed in buckled monolayers 21 . Ferroelectric In 3 Se 3 nanoflakes 22 also show a moderate out-of-plane piezo-response.…”

“…20 A huge out-of-plane piezo-response ( d 33 = 172.61 pm V −1 ) is observed in buckled monolayers. 21 Ferroelectric In 3 Se 3 nanoflakes 22 also show a moderate out-of-plane piezo-response. Furthermore, the co-existence of piezoelectricity and magnetism and their coupling in 2D materials – namely vanadium dichalcogenide monolayers, 23 Janus ferromagnetic NiClI monolayers, 11 and 1H-LaBr 2 monolayers 24 – have been investigated.…”

Nanoampere‐Level Piezoelectric Energy Harvesting Performance of Lithography‐Free Centimeter‐Scale MoS2 Monolayer Film Generators

“…[ 9 ] Recently, piezoelectricity in the 2D material family with monolayer thickness has been extensively explored by theoretical calculations with the assumed strain in either in‐plane or out‐of‐plane direction, including transition‐metal‐based mono‐, di‐, and tri‐chalcogenides. [ 10–13 ] It was also experimentally demonstrated that the reduction of the number of atomic layers close to 1 nm thickness induced significant enhancements in piezoelectricity of 2D materials. [ 14–16 ] In particular, the actual performance of piezoelectric energy harvesters that exploit the piezoelectricity of monolayer structure has been reported.…”

Coupled Spin-Valley, Rashba Effect, and Hidden Spin Polarization in WSi2N4 Family

“…The discovery of graphene has enormously revolutionized the field of atomically thin two-dimensional (2D) materials because of its extraordinary electronic properties compared to the bulk counterparts. − Recent advancements in experimental techniques have explored many new 2D materials beyond graphene, including germanene, silicene, 2D boron nitride, , 2D transition metal dichalcogenides (TMDs), − and transition metal carbides/nitrides (MXenes). , The septuple atomic layer 2D materials MoSi 2 N 4 and WSi 2 N 4 have been experimentally synthesized by passivating the surfaces of nonlayered materials . These materials have a semiconducting nature with excellent ambient stability, high strength, and considerable carrier mobility.…”