Insights into selected 2D piezo Rashba semiconductors for self-powered flexible piezo spintronics: material to contact properties

Abstract

The new paradigm in electronics consists in realizing the seamless integration of many properties latent in nanomaterials, such as mechanical flexibility, strong spin-orbit coupling (Rashba spin splitting - RSS), and piezoelectricity. Taking cues from the pointers given on 1D ZnO nanowires [ACS Nano 2018, 12, 1811−1820], the concept can be extended to multifunctional 2D materials, which can serve as an ideal platform in next-generation electronics such as self-powered flexible piezo-spintronic device. However, a microscopically clear understanding reachable from the state-of-the-art density functional theory-based approaches is a prerequisite to advancing this research domain. Atomic-scale insights gained from meticulously performed scientific computations can firmly anchor the growth of this important research field, and that is of undeniable relevance from scientific and technological outlooks. This article reviews the scientific progress in understanding 2D materials hosting all the essential properties, i.e., flexibility, piezoelectricity, and RSS. Important 2D semiconducting monolayers that deserve a special mention, include monolayers of buckled MgX (X=S, Se, Te), CdTe, ZnTe, Janus structures of transition metal trichalcogenides, Janus tellurene and 2D perovskites. van der Waals multilayers are also built to design multifunctional materials via modulation of the stacking sequence and interlayer coupling between the constituent layers. External electric field, strain engineering and charge doping are perturbations mainly used to tune the spintronic properties. Finally, the contact properties of these monolayers are also crucial for their actual implementation in electronic devices. The nature of the contacts, Schottky/Ohmic, needs to be carefully examined first as it controls the device's performance. In this regard, the rare occurrence of Ohmic contact in graphene/MgS van der Waals hetero bilayer has been presented in this review article.

Unravelling the band splitting origin in bulk and 2D distorted α-CsPbI3 perovskite

“…flexibility, piezoelectricity, and Rashba spin splitting. 12 Katan and coworkers have investigated theoretically metal substitution based on available crystallographic data of tri-chloride CH 3 NH 3 MCL 3 (M = Pb, Sn, Ge) crystal structures, having a 3D inorganic network of corner-shared octahedra. 13 Furthermore, an investigation of bromide and iodide revealed that spin–orbit interaction stemming from halogens might also be significant, especially for iodide.…”

Novel Piezoelectricity in Two-Dimensional Metallic/Semimetallic Materials with Out-of-Plane Polarization

“…The piezoelectric effect reflects the change of electric polarization with an external strain. Materials with piezoelectric effect have useful application prospects, such as sensors, − transistors, energy harvesting systems, − medical imagining, photocatalysts, , optoelectronics, , valleytronics, and self-powered piezo spintronics. , Since graphene, a single atomic layer of carbon, was successfully prepared in 2004, two-dimensional (2D) materials have attracted great interest due to their unique properties . The experimental detection of the piezoelectric effect of MoS 2 monolayer semiconductor material makes the 2D material with piezoelectric effect move from theory to reality. ,, Subsequently, the entrance of 2D piezotronics was opened.…”

“…21 Fifth, it can be combined with the Rashba effect. 11,22,23 For example, CrSSe and CrSeTe monolayer are materials with both Rashba spin splitting and piezoelectricity, which may become efficient micronano spintronics. 22 Graphene and many other 2D materials (such as silicene and germanene, 24,25 graphynes, 26 borophene, 27,28 FeB 2 monolayer, 29 t-BN, 30 and M 3 X 2 31 ) constitute a special class of 2D materials called Dirac materials due to their characteristic cone-like band structure near the Fermi level, and the resulting low-energy excitations behave as massless Dirac fermions, 14,32,33 which further leads to various novel phenomena and properties such as fractional quantum Hall effect 34,35 and ultrahigh carrier mobility.…”

“…clamped 0 0 (11) where Q 0 , h 0 , and S 0 are the quantities without strain, and k 0 and k 1 are introduced parameters (k 0 ≡ 1 for in-plane uniaxial strain). It is noted that h does not change when the ions are clamped.…”

“…Fourth, it can be combined with flexoelectricity; e.g., the piezoelectricity of semiconducting 2H-MoTe 2 can be turned by surface corrugation-mediated flexoelectricity . Fifth, it can be combined with the Rashba effect. ,, For example, CrSSe and CrSeTe monolayer are materials with both Rashba spin splitting and piezoelectricity, which may become efficient micronano spintronics …”