Two-Dimensional Janus Antimony Selenium Telluride with Large Rashba Spin Splitting and High Electron Mobility

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

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 Nano2018121811-20), the concept can be extended to multifunctional two-dimensional (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 advance 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.

DFT investigation of the electronic and optical properties of hexagonal MX2/ZrXO (M = W, Mo and X = S, Se) van der Waals heterostructures for photovoltaic solar cell application

The van der Waals heterostructure of Janus materials with a TMD monolayer was used to create a two-dimensional class of nanomaterials for photovoltaic solar cell applications. It is one of the potential methods for enhancing the performance of photovoltaic systems. Two monolayers of different 2D materials, Janus (ZrXO) and TMDs (MX₂), are stacked together to form the heterojunction. Based on density functional theory structural, electrical, and optical properties were investigated. The favorable stacking and stability of the MX₂/ZrXO (M = W, Mo and X = S, Se) van der Waals heterostructures are confirmed through binding energies, phonon dispersion and ab initio molecular dynamics calculations. Standard excitonic peaks, which correspond to the bound valence-band hole and conduction-band electron, as well as excitonic peaks involving the mid-gap charges, can be seen in the system's computed absorption spectrum. MX₂/ZrXO van der Waals heterostructures are excellent photovoltaic candidates with a maximum achived power conversion efficiency of above 22%. Furthermore, we discovered that the heterostructure materials have a high absorption efficiency which is good for the intended photovoltaic solar cell application.