Tunable Electronic Properties of Type-II SiS2/WSe2 Hetero-Bilayers

High out-of-plane negative Poisson's ratios and strong light harvesting in two-dimensional SiS2 and its derivatives

Two-dimensional (2D) materials with negative Poisson's ratios (NPRs) hold tremendous potential in diverse electronic devices. However, most 2D auxetic materials exhibit small out-of-plane NPRs and materials with bi-directional NPRs are rare. In this work, the SiS2 monolayer and its derivatives MX2 (M = Si, Ge, Sn and X = S, Se, Te) are systematically studied via first-principles simulation. We demonstrate that a SiS2 monolayer possesses a remarkable out-of-plane NPR with a value of -1.09 and an in-plane NPR (-0.13). Furthermore, a higher out-of-plane NPR (-1.79) can be achieved in a SnS2 monolayer by element substitution. Remarkably, SiS2 and its derivative MX2 monolayers exhibit excellent light harvesting over the ultraviolet and visible range, and the corresponding electronic properties show robustness against strains. Our results confirm that MX2 monolayers provide an ideal platform to explore auxeticity in two-dimensional limits.

Emerging Trends in 2D TMDs Photodetectors and Piezo-Phototronic Devices

The piezo-phototronic effect shows promise with regards to improving the performance of 2D semiconductor-based flexible optoelectronics, which will potentially open up new opportunities in the electronics field. Mechanical exfoliation and chemical vapor deposition (CVD) influence the piezo-phototronic effect on a transparent, ultrasensitive, and flexible van der Waals (vdW) heterostructure, which allows the use of intrinsic semiconductors, such as 2D transition metal dichalcogenides (TMD). The latest and most promising 2D TMD-based photodetectors and piezo-phototronic devices are discussed in this review article. As a result, it is possible to make flexible piezo-phototronic photodetectors, self-powered sensors, and higher strain tolerance wearable and implantable electronics for health monitoring and generation of piezoelectricity using just a single semiconductor or vdW heterostructures of various nanomaterials. A comparison is also made between the functionality and distinctive properties of 2D flexible electronic devices with a range of applications made from 2D TMDs materials. The current state of the research about 2D TMDs can be applied in a variety of ways in order to aid in the development of new types of nanoscale optoelectronic devices. Last, it summarizes the problems that are currently being faced, along with potential solutions and future prospects.