Diffusion Control on the Van der Waals Surface of Monolayers for Uniform Bi‐Layer MoS 2 Growth

In this work, the potential of 2D semi‐metallic PtSe2 as source/drain (S/D) contacts for 2D material field‐effect‐transistors (FETs) through theoretical and experimental investigations, is explored. From the density functional theory (DFT) calculations, semi‐metallic PtSe2 can inject electrons and holes into MoS2 and WSe2, respectively, indicating the feasibility of PtSe2 contacts for both n‐ and p‐metal‐oxide‐semiconductor FETs (n‐/p‐MOSFETs). Indeed, experimentally fabricated flake‐level MoS2 n‐MOSFETs and WSe2 p‐MOSFETs exhibit a significant reduction in contact resistance with semi‐metallic PtSe2 contacts compared to conventional Ti/Au contacts. To demonstrate the applicability for large‐area electronics, MoS2 n‐MOSFETs are fabricated with semi‐metallic PtSe2 contacts using chemical vapor deposition‐grown MoS2 and PtSe2 films. These devices exhibit outstanding performance metrics, including high on‐state current (≈10−7 A/µm) and large on/off ratio (>107). Furthermore, by employing these high‐performance MoS2 n‐MOSFETs, vertically stacked n‐MOS inverters are successfully demonstrated, suggesting that 3D integration of 2D material FETs is possible using semi‐metallic PtSe2 contacts.

Improvement of Contact Resistance and 3D Integration of 2D Material Field‐Effect Transistors Using Semi‐Metallic PtSe₂ Contacts

Seo,

Gyeon,

Seok

et al. 2024

Reducing Atomic Defects in 2D Transition Metal Dichalcogenides

Zhang,

Wang,

Nong

et al. 2024

Preparing high‐quality 2D semiconductors represented by transition metal dichalcogenides (TMDCs) is of great importance for the next‐generation devices. However, currently available 2D TMDCs contain many atomic defects, which greatly affect their electronic and optical properties. This review starts with the formation of atomic defects and their effects on the properties of 2D TMDCs. Then, techniques for characterizing atomic defects are systematically summarized, including atomic‐resolution imaging and spectroscopy measurements. Further, recent progress on defect suppression during growth and defect repair after growth is reviewed. Finally, challenges and opportunities in this important field are discussed.

Two‐Dimensional Layered Topological Semimetals for Advanced Electronics and Optoelectronics

Yu,

Zeng,

Zhang

et al. 2024

Due to the outstanding physical properties and the integrated characteristics, such as the gapless band structure, high state density, high conductivity, dangling‐bond‐free surface, and tunable Fermi level, two‐dimensional layered topological semimetals (2D LTSMs) exhibit a promising application prospect for including electrode contact and terahertz detection. Despite the surging in attention, a comprehensive strategy is still crucial to meet the necessary conditions for the practical application of 2D LTSMs. According to the fermion types and the band structures, 2D LTSMs can be divided into Dirac semimetals, Weyl semimetals, and nodal‐line semimetals. This review comprehensively encapsulates the intrinsic properties, typical synthesis methods, and applications in electronics and optoelectronics about these 2D LTSMs. To establish the fundamental theory, typical crystal structures, and physical properties of different 2D LTSMs are summarized at first. The effective synthesis strategies including exfoliation, molecular beam epitaxy, and vapor deposition are analyzed systematically. Finally, the article emphasizes the exploration of applications, significant challenges, and promising development directions of 2D LTSMs, which will drive 2D LTSMs to become the promisingly leading technology for next‐generation electronic and optoelectronic systems.