Emerging Group‐VI Elemental 2D Materials: Preparations, Properties, and Device Applications

Abstract

to micrometers or wafer scale. With different compositions and crystal structures, these 2D materials differ from each other in properties, offering wide range of material choices for diverse functionalities, including electronics, optoelectronics, sensors, energy conversion, and storage. [14-21] As Si transistors approach their scaling limit, the loss of gate electrostatic control on the nanoscale channel and the direct source-to-drain tunneling increase the off-state leakage currents, raise power dissipation, and thus severely degrade the performance of Si transistors. [22-25] Because of this scaling limit of Si transistors, exploration of new channel materials is of vital importance for future nanoelectronics. Due to the ultrathin thickness and dangling-bond-free surface, the emerging 2D materials are promising candidates for continuously downward scaling. [26] The diversity of 2D materials provides broad choices of semimetals (e.g., graphene), insulators (e.g., h-BN), and semiconductors (e.g., TMDs, BP, Se, Te). [8-13] The 2D semiconductors with thickness-dependent bandgaps have been regarded as potential channel materials for replacing Si. [26] The layered nature of 2D semiconductors allows consistent thickness control with atomic precision down to the monolayer limit, leading to enhanced electrostatic control of the gate and further scaling of transistors. Also, the pristine surfaces of 2D semiconductors are free of dangling bonds even down to monolayer limit. The pristine surfaces can give rise to low density of interface trap states and consequently reduce the charge scattering. Taking TMDs as an example, molybdenum disulfide (MoS 2), one of the most widely studied 2D semiconductors is a potential replacement for Si. [27-29] Based on theoretical calculation, 2D MoS 2 is predicted to have a direct source-to-drain tunneling leakage current two orders of magnitude smaller than that of Si. [22] For monolayer MoS 2 , the leakage current will not limit the scaling of transistors down to 1 nm gate length, which is superior to Si with a sub-5 nm scaling limit. [22] With the unique layer nature, 2D semiconductors alleviate the severe short channel effect. Therefore, 2D semiconductors have been regarded as potential options for transistors with ultimate thin channel. After realizing advantages of 2D semiconductors over Si, numerous research studies focus on searching for 2D semiconductors with high carrier mobility and an appropriate bandgap and exploring their usage in future nanoelectronics. Due to the ultrathin thickness and dangling-bond-free surface, 2D materials have been regarded as promising candidates for future nanoelectronics. In recent years, group-VI elemental 2D materials have been rediscovered and found superior in electrical properties (e.g., high carrier mobility, high photoconductivity, and thermoelectric response). The outstanding semiconducting properties of group-VI elemental 2D materials enable device applications including high-performance field-effect transistors and optoelectronic devices. ...

Bonding, structure, and mechanical stability of 2D materials: the predictive power of the periodic table

“…268 A comprehensive review treats the preparation methods, electrical properties, and device applications of group VI materials. 269…”

Bandgap prediction of two-dimensional materials using machine learning

“…Based on this motivation, it is anticipated that many theoretical and experimental studies have been conducted on their electronic properties [13][14][15]. Although the results of experimental studies are more reliable, it is difficult to carry out experiments on these thin materials owing to experimental constraints.…”

Adjusting the electronic properties and contact types of graphene/F-diamane-like C4F2 van der Waals heterostructure: a first principles study

“…14,15 Owing to their outstanding physical and chemical properties, 2D materials are promising candidates for electronics, optoelectronics and photocatalytics. [16][17][18] However, the aforementioned 2D materials have some disadvantages that hinder their application in many advanced technologies. For instance, the lack of a band gap in graphene limits its application in high-performance nanodevices like electronics and photoelectronics.…”