Field-effect at electrical contacts to two-dimensional materials

Abstract

The inferior electrical contact to two-dimensional (2D) materials is a critical challenge for their application in post-silicon very large-scale integrated circuits. Electrical contacts were generally related to their resistive effect, quantified as contact resistance. With a systematic investigation, this work demonstrates a capacitive metal-insulator-semiconductor (MIS) field-effect at the electrical contacts to 2D materials: The field-effect depletes or accumulates charge carriers, redistributes the voltage potential, and gives rise to abnormal current saturation and nonlinearity. On one hand, the current saturation hinders the devices’ driving ability, which can be eliminated with carefully engineered contact configurations. On the other hand, by introducing the nonlinearity to monolithic analog artificial neural network circuits, the circuits’ perception ability can be significantly enhanced, as evidenced using a coronavirus disease 2019 (COVID-19) critical illness prediction model. This work provides a comprehension of the field-effect at the electrical contacts to 2D materials, which is fundamental to the design, simulation, and fabrication of electronics based on 2D materials. Electronic Supplementary Material Supplementary material (results of the simulation and SEM) is available in the online version of this article at 10.1007/s12274-021-3670-y.

Asymmetric electrode geometry induced photovoltaic behavior for self-powered organic artificial synapses

“…Under UV illumination, electron-hole pairs generate in the channel, and then separate into free electrons and holes. Electrons are captured at the C 8 -BTBT/PMMA interface, while the holes tend to diffuse to the Au/C 8 -BTBT interface towards contact on both sides due to the photogenerated carrier concentration gradient in the channel induced by the asymmetric contact areas and the effective capacitive coupling between the metal sidewall and the sufficiently short channel (∼6 µm) [45]. Thus, the Schottky barriers on both sides of the Au/C 8 -BTBT interface are substantially reduced, leading to an increase in the channel conductivity [46][47][48][49].…”

Sub-9 nm high-performance and low-power transistors based on an in-plane NbSe2/MoSe2/NbSe2 heterojunction

“…Due to their atomic-scale thickness and flat surface without any dangling bonds, two-dimensional (2D) semiconductor materials are distinguished from alternative channel materials by their well-controlled gate and effective carrier transport capabilities. [6][7][8][9] Recently, research into two-dimensional semiconductor material FETs has attracted widespread interest. [10][11][12][13] Since the first successful exfoliation of graphene, 14 2D semiconducting materials have proliferated, both through theoretical prediction and experimental synthesis.…”

“…Due to their atomic-scale thickness and flat surface without any dangling bonds, two-dimensional (2D) semiconductor materials are distinguished from alternative channel materials by their well-controlled gate and effective carrier transport capabilities. 6–9 Recently, research into two-dimensional semiconductor material FETs has attracted widespread interest. 10–13…”

Contact Properties of Two-Dimensional Ferroelectric α-In2Se3

“…Besides the work function of the metal and the Fermi level of the semiconductor, the preparation method and thickness of the 2D material, the preparation methods of the contact, the contact configuration, and annealing processes could also change the contact property. 27,28 Fermi-level pinning (FLP) has been observed in some 2D materials, such as MoS 2 29 and WSe 2 . 30 It is still unknown whether FLP also exists in α-In 2 Se 3 .…”

“…However, the Pd-contact device prepared by electron beam deposition has demonstrated to form an Ohmic contact with exfoliated α-In 2 Se 3 but forms a Schottky barrier with multilayer α-In 2 Se 3 grown by vapor-phase deposition (VPD). , Many factors can influence the contact properties between metals and semiconductors. Besides the work function of the metal and the Fermi level of the semiconductor, the preparation method and thickness of the 2D material, the preparation methods of the contact, the contact configuration, and annealing processes could also change the contact property. , Fermi-level pinning (FLP) has been observed in some 2D materials, such as MoS 2 and WSe 2 . It is still unknown whether FLP also exists in α-In 2 Se 3 .…”