Preparation and Research of Monolayer WS2 FETs Encapsulated by h-BN Material.

Tao Han,Shulong Wang,Shupeng Chen,Kun Yang,Hongxia Liu

doi:10.3390/mi12091006

Abstract

Functional devices that use vertical van der Waals (vdWs) heterostructure material can effectively combine the properties of single component materials, and the strong interlayer coupling effect can change their electronic and optical properties. According to our research, WS2/h-BN vertical vdWs heterostructure material can be synthesized by chemical vapor deposition (CVD) and wet transfer methods. Monolayer WS2 material and WS2/h-BN vertical vdWs heterostructure material can be tested and characterized using XPS, SEM, EDS, AFM and Raman spectroscopy, which can prove the existence of corresponding materials. When the thickness of the material decreases, the Coulomb scattering amongst two-dimensional (2D) layered materials increases. This is because both the shielding effect and the distance between the channel and the interface layer decrease. FET devices are then fabricated on WS2/h-BN vdWs heterostructure material by the electron beam lithography and evaporation processes. The effects of vdWs epitaxy on electrical transmission when WS2/h-BN vdWs heterostructure material is formed are explored. Finally, the related electrical performance of FET devices is tested and analyzed. Our experimental research provides guidance for the use of electronic devices with vdWs heterostructure material.

Highlights

Silicon-based transistors encounter short-channel effects and drain-induced barrier reduction problems as a device decreases in size [1,2]
As an excellent semiconductor material, WS2 /hexagonal boron nitride (h-BN) vertical van der Waals (vdWs) heterostructure material can be used for 2D ultra-thin electronics [10] and optoelectronic devices [11]
The element composition and valence state of WS2 material were analyzed by x-ray photoelectron spectroscopy (XPS), using the ESCALAB250 (Thermo Scientific Company, Waltham, MA, USA) instrument

Summary

Introduction

Silicon-based transistors encounter short-channel effects and drain-induced barrier reduction problems as a device decreases in size [1,2]. To overcome these problems, atomic thickness channel material is used to eliminate the potential adverse effects of device miniaturization. Monolayer WS2 and heterostructure materials are important for basic research and device applications, such as for photodetectors [4] and field effect transistors (FETs) [5]. The band gap of thin-layer hexagonal boron nitride (h-BN) material is 5.97 eV. There are no dangling bonds on the surface of h-BN material, which helps to decrease surface effects and electron scattering and improves mobility. As an excellent semiconductor material, WS2 /h-BN vertical vdWs heterostructure material can be used for 2D ultra-thin electronics [10] and optoelectronic devices [11]

Methods

Results

Conclusion