Research Progress

Van der Waals Epitaxial Trilayer MoS2 Crystals for High-Speed Electronics

author: time:2022-09-08 clicks:

Fig1. (a) Schematic of bottom-gated trilayer MoSFETs with Ni/Au contacts. (b) SEM images of the trilayer MoSdevice. The scale bar is 2 µm. The contact bars with a length of 2 μm were defined by e-beam lithography. The right panel shows the zoom-in image of the trilayer MoStransistor with a channel length of 40 nm. The scale bar is 100 nm. (c) Cross-sectional high-resolution TEM images of the 40 nm MoSFET region. The scale bar is 20 nm. The left panel shows the zoom-in image of the trilayer MoScontact region. The scale bar is 2 nm. (d) Transfer characteristics of the 40 nm MoStransistor at room temperature. (e) Output characteristics of the 40 nm MoStransistor at room temperature. (f) Output characteristics of the same device at 4.3 K.


In the past few years, two-dimensional (2D) molybdenum disulfide (MoS2) hasattracted tremendous research attentiondue to its atomically thin layered structure and high carrier mobility.These features make MoSespecially interesting as a promising candidate for many applications. Importantly, it is believed to beimmune against short-channel effects because of the ultrathin body channel.However, the overall performance of short-channel MoSFETs based on CVD monolayer MoSin previous studies is still substantially lower than those of conventional Si FETs at the same channel length. One of the main limiting factors is the physical damage of the monolayer crystal during metal deposition, leading to a substantial contact resistance Rc, which becomes the bottleneck for device performance, especially in short channel devices. Moreover, saturation velocity vsat, instead of mobility, is critical to determine the on-state current for short-channel transistors and is still largely lacking. It also limits the intrinsic frequency of a transistor based on fTvsat/(2πLch).Here, we successfully demonstrate the epitaxy growth of trilayer MoSsingle crystals on soda-lime glass substrates and high-performance short channel trilayer MoSFETs.

What is discovered?

we have grown large domain and high mobility trilayer MoScrystalson soda-lime glass substrates by a scalable CVD approach. Spectroscopic characterizations reveal a weak interface interaction between MoSand soda-lime glass. Clear and sharp atomic-resolution STEM imaging determines the ABB stacking sequences in CVD-grown trilayer MoS2. The short-channel MoStransistors with ultrathin HfLaO dielectrics exhibit a high drain current (589 μA/μm atVds= 1 V) as well as record-high saturation velocity (4.2´10cm/s) at room temperature, which increases further at 4.3 K. The excellent electrical properties of the trilayer channelenablereduced surface scattering and lower contact resistance compared with the monolayer channel counterpart, making it a promising 2D material for future electronics applications.

What is important?

Trilayer MoS2, with high mobility and higher density of states, has attracted great interest recently, withextensive studies oncontrollable high-quality growth methods. Although considerable efforts have been devoted to growing trilayer MoSfilms on SiOor sapphire substrates, they commonly suffer from extensive domain/grain boundaries,substrate-induced defects, and small domain size, as well as inferior electrical properties compared with exfoliated ones. The growth of trilayer MoSon soda-lime glass substrates is stillunderdeveloped.

Why did we need WHMFC?

Micro/Nano Fabrication Platform provides sufficient cleanrooms of high level cleanness, in which micro-nano scale materials and devices may be fabricated and tested. High end facilities includes: vacuum sputtering coating system, light lithography system、etching system, etc., which will support for high quality fabrication and characterization of complex quantum electric circuits.

Who did the research?

Xuefei Li1,*, Zhenfeng Zhang1, Tingting Gao1, Xinhang Shi1, Chengru Gu1, and Yanqing Wu1,2,*

1Wuhan National High Magnetic Field Center and School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

2School of Integrated Circuits, Peking University, Beijing 100871

*Corresponding authors:;


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