Growth of multiple WS2/SnS layered semiconductor heterojunctions

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) van der Waals semiconductors like WS2 and SnS offer unique electronic properties.
• WS2 exhibits n-type behavior, while SnS demonstrates p-type conductivity.
• Heterostructures combining different 2D materials are crucial for novel electronic devices.

Purpose of the Study:

• To investigate the heteroepitaxy of WS2 and SnS 2D materials.
• To characterize the electronic properties of WS2/SnS heterostructures.
• To understand the factors influencing charge carrier mobility in these heterostructures.

Main Methods:

• Atomic layer deposition (ALD) was used to grow alternating WS2 and SnS layers on 5 cm × 5 cm substrates.
• Fabrication and characterization of back-gated transistors for individual WS2 and SnS films.
• Electrical transport measurements at room temperature to determine carrier mobility.
• Transmission electron microscopy (TEM) to analyze the crystallographic orientation and interface structure.

Main Results:

• Individual WS2 transistors showed n-type behavior with a mobility of 12 cm²/V·s.
• Individual SnS transistors exhibited p-type conductivity with a high hole mobility of 818 cm²/V·s.
• The WS2/SnS heterostructure displayed ambipolar behavior, with electron mobility slightly enhanced compared to pure WS2.
• A significant reduction in hole mobility was observed in the heterostructure.

Conclusions:

• The heteroepitaxy of WS2 and SnS was successfully achieved using ALD.
• The observed ambipolar behavior in the heterostructure is consistent with the combination of n-type WS2 and p-type SnS.
• The substantial decrease in hole mobility is attributed to the perpendicular striation direction and 15-degree twist between WS2 and SnS layers, creating significant scattering at van der Waals interfaces.