Anisotropic Carrier Mobility from 2H WSe₂.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• 2H phase Transition Metal Dichalcogenides (TMDCs) are crucial for next-generation electronics.
• Electrical anisotropy in TMDCs is essential for advanced devices like synaptic transistors and inverters in neuromorphic computing.
• Understanding and controlling electrical anisotropy is key to unlocking the full potential of TMDCs.

Purpose of the Study:

• To report and investigate the anisotropic carrier mobility in 2H tungsten diselenide (WSe2).
• To identify the underlying mechanism responsible for the observed electrical anisotropy.
• To explore the potential of this phenomenon for developing high-performance electronic devices.

Main Methods:

• Fabrication and characterization of WSe2 field-effect transistors.
• Measurement of anisotropic carrier mobility under varying gate voltages.
• Z-contrast scanning transmission electron microscopy (STEM) for structural analysis.
• Density Functional Theory (DFT) calculations to model electronic structures and scattering intensities.

Main Results:

• Anisotropic carrier mobility was observed in 2H WSe2 transistors, with an anisotropy degree ranging from 0.16 to 0.95.
• Phonon, impurity, and defect scattering mechanisms were ruled out as causes for the anisotropy.
• An intrinsic screening layer was identified as the source of electrical anisotropy.
• DFT calculations confirmed the role of seven types of intrinsic screening layers in modulating electronic properties and mobility.

Conclusions:

• The discovery of anisotropic carrier mobility in 2H WSe2 provides a new method to tune the physical properties of 2H TMDCs.
• This finding opens avenues for designing and integrating TMDC-based transistors with enhanced performance for neuromorphic computing.
• The intrinsic screening layer mechanism offers a pathway for precise control over electrical anisotropy in 2D materials.