Vertical charge transport through transition metal dichalcogenides - a quantitative analysis

Area of Science:

• Materials Science and Engineering
• Condensed Matter Physics
• Nanotechnology

Background:

• Transition metal dichalcogenides (TMDs) are promising 2D materials for electronic devices.
• Understanding vertical transport is crucial for developing novel TMD-based architectures.
• Previous studies primarily focused on lateral transport in TMD transistors.

Purpose of the Study:

• To experimentally evaluate and theoretically analyze truly vertical transport in multi-layer TMD devices.
• To develop a comprehensive model for vertical transport across varying electric fields and temperatures.
• To determine key material parameters, including effective vertical transport mass and interface barrier heights.

Main Methods:

• Fabrication and characterization of 28 two-terminal devices using multi-layer MoS2 and WSe2.
• Systematic investigation of electric field and temperature dependence of vertical transport.
• Development of a transport model analogous to gate leakage current in amorphous dielectrics.

Main Results:

• A quantitative model describing vertical transport as Fowler-Nordheim mediated at high fields and thermal injection dominated at low fields was established.
• The effective vertical transport mass was extracted for the first time: m*/m0 (MoS2) ≈ 0.18 and m*/m0 (WSe2) ≈ 0.14.
• Metal contact-to-TMD interface barrier heights were confirmed to be comparable to those in lateral TMD transistors.

Conclusions:

• The developed model provides a robust framework for understanding vertical charge transport in TMDs.
• The extracted effective masses and confirmed interface barriers are critical parameters for designing future vertical TMD devices.
• This work advances the understanding of fundamental transport mechanisms in 2D materials for electronic applications.