Band Alignment in WSe2-Graphene Heterostructures.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Understanding the electronic properties of 2D materials like graphene and transition metal dichalcogenides (TMDs) is crucial for advanced electronic devices.
• Accurate determination of band alignment and dielectric properties in heterostructures is essential for device design and performance prediction.

Purpose of the Study:

• To experimentally determine the band offset between the graphene neutrality point and the WSe2 conduction and valence band edges.
• To measure the WSe2 dielectric constant along the c-axis using graphene-based heterostructures.

Main Methods:

• Fabrication and characterization of two types of heterostructures: WSe2-on-graphene and graphene-on-WSe2.
• Utilizing dual-gated graphene field-effect transistors with WSe2 as a top dielectric to measure WSe2 capacitance and dielectric constant.
• Analyzing lateral electron transport in graphene-on-WSe2 heterostructures to observe ambipolar behavior and conductivity saturation.

Main Results:

• The WSe2 dielectric constant along the c-axis was determined as a function of thickness.
• Ambipolar transport in graphene was observed alongside conductivity saturation in WSe2 due to carrier population in its conduction and valence bands.
• The band offsets between graphene and WSe2 were precisely quantified by combining data from both heterostructure configurations.

Conclusions:

• The study successfully established a quantitative understanding of the electronic band alignment in graphene-WSe2 heterostructures.
• The determined dielectric properties of WSe2 are vital for optimizing its use in electronic and optoelectronic applications.
• These findings provide critical parameters for the rational design of novel van der Waals heterostructure devices.