Cross-plane Thermoelectric and Thermionic Transport across Au/h-BN/Graphene Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Studying thermoelectric voltage at atomically abrupt interfaces is challenging due to a lack of suitable measurement tools.
• Atomically thin two-dimensional (2D) materials offer a promising platform for investigating interfacial thermoelectric transport.
• Understanding interfacial effects is crucial for developing next-generation electronic and energy devices.

Purpose of the Study:

• To develop and demonstrate a novel technique and device structure for probing thermoelectric transport across atomically abrupt interfaces.
• To investigate the thermoelectric properties of gold/hexagonal boron nitride/graphene (Au/h-BN/graphene) heterostructures.
• To explore thermoelectric and thermal transport at the nanometer length scale.

Main Methods:

• Fabrication of Au/h-BN/graphene heterostructures.
• Integration of an indium tin oxide (ITO) transparent electrical heater for in situ Raman spectroscopy and thermometry.
• Application of an AC voltage to the ITO heater and measurement of the thermoelectric voltage at 2ω using a lock-in amplifier.

Main Results:

• A novel technique for measuring interfacial thermoelectric voltage was successfully implemented.
• The Seebeck coefficient for the fabricated thermoelectric structure was determined to be -215 μV/K.
• The thermoelectric voltage generation at the graphene/h-BN interface was attributed to thermionic emission, not bulk diffusive transport.

Conclusions:

• The developed technique enables the study of thermoelectric transport at extremely short length scales.
• The observed Seebeck coefficient is an interfacial phenomenon, distinct from the bulk properties of the constituent materials.
• This work provides a new pathway for characterizing interfacial thermoelectric effects in 2D material-based heterostructures.