High thermoelectricpower factor in graphene/hBN devices

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Nanoscal e cooling demands efficient passive and active methods.
• Graphene's high thermal conductivity aids passive cooling, but its low thermoelectric power factor limits active cooling.
• Previous active cooling strategies in graphene devices were constrained by substrate material limitations.

Purpose of the Study:

• To investigate the impact of hexagonal boron nitride (hBN) substrates on graphene's thermoelectric performance.
• To explore the potential for enhanced active cooling in graphene-based nanodevices.
• To demonstrate improved thermoelectric efficiency and gate-controlled switching capabilities.

Main Methods:

• Fabrication of graphene devices on hexagonal boron nitride (hBN) substrates.
• Characterization of thermoelectric properties, including the power factor and Seebeck coefficient.
• Analysis of substrate-induced potential fluctuations and their effect on device performance.

Main Results:

• Graphene devices on hBN substrates exhibited significantly improved thermoelectric performance compared to those on SiO₂.
• Room temperature efficiency (power factor times temperature) reached 10.35 W⋅m^-1⋅K^-1, surpassing existing bulk and 2D materials.
• Reduced potential fluctuations on hBN enabled fast gate-controlled switching of the Seebeck coefficient polarity.

Conclusions:

• Hexagonal boron nitride (hBN) is a superior substrate for enhancing graphene's thermoelectric properties.
• The improved performance enables practical applications in integrated active cooling devices.
• The Seebeck coefficient serves as a direct indicator of substrate-induced effects on thermoelectric performance.