High-Temperature Thermoelectricity in LaNiO₃-La₂CuO₄ Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Transition metal oxides are crucial for electronics, energy storage, and conversion.
• Atomic layer-by-layer fabrication enables precise design of novel oxide materials.
• Understanding heterostructure properties is key to advanced functional materials.

Purpose of the Study:

• To investigate the thermoelectric properties of oxide heterostructures.
• To establish the relationship between heterostructure design and thermoelectric performance at high temperatures.
• To explore the impact of layer thickness and interface phenomena on transport properties.

Main Methods:

• Fabrication of oxide heterostructures using atomic layer-by-layer oxide molecular beam epitaxy.
• Utilized insulating lanthanum copper oxide (La₂CuO₄) and conductive lanthanum nickel oxide (LaNiO₃) layers.
• Characterized transport properties and employed high-resolution scanning transmission electron microscopy.

Main Results:

• Thermoelectric properties were found to be dependent on constituent layer thickness, interface intermixing, and oxygen dynamics.
• Reduced layer thickness led to decreased electrical conductivity and a change in the Seebeck coefficient's sign.
• Formation of a substitutional solid solution, La₂(CuNi)O₄, was observed at reduced layer thicknesses.

Conclusions:

• The study demonstrates tunable thermoelectric properties in La₂CuO₄/LaNiO₃ heterostructures.
• Layer thickness and interfacial effects significantly influence charge transport mechanisms.
• Atomic-scale engineering offers a pathway to optimize thermoelectric performance in transition metal oxides.