Coexistence of infrared plasmon and thermoelectricity in rare-earth semiconducting ytterbium nitride

Abstract

Rare-earth nitride (REN) pnictides are exciting materials due to their localized and strongly correlated 4f-electrons that lead to interesting magnetic properties useful for spintronic devices. Ytterbium nitride (YbN) is a unique rare-earth pnictide as it exhibits antiferromagnetic ground states, unlike most ferromagnetic RENs. Though the magnetic properties of YbN thin films have been studied before, the electronic, thermoelectric, and plasmonic properties of YbN are yet to be investigated. Here, we show coexisting high thermoelectric power factor and short-wavelength infrared plasmon polaritons in epitaxial YbN thin films deposited with the ultrahigh vacuum growth method. YbN thin films deposited on (001) MgO substrates exhibit epitaxial and good quality crystalline growth and exhibit a high thermoelectric power factor of ∼ 1.9 mW/mK2 at 750 K due to high electrical conductivity and a moderately high Seebeck coefficient. High carrier concentration also leads to a positive-to-negative dielectric permittivity transition in YbN at ∼1900–1950 nm, corresponding to the epsilon-near-zero plasmonic resonance. Low-temperature transport measurements revealed that dislocation and acoustic phonon scattering dominate electronic transport. Demonstration of coexisting high thermoelectric power factor and infrared plasmon polaritons marks important progress in designing YbN-based thermoelectric and plasmonic devices for future applications.