Novel Electronic and Magnetic Properties of Two‐Dimensional Transition Metal Carbides and Nitrides

TLDR

Layered MAX phases are exfoliated into 2D single layers and multilayers, so‑called MXenes. First‑principles calculations were used to study the formation and electronic properties of M₂C and M₂N MXenes with F, OH, and O surface functionalization. Sc₂C, Ti₂C, Zr₂C, and Hf₂C MXenes become semiconductors with suitable surface functionalization, while functionalized Cr₂C and Cr₂N MXenes are magnetic, and the resulting semiconducting MXenes show very large Seebeck coefficients at low temperatures.

Abstract

Abstract Layered MAX phases are exfoliated into 2D single layers and multilayers, so‐called MXenes. Using first‐principles calculations, the formation and electronic properties of various MXene systems, M 2 C (M = Sc, Ti, V, Cr, Zr, Nb, Ta) and M 2 N (M = Ti, Cr, Zr) with surfaces chemically functionalized by F, OH, and O groups, are examined. Upon appropriate surface functionalization, Sc 2 C, Ti 2 C, Zr 2 C, and Hf 2 C MXenes are expected to become semiconductors. It is also derived theoretically that functionalized Cr 2 C and Cr 2 N MXenes are magnetic. Thermoelectric calculations based on the Boltzmann theory imply that semiconducting MXenes attain very large Seebeck coefficients at low temperatures.