Tailoring the optical response of mixed 2D transition metal carbide and nitride (MXenes) thin films

Two-dimensional MXenes have attracted significant interest for nanophotonic and optoelectronic applications due to their unique optical properties. However, tailoring these properties often requires iterative synthesis of MXenes with specific characteristics, such as electronic conductivity, absorption band position, and dielectric permittivity. Here, we present a simple and effective method to tune the dielectric permittivity of MXene thin films by mixing two distinct MXenes: optically metallic Ti₃C₂Tₓ and dielectric Nb₂CTₓ. By controlling the film composition, we achieve a shift of key spectral features. For example, the wavelength at which the optical properties of the film transition from dielectric to metallic, or epsilon near zero (ENZ) point, is continuously tailored over a broad spectral range from 1.1 to 2.6µm. This approach offers a straightforward and scalable alternative to conventional synthesis-based tuning methods, providing a versatile platform for engineering MXene-based optical materials.