Controlling the plasmonic properties of ultrathin TiN films at the atomic level

TL;DR

This study combines theoretical and experimental methods to analyze and control the plasmonic properties of ultrathin TiN films at the atomic level, revealing persistent metallic behavior and tunable plasmonic features.

Contribution

It provides new insights into the atomic-scale control of TiN film plasmonics, including effects of thickness, oxidation, and strain, enabling tailored optical properties for advanced applications.

Findings

Ultrathin TiN films retain metallic character.

Plasmon energy shifts to lower values as thickness decreases.

Surface oxidation and substrate strain influence optical properties.

Abstract

By combining first principles theoretical calculations and experimental optical and structural characterization such as spectroscopic ellipsometry, X-ray spectroscopy, and electron microscopy, we study the dielectric permittivity and plasmonic properties of ultrathin TiN films at an atomistic level. Our results indicate a remarkably persistent metallic character of ultrathin TiN films and a progressive red shift of the plasmon energy as the thickness of the film is reduced. The microscopic origin of this trend is interpreted in terms of the characteristic two-band electronic structure of the system. Surface oxidation and substrate strain are also investigated to explain the deviation of the optical properties from the ideal case. This paves the way to the realization of ultrathin TiN films with tailorable and tunable plasmonic properties in the visible range for applications in ultrathin metasurfaces and flexible optoelectronic devices.