Epitaxial superlattices with titanium nitride as a plasmonic component for optical hyperbolic metamaterials

Gururaj V. Naik, Purdue University, Birck Nanotechnology Center
Bivas Saha, Purdue University, Birck Nanotechnology Center
Jing Liu, Purdue University
Sammy M. Saber, Purdue University, Birck Nanotechnology Center
Eric A. Stach, Purdue University, Birck Nanotechnology Center
Joseph Irudayaraj, Purdue University, Bindley Bioscience Center
Timothy D. Sands, Purdue University, Birck Nanotechnology Center
Vladimir M. Shalaev, Purdue University, Birck Nanotechnology Center
Alexandra Boltasseva, Purdue University, Birck Nanotechnology Center

Abstract

Titanium nitride (TiN) is a plasmonic material having optical properties resembling gold. Unlike gold, however, TiN is complementary metal oxide semiconductor-compatible, mechanically strong, and thermally stable at higher temperatures. Additionally, TiN exhibits low-index surfaces with surface energies that are lower than those of the noble metals which facilitates the growth of smooth, ultrathin crystalline films. Such films are crucial in constructing low-loss, high-performance plasmonic and metamaterial devices including hyperbolic metamaterials (HMMs). HMMs have been shown to exhibit exotic optical properties, including extremely high broad-band photonic densities of states (PDOS), which are useful in quantum plasmonic applications. However, the extent to which the exotic properties of HMMs can be realized has been seriously limited by fabrication constraints and material properties. Here, we address these issues by realizing an epitaxial superlattice as an HMM. The superlattice consists of ultrasmooth layers as thin as 5 nm and exhibits sharp interfaces which are essential for high-quality HMM devices. Our study reveals that such a TiN-based superlattice HMM provides a higher PDOS enhancement than goldor silver-based HMMs.

Discipline(s)

Nanoscience and Nanotechnology