TiN/dielectric nanolaminates: effects of metamaterial engineering and disorder on the superconductive properties

A series of TiN thin films and TiN/TiO ₂ and TiN/AlN nanolaminates were deposited using plasma-enhanced atomic layer deposition (PEALD) to study whether the previously demonstrated metamaterial approach to enhancing the superconductive properties of layered (i.e. hyperbolic meta-) materials is relevant to TiN. While none of the nanolaminate multilayers had superconducting transitions, T _c , that exceeded the bulk value of TiN, there were enhancements compared to the T _c ’s of very thin single layer films (thinner than 30 nm) of comparable thicknesses, which have reduced values due to the effects of disorder. Upon closer examination, it is apparent that the nanolaminate stacks do not behave like individual superconducting layers separated by dielectric layers, but rather as an anisotropic single layer which results in the higher T _c ’s than for single layer superconductors. This study demonstrates that the metamaterial engineering approach for hyperbolic superconductors results in a complex interplay between normal state resistivity and the enhancement of the attractive electron-electron interaction that is effective in enhancing their superconductive properties.