Synthesis, characterisation, and spectral metrology of plasmonic titanium nitride films and nanostructures

Abstract

Plasmonics stands at the forefront of contemporary scientific research, rapidly advancing with the promise of fast and miniaturised devices. Traditional plasmonic materials like Gold and Silver are not suitable for a wide range of high-temperature and harsh environment applications due to their limitations in terms of thermal durability, chemical stability, and mechanical resilience. Alternative plasmonic materials have emerged as prominent candi- dates for pushing the boundaries of plasmonics. Among these materials, Titanium Nitride (TiN) has gained significant attention due to its remarkable attributes, including exceptional high-temperature stability, robust mechanical properties, chemical resilience, and noteworthy optical and plasmonic characteristics.

The primary objective of this research project is to unravel synthesis technique of plas- monic thin films and optimisation strategies, mainly for TiN thin films and associated nanostructures. The research has yielded valuable insights into the optical and plasmonic properties of TiN thin films, as showed through a rigorous analysis of factors like deposition temperature, nitrogen flow rates, and the incorporation of buffer layers. This work aims to bridge the gap between TiN’s exceptional material characteristics and its practical application in the realm of plasmonics.

The optical and plasmonic properties of TiN thin films have been greatly improved when using a Cr90Ru10 buffer layer on an amorphous fused silica substrate. This is observed by the reduction in both the real and imaginary parts of the dielectric permittivity of those thin films as well as a better plasmonic coupling efficiency via ATR, which is also confirmed using finite element simulations. This is thanks to the seeded growth of TiN on top of a Cr90Ru10 buffer layer, resulting in a highly textured TiN films in (200) direction. Further optimisation of TiN properties is done through the use of various substrates, seed layer, different nitrogen gas flows and deposition temperatures. This also proves that TiN is a highly tunable material in a visible and near-infra-red regions of the spectrum.

This research then progresses from properties of TiN thin films to the manufacture and metrology of the plasmonic nanostructures using EBL, DFS and CL. This study has given a valuable insights into the inner working of the plasmonic properties of the nanostructures made from previously characterised TiN thin films.

The ongoing dialogue in plasmonics is enriched by this work through the offering of a deeper understanding of TiN’s suitability for diverse applications. It introduces novel insights into the influence of deposition parameters on TiN thin film properties and delves into the nuanced behaviours of plasmonic nanostructures.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	EPSRC Centre for Doctoral Training in Photonic Integration and Advanced Data Storage
Supervisor	Robert Bowman (Supervisor) & Miryam Arredondo (Supervisor)