Zirconium nitride as a plasmonic material
: From thin films to multilayers

  • Sarah Ruddell

Student thesis: Doctoral ThesisDoctor of Philosophy


This PhD, having been sponsored and broadly defined by Seagate Technology, focuses on zirconium nitride(ZrN) as a potential alternative refractory plasmonic material for HAMR and other high temperature plasmonicapplications. This research also opens doors to other potential plasmonic applications for ZrN. The thermal stabilityof a ZrN/Cr90Ru10/SiO2 system is shown to be improved compared with Au, through demonstrations of an order ofmagnitude decrease in crystallite growth observed after thermal cycling. A high level of thermal stability isdemonstrated for the ZrN/Cr90Ru10/SiO2 system under vacuum conditions. A novel Ta2O5/Ta/ZrN/Cr90Ru10/SiO2passivation system suggests a reduction in ZrN oxidative thermal degradation in non-vacuum environments.

 Further tunability of the optical properties of ZrN is investigated with regards substrate, seed layer anddeposition temperature, showing that ZrN remains open to investigation as an alternative plasmonic material inthe IR spectral region for use within HAMR, through the demonstration of promising properties at 1550 nm on aproprietary Seagate Figure of Merit (FOM). A decrease in ZrN losses at wavelengths greater than ~900 nm issuggested for ZrN in the transdimensional regime. 

A reduction in ZrN losses is demonstrated on the inclusion of a HfN seed layer to ZrN growth on Si (100),MgO (100) and MgO (111) substrates, with highly textured growth of ZrN on MgO (100) and MgO (111) substratespresented. 

The research moves on from ZrN as a thin film, to its incorporation into multilayer systems, to investigatefurther tunability and application prospects. A novel ZrN/Mg1.8Zr0.2N2 multilayer system is experimentally realised,showing highly textured growth on MgO (100) and MgO (111) substrates.Effective medium approximation calculations of hyperbolic dispersion properties of the ZrN/Mg1.8Zr0.2N2system on MgO (100), whilst not conclusive due to modelling difficulties of the ultrathin constituent layers,demonstrates an exciting potential and outlook for this novel system.

Thesis embargoed until 31st July 2026
Date of AwardJul 2023
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsSeagate Technology LLC, Engineering & Physical Sciences Research Council & Royal Academy of Engineering
SupervisorRobert Bowman (Supervisor) & Robert Hadfield (Supervisor)


  • Plasmonics
  • Transition metal nitrides
  • heat assisted magnetic recording
  • Hyperbolic dispersion

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