Structural and Optical Properties of Transition Metal Nitride Thin Films Deposited by Magnetron Sputtering

Transition metal nitride (TMN) thin films such as zirconium nitride provide high stability while possessing similar plasmonic properties to traditionally utilized plasmonic materials Au and Ag. Studying the synthesis of nanostructured TMN thin films is of importance for the widespread adoption of plasmonic devices.  Zirconium nitride thin films were deposited on an array of dewetted Au nanoparticles by reactive RF magnetron sputtering in a chamber of Ar and N₂. DC magnetron sputtering at a glancing angle was utilized to deposit aluminum nitride thin films. Zirconium nitride films sputtered at 125 W of power with 2 mTorr of N­₂ and 10 mTorr of Ar were shown to posses high crystallinity and a preferred (111) orientation. Optical spectroscopy indicated Au nanoparticle samples coated with zirconium nitride exhibited larger than 150nm redshifted plasmon resonances. The transmission spectra also suggest that zirconium nitride coatings broaden the plasmon resonance. Glancing angle deposition along with substrate rotation during aluminum nitride synthesis resulted on a zigzagged film structure. Cross-sectional field emission scanning electron microscopy indicated highly columnar growth of the aluminum nitride zigzags. Zirconium nitride coated Au nanoparticle films were used to tune the plasmonic properties of Au and could be useful in near infrared plasmonics. Glancing angle deposition of aluminum nitride offers a pathway to chiral transition metal nitride plasmonic films.