Fabrication of plasmonic TiN nanostructures by nitridation of nanoimprinted TiO2 nanoparticles

Titanium nitride (TiN) is a new plasmonic material with advantages due to its greater thermal and chemical stability, compared to traditional metallic materials, i.e. gold and silver. TiN fabrication methods generally require reactive sputtering, which limits and complicates patterning capabilities. In this work, we demonstrate the fabrication of TiN films, as well as nano-patterned surfaces and three-dimensional (3D) structures by nitridation of crystalline titanium dioxide (TiO2) nanoparticle-based structures. TiO2 films are created by spin coating nanoparticle-based solutions, and TiO2 patterns are fabricated directly via solvent-assisted soft nanoimprint lithography. TiO2 films and structures were annealed in air and then reacted with ammonia gas at 1000 degrees C for 0, 2, 4, or 6 hours. SEM analysis shows that patterned TiO2 surfaces and 3D structures retain their structural integrity after treatment, allowing for a convenient method of fabricating patterned TiN nano-patterned surfaces and structures. Treated samples demonstrate the crystalline transition from tetragonal to cubic, which is consistent with the transition from anatase TiO2 to TiN. Additionally, using spectroscopic ellipsometry, we observe a change in the real permittivity from positive to negative. For 0 and 6 hour treatments, the real permittivity changes from 3.1 to -9.6 (at 1000 nm). TiN has potential use for many plasmonic and metamaterial applications. In this work, we demonstrate the excitation of surface plasmon polaritons (SPPs) via grating coupling using 1 mm-period TiN line gratings.