Robust plasmonic properties of epitaxial TiN films on highly lattice-mismatched complex oxides

High-quality titanium nitride (TiN) film is a prominent plasmonic material in the fields of plasmonics and nanophotonics, which is usually synthesized on several limited substrates (such as MgO, silicon, and sapphire). With the rapid development of hybrid optoelectronic devices composed of plasmonic materials and functional oxides, it is promising to integrate high-quality TiN films with a variety of functional oxides, which requires to accommodate TiN films to a broad spectrum of lattice mismatch. In this work, we synthesized high-quality single-crystalline TiN films on various oxide substrates [MgO, MgAl2O4, (LaAlO3)(0.30)-(SrAl1/2Ta1/2O3)(0.70), and YAlO3] by high-pressure magnetron sputtering. It is surprising that the epitaxial TiN films can accommodate extremely large lattice mismatch up to -15.39%. The crystal and electronic structures of the TiN films were characterized by high-resolution x-ray diffraction, atomic force microscopy, and x-ray photoemission spectroscopy measurements. The optical and electrical properties of the TiN films on various oxide substrates were investigated by spectroscopic ellipsometry and Hall effect measurements. It is revealed that the remarkable optical properties of TiN films are robust even on highly lattice-mismatched oxide substrates. Our work paves a way to integrate plasmonic TiN films with a variety of functional oxides for high-performance hybrid optoelectronic devices.