Investigation of localized surface plasmon resonance of TiN nanoparticles in TiN_xO_y thin films

Abstract

Titanium oxynitride (TiNxOy) thin films are deposited by RF sputtering with various N2 flow rates. Two distinct absorption bands, one in the photon energies of ~0.5 – 2.5 eV and the other in the energies of ~3.5 – 5 eV, which correspond to the localized surface plasmon resonance (LSPR) of the TiN nanoparticles in the thin films and the interband transitions in TiNxOy, respectively, are observed in the absorption measurement. A Drude-Lorentz model, including the contributions of the free electrons, LSPR and interband transitions, is able to well fit the spectroscopic ellipsometric (SE) data. The resonance energy and strength of the LSPR oscillator are accurately determined from the SE analysis. The resonance energy is in the range of ~1 – 1.3 eV and blue-shifts with increasing N2 flow rate; and the strength decreases significantly with increasing N2 flow rate. The plasma energy yielded from the SE analysis shows a correlation with the conduction electron concentration obtained from the Hall effect measurement. It is shown that the LSPR plays a significant role in the complex dielectric function of the TiNxOy grains at the low photon energies (~0.5 – 1.5 eV).