Investigating the optical response of titanium-nitride thin films after silver ion implantation and post-thermal annealing

The paper reports the study on dielectric functions of TiN films implanted with Ag ions and after annealing at 400 °C and 700 °C, employing spectroscopic ellipsometry technique. By using Drude-Lorentz modelling we have analysed and discussed in detail the evolution of screened and unscreened plasma frequency as well as Drude parameter. In comparison to as deposited film the real part of dielectric constant for Ag-implanted layers exhibits less negative values with increasing ion fluence implying the films possess less metallicity, whereas after annealing TiN becomes more metallic. Simultaneously, after implantation, the imaginary part is more than an order of magnitude lower than for the as deposited TiN and several times lower than that of Au and Ag. The magnitude of imaginary contribution of Ag-implanted TiN films decreases further after subsequent heat treatment at both 400 °C and 700 °C annealing temperatures. Although the differences in stoichiometry and microstructural changes, such as crystallite size, concentration of grain boundaries and defect density were assumed to be the major reason for the variation in optical properties of TiN, spectroscopic ellipsometry data exhibited much stronger effects than expected and indicated some other mechanisms could also be responsible for such behaviour.