Polycrystalline titaniumnitride (TiN) layers of 240 nmthickness and columnar microstructure were deposited at 150 degrees C by d. c. reactive sputtering on Si(100) wafers and then irradiated at roomtemperature with either 80 keV V+ ions (at fluences of up to 2x10(17) ions/cm(2)) or 200 keV Ar+ ions (at fluences of 5x10(15)-2x10(16) ions/cm(2)). Rutherford backscattering spectroscopy, cross-sectional (high-resolution) transmission electron microscopy and X-ray diffraction were used to characterize ion-induced changes in the structural properties of the films. Their optical and electric properties were analyzed by infrared reflectance (IR) and electric resistivity measurements. After deposition, the stoichiometric TiN films had a (111) texture. Ion implantation generated a damaged surface layer of nanocrystalline structure, which extended beyond the implantation profile, but left an undamaged bottom zone of (111) orientation. This layer geometry determined from transmission electron microscopy was inferred in the analysis of IR reflectance data using the Drude model, and the variation of the electric and optical resistivity with the irradiation was deduced. The results were compared to those recently gained for ion-implanted reactively sputtered chromium nitride films. (C) 2013 Elsevier B.V. All rights reserved.