Argon irradiation effects on the structural and optical properties of reactively sputtered CrN films

The present study deals with CrN films irradiated at room temperature (RT) with 200 keV Ar+ ions. The CrN layers were deposited by d.c. reactive sputtering on Si (100) wafers, at nitrogen partial pressure of 5?10-4 mbar, to a total thickness of 280 nm. The substrates were held at 150?C during deposition. After deposition the CrN layers were irradiated with 200 keV Ar+ ions to the fluences of 5?1015 - 2?1016 ions/cm2. Structural characterization was performed with Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and X-ray diffraction (XRD). Spectroscopic ellipsometry measurements were carried out in order to study optical properties of the samples. The irradiations caused the microstructrual changes in CrN layers, but no amorphization even at the highest argon fluence of 2?1016 ions/cm2. Observed changes in microstructure were correlated with the variation in optical parameters. It was found that both refractive index and extinction coefficient are strongly dependent on the defect concentration in CrN layers.