Electrical, optical and mechanical properties of sputtered CrNy and Cr1−xSixN1.02 thin films

We have investigated the electrical, optical and mechanical properties of CrN y and Cr 1-x Si x N 1.02 films as a function of N and Si contents near the fcc-CrN stoichiometric composition. Polycrystalline CrN, with 0.93<y<1.15 and Cr 1-x Si x N 1.02 with 0<x< 0.16 were deposited by reactive magnetron sputtering. Optical reflectivity and electrical resistivity measurements indicate that the electronic properties of CrN y and Cr 1-x Si x N 1.02 thin films are strongly dependent on their chemical composition. The main changes in the optical properties of CrN y and Cr 1-x Si x N 1.02 films as a function of N or Si content mainly occur below 1.5 eV. Substoichiometric CrN y films with 0.93<y<0.98 exhibit room temperature resistivity ρ RT values of (1.2-7)×10 -3 Ω cm, metallic behavior and an antiferromagnetic orthorhombic phase transition at approximately 260K. In contrast, overstoichiometric CrN y (1.05<y<1.15) and Cr 1-x Si x N 1.02 films exhibit ρ RT values of (1.2-4)×10 -2 Ω cm and negative temperature coefficients of resistivity. Finally, the hardness values of CrN y films depend little on the chemical composition but are influenced by the film morphology: the nanohardness values of (111) CrN y are typically 12-14 GPa while (002) CrN y exhibit nanohardness values of 18 GPa. The addition of small amounts of Si increases the hardness values up to 22 GPa for Cr 0.94 Si 0.06 N 1.02 .