Thickness dependent chemical and microstructural properties of DC reactive magnetron sputtered titanium nitride thin films on low carbon steel cross-section

Polished samples of low carbon steel (LCS) rod cross-sections were sputtered with different thicknesses of TiNx thin film using DC reactive magnetron sputtering technique. While other process parameters such as target power (200 W), substrate position (150 mm) and sputtering pressure (1.33 Pa) were kept constant during the deposition, the deposition time was varied from 5 to 20 min. Physical and chemical characterizations of the samples were done using Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and optical microscopy. Vickers micro-hardness tester was used for the hardness test. The optimum value of the Vickers hardness was found to be 267.9 for the film deposited at 20 min. The inter-planar spacing was found to be from 2.0362 A to 2.0890 A, while corresponding lattice parameter was calculated to be from 4.0724 A to 4.1780 A. Scanning electron microscopy observation of the films gave an indication of fine-grained microstructure, which confirms the good adhesion and hardness properties of titanium nitride layer on the LCS substrate. The XRD spectra show that the multiphase reflections TiO2 (110) and TiN (111) for thinner film samples which shift to a preferred orientation (200) for thicker films, indicating a largely TiNx phase. This strongly suggest remarkable changes in crystal orientations of the TiNx films with deposition time. Ion beam (RBS) results showed increase in amount of nitrogen contents (47–64%) in TiNx films with thickness and deposition time.