Aging time correlation in DC magnetron sputtered Ni60Ti40 thin films

In this work, Intermetallic NiTi thin films have been prepared using glancing angle DC magnetron sputtering technique on Si (1 0 0) substrate maintained at room temperature with separate elemental targets Ni and Ti. The films were solution treated (annealed) at 600 °C for 1 h followed by aging at 500 °C for 2 h, 4 h and 6 h. The degree of crystallinity increases with subsequent solution treatment followed by aging at different times. The hardness and elastic modulus increased from 8.32 to 9.41 GPa and from 148.92 to 163.13 GPa, respectively, with respect to the increase in aging time. From HR-XPS (High Resolution X-ray Photoelectron Spectroscopy) investigations, it was found that the films aged at different times have shown strong tendency to form thicker surface layer TiO2 (metal oxide) onto the film surface due to higher thermodynamic reactivity by leaving Ni-rich precipitates in the matrix immediately behind the metal oxide layer.