Mechanical Properties and Microstructural Evolution of Ta/TaNx Double Layer Thin Films Deposited by Magnetron Sputtering

Crystalline tantalum thin films of about 500nm thickness were deposited on AISI 316L stainless steel substrate using magnetron sputtering. To investigate the nano-mechanical properties of tantalum films, deposition was performed at two temperatures (25°C and 200°C) on TaNx intermediate layer with different N2/Ar flow rate ratio from 0 to 30%. Nano-indentation was performed to obtain the mechanical properties of the films including hardness, Young’s modulus and plasticity free of substrate influence. Cross sectional FESEM was performed to measure the thickness of films. To evaluate the results, the grain size and crystallographic structure of the films was obtained, using atomic force microscopy (AFM) and X-Ray diffraction (XRD) respectively. It was found that, increasing sputtering temperature up to 200°C leads to slight decrease in hardness and Young’s modulus, and small increase in plasticity due to grain growth without any phase transformation. Whereas, using TaNx interlayer promoted formation of cubic-tantalum with higher plasticity and lower hardness in comparison to tetragonal structure, so it can makes tantalum film an applicable product for mechanically protecting.