Microstructure and Nanoindentation Hardness of Sputter Deposited Nanocrystalline Tantalum Thin Films

Tantalum (Ta) thin film was deposited onto Si (100) substrates using direct-current magnetron sputtering. The structure and mechanical properties of Ta films were investigated by X-ray diffraction, Field emission scanning electron microscope, and nanoindenter. The results indicated a transition from regular to irregular Hall-Petch relationship with decreasing grain size. Besides, a peak indentation hardness value of 12.8 GPa, much higher than that of bulk coarse-grained Ta, was obtained at the grain size of 36.3 nm.