Nanomechanical characterization of amorphous and nanocrystalline FeCuNbSiB thin films

Mechanical properties (hardness and Young's modulus) of amorphous and nanocrystalline Fe73.5Cu1Nb3Si15.5B7 thin films (thicknesses from 1.4 μm to 2 μm) have been investigated using the depth-sensing nanoindentation technique. The amorphous films, having uniform and smooth surfaces, were deposited on glass, aluminum, silicon, and sapphire substrates using the high power impulse magnetron sputtering technique. The nanocrystalline state was achieved after isothermal treatments performed at temperatures between 463 °C and 475 °C. The mean value for the effective Young's modulus of the amorphous Fe73.5Cu1Nb3Si15.5B7 thin films is about 146 GPa, regardless of their thickness or the substrate's nature. Increasing the thickness of the films, the hardness value increases up to 1 GPa. After the thermal treatments performed at 475 °C (when the films' structure consists of b.c.c. α-Fe(Si) grains with average size of 15 nm embedded in a residual amorphous matrix) the effective Young's modulus value decreases by about 13%, while hardness value increases by about 13% with respect to the as-deposited state.