Effect of the Si content on the microstructure of hard, multifunctional Hf-B-Si-C films prepared by pulsed magnetron sputtering

High-resolution TEM images showing that addition of 2 at% Si in the Hf-B-Si-C films results in a nanocolumnar structure (∼20-30 nm long and <5 nm wide) separated by ∼1 nm thick amorphous boundaries. The nanocolumns consist of HfB2 nanodomains (∼5 nm) grown along the [0 0 1] direction maintaining the high hardness of the film (∼37 GPa) while reducing the residual stresses.