Macroscopic and microstructural properties of CSixNy thin films deposited by RF nitrogen-plasma-assisted pulsed laser deposition

Carbon silicon nitride (CSixNy) thin films have been grown by pulsed laser deposition (PLD) of various [C(1−z)(Si3N4)z]-targets using an additional nitrogen RF plasma source on [1 0 0] oriented silicon substrates without additional heating. At the beginning of the deposition the resulting microstructure is amorphous with some embedded microcrystals of ≈30 nm diameter, which induce increasing internal stress. After less than 200 nm thickness the growth of the films is changing, resulting in an amorphous microstructure with textured nanocrystallites. In this growth-mode the internal stress is decreasing. Due to the resulting low internal stress, CSixNy films can be grown to a thickness above 3 μm, in contrast to DLC films. The microstructure of the films is found as textured graphitic planes of small size connected to each other by fullerene-like three-dimensional CNx-structures. This three-dimensional bonding network leads to high nanohardness of up to 20 GPa. Most of the silicon is bonded to carbon, which results in anisotropic hardness properties.