Mechanical studies of thermally annealed nc-W2N embedded a-Si3N4 nanocomposite films

- The nc-W2N/a-Si3N4 films were grown by reactive magnetron co-sputtering.
- Dominant polycrystalline cubic phase of W2N is formed.
- Larger grain reduces to smaller grains in columnar structure when heated at high temperature.
- Hardness and other mechanical properties of nc-W2N/a-Si3N4 film enhanced upon annealing.
- Hardness of films reaches ~ 34 GPa at 700 °C annealing.

Nanocrystalline tungsten nitride (nc-W2N) embedded amorphous silicon nitride (a-Si3N4) nanocomposite films (nc-W2N/a-Si3N4) were grown by reactive magnetron sputtering. The films were prepared at 300 °C substrate temperature on Si (100) substrate. The as-prepared films were annealed at 500 °C and 700 °C in a high vacuum furnace for 30 min. Grazing incidence X-ray diffraction (GIXRD) results showed the formation of a polycrystalline cubic phase of W2N in as-prepared, 500 °C and 700 °C annealed films. Whereas with an increase in annealing temperature, GIXRD peaks shift towards higher angle and preferred orientation along (220) plane was also observed. The average crystallite size of as prepared film was 20.7 ± 4.5 nm then it reduced to 9.3 ± 3.4 nm and 7.6 ± 2.1 nm at 500 °C and 700 °C annealing temperature respectively. Field Emission Scanning Electron Microscopy micrograph showed irregular and well-developed grains on the surface of as prepared film. The reduced grain arrangement was observed in annealed films. The elongated columnar structure of as prepared film leads to diffused structure at higher annealing temperature. Energy dispersive X-ray spectroscopy confirms the presence of W, Si and N elements in the films. Hardness (H), elastic modulus (E) and elastic recovery (We) of the film improves with rise in annealing temperature. The highest H, E and We achieved were 39.3 ± 1.8 GPa, 393.6 ± 11.2 GPa and 50.9 ± 0.5 respectively.