Effect of nitrogen flow rate on structure and mechanical properties of Mo–Al–Si–N films prepared by direct current magnetron sputtering

• Mo–Al–Si–N films were deposited at different nitrogen flow rates.
• Nitrogen flow rate has strong influence on the preferred orientation of films.
• The lattice parameter of films increases with the increase of the nitrogen flow rate.
• Mo–Al–Si–N films have better toughness at a nitrogen flow rate of 15 sccm.
• The hardness of films reaches a maximum value at a nitrogen flow rate of 15 sccm.

Mo–Al–Si–N films were deposited by direct current magnetron sputtering using different nitrogen flow rates. The structure and mechanical properties of these films were investigated by means of X-ray diffraction, field emission scanning electron microscopy, field emission electron probe microanalysis and nanoindentation. The results indicate that the deposition rate decreases from 24.5 to 11.8 nm/min with increasing nitrogen flow rate from 7.5 to 30 sccm, while the grain size of films decreases firstly from about 24 to 14 nm and then increases to about 25 nm. The preferred orientation of the Mo–Al–Si–N films changes from (111) to (200) due to the increase of surface energy and the decrease of strain energy. The lattice parameter increases from 4.177 to 4.186 Å due to the excess nitrogen atoms occupying interstitial positions of Mo–Al–Si–N films. It is worthy to note that Mo–Al–Si–N films deposited using a nitrogen flow rate of 15 sccm display higher hardness and better toughness, which are mainly determined by the grain size.