Growth and properties of nanocrystalline TiN—amorphous Si < inf > 3 < /inf > N < inf > 4 < /inf > composite thin films deposited on IN718 and phynox alloy substrates

Abstract

TiN/Si3N4 composite thin films were deposited on Inconel718 (IN718) and flexible Phynox alloy substrates by the co-sputtering process at room temperature and 250 °C. The TiN films were sputtered from a Ti target, while the Si3N4 films were sputtered from either a Si or a Si3N4 target. The aim is to prepare composite thin films of nanocrystalline TiN and amorphous Si3N4 under the same conditions of pressure and temperature. This objective was achieved at room temperature and 250 °C substrate temperature on both the substrates mentioned above, as confirmed from x-ray and selected area electron diffraction patterns when the targets used were Ti and Si3N4. Significantly, crystallization of Si3N4 phase was observed under favorable conditions when Si was the target. All the films exhibit columnar microstructure comprising layers of TiN and Si3N4. Films deposited from the Si target crystallize at a lower thickness than those deposited from the Si3N4 target. There is a substrate type, substrate temperature, and deposition time dependence of grain size. The films on Phynox substrates have smaller grain sizes (50–60 nm) in comparison with films on IN718 substrates (100–120 nm). The films deposited on the IN718 substrates display higher surface roughness than the films deposited on the Phynox substrates which, in turn, depended on the target from which the Si3N4 films were deposited. The hardness of composite films in which the Si3N4 is deposited from the Si target is higher than that for the films deposited from the Si3N4 target. The present work, thus, describes a technique for the single layer nanocomposite thin films deposition with properties that can be tuned by the type of target used.