Structure and Properties of Ta–Si–N Coatings Produced by Pulsed Magnetron Sputtering

Abstract Coatings have been deposited by pulsed magnetron sputtering (PMS) of a TaSi2 ceramic target with a diameter of 120 mm on model silicon substrates in the ratio of gas flow rates of Ar/N2 = 1/2 and frequencies f = 5, 50, and 350 kHz. The structure and composition of the coatings are studied by scanning electron microscopy (SEM), energy–dispersive analysis, and glow discharge optical emission spectroscopy. The phase composition is determined by X-ray diffraction using CuKα radiation. The mechanical properties are measured by nanoindentation using a Nano Hardness Tester equipped with a Berkovich indenter at 4 mN load. The oxidation resistance of the coatings are estimated by isothermal annealing carried out in air in a muffle furnace at 1200°C, and the oxidation resistance is determined by the structure and thickness of the oxide layer. The results of structural studies suggest that the coatings are X-ray amorphous and have a dense homogeneous structure. The increase in frequency from 5 to 350 kHz results in a reduction in thickness and growth rate of the coatings. The specimens deposited at f = 5 and 50 kHz show high mechanical properties: hardness of 23–24 GPa, elastic modulus of 211–214 GPa, and elastic recovery of 75–77%. The coating obtained at the maximum frequency exhibits a hardness of 15 GPa, elastic modulus of 138 GPa, and elastic recovery of 65%. Annealing processes result in the formation of protective oxide layers such as SiO2, Ta2O5, and TaO2. The crystallization of the TaSi2 phase is pronounced, as is evidenced by X-ray diffraction analysis. The specimens deposited at f = 5 and 50 kHz demonstrate a small thickness of the oxide layer (0.9 and 1.1 μm), suggesting good oxidation resistance of the coatings at 1200°C.