Abstract
Monolithic Hf–Si–N coatings and multilayered Hf–Si–N coatings with cyclical gradient concentration were fabricated using reactive direct current magnetron cosputtering. The structure of the Hf–Si–N coatings varied from a crystalline HfN phase, to a mixture of HfN and amorphous phases and to an amorphous phase with continuously increasing the Si content. The multilayered Hf48Si3N49 coatings exhibited a mixture of face-centered cubic and near-amorphous phases with a maximal hardness of 22.5 GPa, a Young’s modulus of 244 GPa and a residual stress of −1.5 GPa. The crystalline phase-dominant coatings exhibited a linear relationship between the hardness and compressive residual stress, whereas the amorphous phase-dominant coatings exhibited a low hardness level of 15–16 GPa; this hardness is close to that of Si3N4. Various oxides were formed after annealing of the Hf–Si–N coatings at 600 °C in a 1% O2–99% Ar atmosphere. Monoclinic HfO2 formed after Hf54N46 annealing and amorphous oxide formed for the oxidation-resistant Hf32Si19N49 coatings. The oxidation behavior with respect to the Si content was investigated by using transmission electron microscopy and X-ray photoelectron spectroscopy.
Highlights
The group IVB (Ti, Zr and Hf) metal nitride coatings possess extraordinary characteristics of hardness [1,2,3,4], corrosion resistance [5,6,7] and decoration [8], but demonstrate inadequate oxidation resistance [9,10]
Hf–Si–N coatings have been applied as gate electrodes [15,16], corrosion-resistant films [17] and biocompatible films [18], few studies have focused on improving their oxidation resistance
In a 1% O2 –99% Ar atmosphere for up to 100 h of annealing. These Zr–Si–N coatings with a cyclical gradient concentration fabricated using cosputtering with a low substrate holder rotation speed formed a multilayered structure consisting of alternatively-stacked high- and low-Si-content sublayers, which exhibited the characteristics of high oxidation resistance and mechanical properties, respectively [19]
Summary
The group IVB (Ti, Zr and Hf) metal nitride coatings possess extraordinary characteristics of hardness [1,2,3,4], corrosion resistance [5,6,7] and decoration [8], but demonstrate inadequate oxidation resistance [9,10]. In our previous study [19], Zr–Si–N coatings of 15–30 at.% Si maintained near-amorphous phases as examined through X-ray diffraction and exhibited excellent oxidation resistance at 600 ◦ C in a 1% O2 –99% Ar atmosphere for up to 100 h of annealing. These Zr–Si–N coatings with a cyclical gradient concentration fabricated using cosputtering with a low substrate holder rotation speed formed a multilayered structure consisting of alternatively-stacked high- and low-Si-content sublayers, which exhibited the characteristics of high oxidation resistance and mechanical properties, respectively [19]. The sputter etching rate was set at 9.5 or 25.6 nm/min for SiO2
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