Nitrogen Incorporation Induced Soft-to-Hard Transition Observed in the Mechanical Properties of Amorphous Niobium Oxide Films
The article covers the nitrogen incorporation induced transformation of mechanical behavior of the amorphous Nb-oxide films. Niobium oxynitride (Nb-O-N) films were sputter-deposited using a metallic Nb target in the presence of oxygen and nitrogen. The nitrogen concentration in the Nb-O-N films was varied by adjusting the nitrogen gas flow rate from 0 sccm to 10 sccm while keeping total gas flow (nitrogen + oxygen + argon) constant at 30 sccm. The surface and interface chemical characterization of the samples indicate that, with increasing the nitrogen content, the corresponding mechanical characteristics, namely, hardness (H) and elastic modulus (E), increase from ~ 5 GPa to 15 GPa and 115 GPa to 135 GPa, respectively. The trend observed in H and E values correlates with Nb-O and Nb-N bond formation in Nb-O-N as evidenced in chemical analyses made using x-ray photoelectron spectroscopy. The chemical composition measurements indicate that nitrogen incorporation proceeds with a decrease in relative oxygen content in Nb-O-N films, where the ability to withstand mechanical deformation is enhanced. A correlation between the processing conditions, nitrogen content, and physical/mechanical properties in Nb-O-N films is established.
The authors acknowledge, with pleasure, support from the National Science Foundation (NSF) with NSF-PREM Grant #DMR-1827745.
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