Study of room-temperature deposited ZrNx thin films

Abstract

Zirconium nitride (ZrN) has attracted scientific interest due to its diverse physical and functional properties. Despite the energetic favourability of room-temperature synthesis of ZrN_x, only a handful attempts have been made to understand the low-temperature synthesis protocols. In the present work, we synthesized a series of Zr–N thin films by varying partial N₂ gas flow (RN₂) at room temperature (300 K). The structural and compositional characteristics of resulting Zr–N films were studied. The investigation combines X-ray reflectivity (XRR), X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) measurements, which includes X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and variable angle spectroscopic ellipsometer (VASE). XRR results reveal the effects of varying RN₂ on deposition rate, providing insights into the formation of ZrN phase. XRD patterns reveal the structural evolution from the hcp Zr to fcc ZrN phase. Further, structural parameters, including lattice parameter and crystallite size are systematically examined, revealing high-quality nature of the films, with optimal results observed in RN₂ = 5–10% samples. XAFS measurements, particularly XANES of N and Zr K-edges, provide insights into the local environment, showing a centrosymmetric structure with octahedral symmetry within the ZrN films. Shifting of pre-edge features in the XANES spectra suggests variations in the oxidation state, implying a complex interplay between Zr and N atoms within the films. Emphasizing the importance of EXAFS, this study showcases its reliability for quantitative analyses. The technique unravels atomic coordination and bond lengths within the Zr–N films, which is crucial for a comprehensive understanding of the film’s structural characteristics. VASE measurement was done to understand the optical behaviour from the real and imaginary parts of permittivity spectra.