Structure–Property Relationships of Tungsten Nitride Coatings on Copper Substrates Prepared by Reactive Direct Current Magnetron Sputtering

Abstract

Tungsten nitride (WN) coatings were deposited on copper substrates by reactive direct current magnetron sputtering using deposition times of 15, 30, 45, and 60 min. The influence of deposition time on the structural, morphological, and electrical properties of the coatings was systematically investigated. WN coatings with thicknesses increasing from approximately 0.45 to 1.60 μm were obtained as the deposition time increased. Energy-dispersive X-ray spectroscopy confirmed the presence of W and N in the coating region, while X-ray diffraction showed diffraction features consistent with a crystalline hexagonal δ-WN phase with a dominant {110} preferred orientation for all samples. Increasing deposition time was accompanied by a decrease in the lattice parameter from 2.934 to 2.922 Å and in the relative lattice strain from 0.014 to 0.010. Atomic force microscopy showed that coatings deposited for 15 and 30 min reduced the initial surface roughness, whereas longer deposition times promoted the development of larger surface features and increased roughness. Electrical impedance measurements showed a strong frequency-dependent response. Electrical impedance exhibited a pronounced frequency dependence. At the 1000 kHz range, the impedance magnitude was approximately 0.54 Ω, 0.43 Ω, 0.45 Ω, and 0.43 Ω for coatings deposited for 15, 30, 45, and 60 min, respectively. The electrical response was correlated with the evolution of lattice strain and structural characteristics, although the present data not establish a unique charge-transport mechanism. These findings indicate that deposition time is an important parameter for tailoring the structural and electrical response of WN coatings for conductive and protective applications.