Low-temperature deposition of ZrN coatings on plasma-treated polymeric substrates

In this study, ZrN coatings were deposited on polycarbonate substrates using a low-temperature reactive sputtering method. This research represents the first investigation of ZrN coatings on uncoated polymers. Deposition conditions and plasma etching treatments were optimized to achieve high-quality, defect-free, and highly adhesive bright golden ZrN coatings. Two critical parameters, substrate voltage and treatment time, were explored during Ar + N 2 plasma etching of PC surfaces, prior to the depositions. Plasma etching of PC for 2 min in floating and bias modes resulted in ZrN coatings with pronounced cracking patterns, more prominent under floating conditions. By applying a 70 V substrate bias and varying the treatment time from 2 to 11 min, cracking in the coatings was progressively reduced, achieving a crack-free surface at 8 min, with higher total reflectivity and lower diffuse reflectivity. Cracking in the coatings was attributed to compressive stresses. Structural analysis revealed (111)-oriented grains under compressive stress for the 2-min treatments, transitioning to unstrained (200)-oriented grains at 5 and 8 min. The surface roughness of the polymer influenced grain orientation, with smoother surfaces promoting (200) orientation. Minimal roughness observed at 8 min indicated superior coating quality. All coatings showed excellent adhesion and colour fastness. • ZrN coatings were deposited on uncoated polymers, for the first time in literature. • Deposition conditions were carefully optimized to enable low-temperature operation. • Plasma etching treatment time and bias voltage were systematically varied. • Optimal etching conditions resulted in crack-free coatings with (200) and (111) preferential orientations. • ZrN coatings exhibited excellent colour fastness and adhesion.