Effect of deposition pressure on the microstructure, mechanical, and corrosion properties of tantalum nitride thin films deposited by reactive pulsed laser deposition

Tantalum nitride films have several beneficial properties that make them attractive for various applications, where protective coatings with excellent film integrity and corrosion resistance are essential. This study investigates the influence of deposition pressure (2, 5, and 8 mTorr) on the characteristics of tantalum nitride films synthesized by pulsed laser deposition in a pure nitrogen atmosphere. Microstructural analysis confirmed that extremely smooth films were produced, with increasing crystallinity correlated with higher deposition pressures. Grazing incidence X-ray diffraction and selective area electron diffraction analysis confirmed the formation of distinct phases, specifically hexagonal gamma-Ta2N and cubic delta-TaN, in the deposited nanofilms. Decrease in hexagonal gamma-Ta2N phase content from 90 wt% at 2 mTorr to 60 wt% at 8 mTorr was observed with corresponding increase in cubic delta-TaN phase content. The hardness and modulus of films were increased with increasing deposition pressure. Electrochemical studies conducted in 3.5 wt% NaCl solution indicated that the tantalum nitride film-coated titanium deposited at 2 mTorr exhibited a similar to 6.4 times reduction in corrosion rates compared to uncoated titanium. Overall, the results suggest that deposition pressure significantly influenced the characteristics of the deposited films, indicating that the synthesis conditions can be effectively optimized for specific coating applications based on desired properties.