Examining the microstructure, morphological features, and wetting characteristics of Ti/TiN/TiAlN thin films produced through RF/DC magnetron co-sputtering

Abstract

This study reports synthesizing and characterizing Ti/TiN/TiAlN thin films deposited on 316 L stainless steel and silicon wafer substrates using the reactive RF/DC magnetron sputtering technique. The films' microstructure, morphology, thickness, roughness, and wettability were investigated experimentally and theoretically using density functional theory (DFT) calculations with the CASTEP program. X-ray diffraction analysis confirmed the formation of the fcc-TiAlN phase for coatings deposited at a DC power of 100 W, while increasing DC power to 150 W resulted in the appearance of a second phase, w-AlN. Field emission scanning electron microscopy images showed the formation of nanostructured coatings with a grain size range of 70–100 nm. The morphology of coatings was altered from a pyramid-like structure to a cauliflower structure by increasing the nitrogen amount in the N2/(Ar+N2) flow ratio. An increase in aluminum amount by increasing the DC power to 150 W enhanced the deposition rate and thickness of the coatings. The coatings deposited at a high N2/(Ar+N2) flow ratio exhibited minor surface roughness attributed to the compact structure. The contact angles obtained from the fabricated Ti/TiN/TiAlN coatings ranged from 86.2° to 114.2°, demonstrating values higher than the contact angle of uncoated 316 L stainless steel, which measured at 82°. Theoretical analysis using DFT calculations with CASTEP provided a fundamental understanding of the thin films' electronic structure and properties, consistent with the experimental results. This study highlights the importance of combining practical and theoretical analyses for a comprehensive understanding of material properties and the design of materials for various applications.