Study the effect of thermal annealing on adhesion strength of Silver-Tantalum Oxide thin film deposited by reactive magnetron sputtering

Abstract

Stainless steel (SS) are extensively used for healthcare, hygiene and surgical applications due to their excellent corrosion resistance and adequate mechanical strength. Among this class SS 316 L is employed most widely, due to highest corrosion resistance, good mechanical properties, resistance to sensitization and ease of fabrication. To incorporate antimicrobial characteristic in SS 316 L based surgical tools a nanocomposite layer comprising of Silver (Ag) and Tantalum oxide (TaxOx) has been deposited by using Physical Vapor Deposition (PVD) magnetron sputtering. Delamination of ceramic layers on SS 316 L substrate is one of the major limitation arising from insufficient crystallization and poor adhesion strength. PVD magnetron sputtering has been employed to develop 5.49 µm thick Ag-TaxOx nanocomposite layer on SS 316 L. Substantially improved adhesion strength has been achieved by controlling thermal treatment. The microstructure, surface and phase analysis of as-sputtered and annealed thin films has been carried out to determine the characteristics of the developed layer. A nanocomposite layer on SS 316 L substrate comprising of Ag and TaxOx has been achieved by releasing O2 during deposition. Thermal treatment was performed at 300, 400, 500 and 600 °C which progressively increased the crystallinity and segregation of Ag at the surface. Highest adhesion strength was achieved by annealing the coated samples at 400 °C, which exhibited four-fold increased adhesion strength when compared to as-deposited layer. The precipitation of a new phase Silver tantalum oxide (AgTaO3) was observed for the samples annealed at temperature above 400 °C, which may be responsible for the decrease in adhesion strength.