Ti–Cu Coatings Deposited by a Combination of HiPIMS and DC Magnetron Sputtering: The Role of Vacuum Annealing on Cu Diffusion, Microstructure, and Corrosion Resistance

Lina Qin,Yantao Li,Nan Huang,Peipei Jing,Fengjuan Jing,Dong Xie,Bin Huang,Donglin Ma,Yongxiang Leng,Behnam Akhavan

doi:10.3390/coatings10111064

Abstract

Titanium-copper (Ti–Cu) coatings have attracted extensive attention in the surface modification of industrial and biomedical materials due to their excellent physical and chemical properties and biocompatibility. Here, Ti–Cu coatings are fabricated using a combination of high-power pulsed magnetron sputtering (HPPMS; also known as high power impulse magnetron sputtering (HiPIMS)) and DC magnetron sputtering followed by vacuum annealing at varied temperatures (300, 400, and 500 °C). X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) data showed that Ti, Cu, and CuTi3 are mainly formed in the coatings before annealing, while Ti3O, Cu2O, and CuTi3 are the main compounds present in the annealed coatings. The cross-sectional TEM micrographs and corresponding EDS results provided evidence that Ti is mainly present on the surface and interfaces of the silicon substrate and the Ti–Cu coatings annealed at 500 °C, while the bulk of the coatings is enriched with Cu. The resistivity of the coatings decreased with increasing the annealing temperature from 300 to 500 °C. Based on self-corrosion current density data, the Ti–Cu coating annealed at 300 °C showed similar corrosion performance compared to the as-deposited Ti–Cu coating, while the corrosion rate increased for the Ti–Cu coatings annealed at 400 and 500 °C. Stable release of copper ions in PBS (cumulative released concentration of 0.8–1.0 μM) for up to 30 days was achieved for all the annealed coatings. Altogether, the results demonstrate that vacuum annealing is a simple and viable approach to tune the Cu diffusion and microstructure of the Ti–Cu coatings, thereby modulating their electrical resistivity, corrosion performance, and Cu ion release behavior.

Highlights

Titanium and titanium-based alloys have been widely used in industries such as chemical and biomedical engineering due to their corrosion resistance, mechanical properties, elasticity, excellent thermal and chemical stability, as well as biocompatibility [1,2,3,4]
The sampling depth of EDS is in the range of micrometers [31,32], which is much larger than the thickness of the Ti–Cu coatings that was approximately 250 nm, as evaluated by cross-sectional transmission electron microscopy (TEM) images
Ti–Cu coatings were fabricated using high-power pulsed magnetron sputtering (HPPMS)/DC magnetron co-sputtering followed by vacuum annealing at temperatures of 300, 400, and 500 ◦ C

Summary

Introduction

Titanium and titanium-based alloys have been widely used in industries such as chemical and biomedical engineering due to their corrosion resistance, mechanical properties, elasticity, excellent thermal and chemical stability, as well as biocompatibility [1,2,3,4]. Titanium combined with copper in the form of thin Ti–Cu coatings has potential applications in surface engineering of devices to modify their mechanical, anticorrosion and antibacterial properties, as well as biocompatibility [11,12,13,14,15]. Vacuum annealing is a common method to change the microstructure, corrosion behavior, resistivity, mechanical properties and biocompatibility of materials [23,24]. It has been reported that annealing of Ti–Cu coatings with Ti concentration of 1.3 and 2.9 at.% in an argon atmosphere results in the segregation of the top and bottom of the coating, forming a supersaturated Ti layer suitable for self-forming barrier layers in integrated circuits [25]

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Results

Conclusion