Structure characterization and antibacterial properties of Ag-DLC films fabricated by dual-targets HiPIMS

Abstract Silver doped diamond-like carbon (DLC) films were prepared on Si (111) substrates by dual-targets high power impulse magnetron sputtering (HiPIMS), and the chemical composition, microstructure, mechanical properties and antibacterial properties of the as-deposited films were obtained. When the sputtering voltage of the Ag target was varied from 450 to 580 V, X-ray photoelectron spectroscopy results revealed that the concentration of Ag in the as-deposited films was increased from 19.1 to 32.0 at. %. High resolution transmission electron microscopy images depicted that the as-deposited films were composed of Ag nanoparticles (AgNPs) embedded in DLC matrix. Along the cross-section of the film, the size of silver nanocrystals was varied from 5 ~ 12 (in the middle) to 2 ~ 5 nm (in the top surface). When the sputtering voltage was increased, the density of AgNPs was raised also. In addition, when the bias was increased from -50 to -100 V, the size of AgNPs in the top surface was reduced from 5 ~ 12 to 2 ~ 5 nm. AgNPs with a small size benefited the release of silver ions and improved the antibacterial ability, and the samples fabricated with the sputtering voltage (Ag target) of 500 ~ 560 V and a larger bias (-100V) obtained an excellent antibacterial efficiency (> 99.5%) against Escherichia coli and Staphylococcus aureus.