Synthesis Of Silver-diamond Like Carbon Thin Films By Magnetron Sputtering

Abstract

Diamond-like carbon thin films are been used in wide range of applications due to their attractive tribological properties. Metal-doped DLC films have significant properties which make them compatible to use in larger variety of applications. The present study examines the dispersion and their effect on various tribological properties when Ag is incorporated into the DLC thin films. These Ag-DLC nanocomposite films were synthesized by a hybrid CVD and magnetron sputtering process in a discharge composed of CH4, and Ar atmosphere. These DLC and Ag-DLC films were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. Tribological tests were carried out to measure the frictional and wear behavior of the Ag-DLC films as a function of Ag content. The TEM cross sectional studies revealed that Ag is present as Ag nanoparticles that were distributed uniformly throughout an amorphous DLC matrix. XPS analysis confirmed that Ag in the nanoparticles was present in the metallic form. Increasing the Ag content in the film, reduced its sp3 content. The incorporation of these nanoparticles causes a reduction in hardness in Ag-DLC when compared with pure DLC films. Microhardness of DLC films exhibits values up to a maximum of 16 GPa and gradually decreases with increasing in Ag content. FTIR and Raman studies confirmed that the films contain a significant amount of hydrogen, and with an increase in the Ag content in the DLC film results in an increase in sp2 carbon content. Finally, the friction behavior of the Ag-DLC films showed a comparable performance with that of DLC films with a coefficient of friction as low as 0.1. The DLC films exhibited a lower wear rate of 5.51x10-8 mm3/Nm than Ag-DLC films. The wear rate in the Ag-DLC films gradually increased with increasing Ag content but it remained at low levels (i.e., up to 1.7x10-7 mm3/Nm). This is consistent with the higher sp2 content of the Ag-DLC films.