Effect of Silver Clusters Deposition on Wettability and Optical Properties of Diamond-like Carbon Films

In this study, the effect of silver clusters deposition was investigated on optical, wettability and surface properties of diamond-like carbon (DLC) films. Silver clusters and DLC films were deposited on Ni-Cu (70.4-29.6;W/W) alloy substrates by ion beam sputtering deposition (IBSD) technique. Optical and structural properties were measured using UV-visible spectroscopy and Raman spectroscopy, respectively. The wettability and surface free energy of films were determined by the contact angle (CA) measurements. Raman spectra of DLC thin film with 121±6nm thickness without accumulated Ag showed that the size of the graphite crystallites with sp 2 bands (La) was 3.36Å by the ID/IG ratio equal to 0.062 with large optical band gap equal 3eV extracted from Tauc relation. The results of the deposition Ag in the various ion beam energy between 0.6 to 2keV showed the Ag clusters were accumulated uniformity on the surface of DLC films at 0.9keV.  The volume percentage of silver clusters was varied from 5.0±2.01 to 16.3±1.4. The variation was caused by controlling the screen voltage and the deposition time. The CA of the deposited films increases from 79°±2 to 95°±2 as well as the reflection values in the visible and near-infrared region due to the increase in the Ag concentration in the surface of DLC films; while the surface free energy decrease from 86±1 to 66±2mJ/m2  and the optical transmittance is almost constant. Our results demonstrate that the deposition of silver particles on DLC films is potentially useful for biomedical applications having good hydrophobic characteristics without causing a destructive effect on the optical properties of DLC films.