Metal (Ag/Ti)-Containing Hydrogenated Amorphous Carbon Nanocomposite Films with Enhanced Nanoscratch Resistance: Hybrid PECVD/PVD System and Microstructural Characteristics

Abstract

This study aimed to develop hydrogenated amorphous carbon thin films with embedded metallic nanoparticles (a–C:H:Me) of controlled size and concentration. Towards this end, a novel hybrid deposition system is presented that uses a combination of Plasma Enhanced Chemical Vapor Deposition (PECVD) and Physical Vapor Deposition (PVD) technologies. The a–C:H matrix was deposited through the acceleration of carbon ions generated through a radio-frequency (RF) plasma source by cracking methane, whereas metallic nanoparticles were generated and deposited using terminated gas condensation (TGC) technology. The resulting material was a hydrogenated amorphous carbon film with controlled physical properties and evenly dispersed metallic nanoparticles (here Ag or Ti). The physical, chemical, morphological and mechanical characteristics of the films were investigated through X-ray reflectivity (XRR), Raman spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) and nanoscratch testing. The resulting amorphous carbon metal nanocomposite films (a–C:H:Ag and a–C:H:Ti) exhibited enhanced nanoscratch resistance (up to +50%) and low values of friction coefficient (<0.05), properties desirable for protective coatings and/or solid lubricant applications. The ability to form nanocomposite structures with tunable coating performance by potentially controlling the carbon bonding, hydrogen content, and the type/size/percent of metallic nanoparticles opens new avenues for a broad range of applications in which mechanical, physical, biological and/or combinatorial properties are required.

Synthesis and Characterization of Hydrogenated Diamond-Like Carbon (HDLC) Nanocomposite Films with Metal (Ag, Cu) Nanoparticles

“…The optical properties of hydrogenated amorphous carbon are governed by their bonding characteristics and the hybridization of the carbon atoms, and specifically the sp 3 /sp 2 ratio and the composition of hydrogen. The sp 3 fraction of our samples was estimated in a previous work [21] by Raman spectroscopy and it was in the order of 50%, while the hydrogen content was 20%-25%. The above results place the samples under the category of HDLC films.…”

“…In line with the NP source, a quadrupole mass spectrometer (MesoQ, Mantis Deposition Ltd., Thame, UK) was used to detect the mass distribution of the formed NPs and act as a filter with accuracy 0.2% in size. This hybrid deposition system was presented into more detail in a previous publication [21].…”

“…The addition of metal nanoparticles in an amorphous carbon matrix (hydrogenated or not) can lead to multifunctional materials with properties such as high catalytic activity [17], enhanced solar absorption [18,19] and nanoscratch resistance [20][21][22][23], among others. For photonic and plasmonic applications especially, a transparent HDLC matrix is desired in order to support the localized surface plasmon resonance (LSPR) of metallic NPs, such as Au, Ag and Cu.…”

“…The absence of the LSPR manifestation in lower metal concentrations we believe is due to the reduction of the HDLC transparency. The introduction of metals in the HDLC matrix induces graphitization [21,[28][29][30], which in turn reduces the optical transparency of the films due to π-π* transition [11] (of the sp 2 network). For low metal contents, the concentration of plasmonic NPs is not enough to overcome the loss of transparency.…”

Fluence Enhanced Optical Response of Ag Implanted Amorphous Carbon Thin Films

“…Noble metals-containing nanostructured materials have attracted great attention of researchers in the past few decades [14][15][16][17][18][19][20][21] because the metal nanoparticles exhibit a pronounced resonance extinction of visible light due to the collective excitation of quasi free electrons of the metallic system [22][23][24]. This phenomenon causes the absorption and scattering intensities of the metal nanoparticles to be much higher than that of identically sized non-plasmonic nanoparticles [25].…”