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

Georgios Constantinides,Apostolos Avgeropoulos,Marios Constantinou,Loukas Koutsokeras,Pantelis Kelires,Panos Patsalas,Constantinos Varotsis,Dimitrios Moschovas,Petros Nikolaou

doi:10.3390/nano8040209

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.

Highlights

Hydrogenated amorphous carbon (a–C:H) thin films consist of carbon and hydrogen elements, where carbon atoms form dangling bonds with hydrogen or sp1, sp2, and sp3 bonds with other two, three or four carbon atoms, respectively
Amorphous carbon films with a significant percentage of sp3 hybridization, commonly referred to as diamond like carbon or DLC/diamond-like a–C:H (DLCH) in short, possess excellent properties like high stiffness and hardness, low coefficient of friction, high wear resistance, chemical inertness, low permeability, high melting point, optical transparency in infra-red (IR), high electrical resistivity and thermal conductivity [2,3,4]. These exceptional properties led to a series of industrial applications like protective coatings on microelectromechanical systems (MEMS), razor blades, hard disc drives and biomedical implants to gas barriers in polyethylene terephthalate (PET) bottles [5,6,7]
We aimed to develop a new generation of a–C:H:Ag and a–C:H:Ti films with improved combination of properties and performance

Summary

Introduction

Hydrogenated amorphous carbon (a–C:H) thin films consist of carbon and hydrogen elements, where carbon atoms form dangling bonds with hydrogen or sp, sp2, and sp bonds with other two, three or four carbon atoms, respectively. Amorphous carbon films (hydrogenated or not) with a significant percentage of sp hybridization, commonly referred to as diamond like carbon or DLC/DLCH in short, possess excellent properties like high stiffness and hardness, low coefficient of friction, high wear resistance, chemical inertness, low permeability, high melting point, optical transparency in infra-red (IR), high electrical resistivity and thermal conductivity [2,3,4]. These exceptional properties led to a series of industrial applications like protective coatings on microelectromechanical systems (MEMS), razor blades, hard disc drives and biomedical implants to gas barriers in polyethylene terephthalate (PET) bottles [5,6,7]

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