XPS study of ultrathin carbon films prepared by filtered cathodic vacuum arc

Abstract

Diamond like carbon (DLC) films have attracted increasing attention in a variety of industries due to their excellent mechanical and chemical properties. To meet the demands from the emerging industries, such as micro electro mechanical systems (MEMS), a considerable number of research studies have been conducted to advance the technology for thin DLC films fabrication. However, it has been reported that the properties of DLC films vary with thickness, which necessitate further understanding of the mechanism of initial film growth. To elucidate the mechanism of carbon film growth, the present study employs X-ray photoelectron spectroscopy (XPS) to characterize two types of amorphous carbon films fabricated by cathodic vacuum arc discharge and radio-frequency magnetron sputtering. The results indicated that wide range of energy distribution of carbon ions in the cathodic arc discharge caused a decline in the sp 3 ratio with decreasing thicknesses.

Properties and Classification of Diamond-Like Carbon Films

“…The nano-indentation hardness was not significantly high in regions with high hydrogen content, even when the sp 3 ratio was large. Thus, it was difficult to predict the properties of amorphous carbon by estimating the sp 3 ratio using NEXAFS, X-ray photoelectron spectroscopy (XPS) [ 89 , 90 , 91 ], and electron energy-loss near-edge structure [ 92 ]. Importantly, the estimation of hydrogen content played a crucial role in characterizing amorphous carbon.…”

Mechanical characterization of segment-structured hydrogen-free a-C films fabricated by filtered cathodic vacuum arc method

“…In this present study, the structure of the 200-nm-thick film can be modeled same as a hydrogen-free ta-C film from the work of Yasui et al [23]. They reported that the hydrogen-free ta-C film deposited by the FCVA method exhibits two sublayers known as sp 2 -rich surface layer and sp 3 -rich layer located below this sp 2 -rich surface layer.…”

“…In the FCVA method, the energy distribution of the carbon ions in the cathodic arc discharge has a wide range. The irradiation of high-energy ions during deposition contributes to film growth by forming a sp 3 -rich bulk layer, while low-energy ions resulted in the formation of a soft surface layer with high sp 2 bonding [23].…”

Tribological Characteristics of Ultra-thin DLC Films Prepared by Filtered Cathodic Vacuum Arc

“…The graphite target was sputtered by Ar plasma at an RF power of 200 W, an Ar mass flow rate of 50 seem, and a pressure during the sputtering of 0.6 Pa. In the case of sputtering, the depositing atoms have an energy of several eV, i.e., lower than that in FCV A [7], which leads to lower s/ bonding ratio in the film [5].…”

“…The present study aims to verify the relationship between the increase in COF and the various froperties that change with film thickness, such as the sp ratio [5], surface roughness, and thickness itself, under a normal load, which does not cause explicit plastic deformation on the surface, and finally identify the critical parameter 523 that accounts for nano-tribological behavior of ultrathin DLC films.…”