The effects of Si incorporation on the thermal and tribological properties of DLC films deposited by PBII&D with bipolar pulses
Introduction
The thermal degradation of diamond-like carbon (DLC) films is a major problem in achieving high temperature applications. It has been reported that DLC films maintain stable properties up to about 400 °C while the graphitization of the films starts above this temperature [1]. It is required that DLC films should endure at least up to 500 °C in ambient air to achieve high temperature applications such as coating materials for molds. Though many studies have been carried out to understand the high temperature behavior of DLC films, most of the studies have dealt with their thermal stability in a vacuum or inert gas conditions [2], [3], [4].
In the present study, the thermal and tribological properties of silicon-incorporated DLC films in ambient air were investigated. The DLC films were deposited using a bipolar-type plasma based ion implantation and deposition (PBII&D) technique, and the effect of the Si content on the thermal stability of the DLC films was investigated.
Section snippets
Experiments
A bipolar-type PBII&D system [5] was used for the deposition of DLC films on steel and Si substrates. The steel substrates were used for the friction measurements. The deposition conditions of the DLC films are shown in Table 1. The deposited DLC films were annealed at 500 °C for 30 min in ambient air. The composition and microstructure of the DLC films were investigated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The hardness of the films was measured by
Structure and composition of the DLC films
Raman spectra of the DLC films before and after annealing are shown in Fig. 1. The as-deposited DLC film without Si (pure DLC) shows a typical diamond-like structure with peaks centered at 1539 (G band) and 1373 cm− 1 (D band). With the increasing Si content, the G peak becomes more pronounced relative to the D peak, and the peak for the 29 at.% Si-DLC film can be fitted by a single Gaussian, which has also been reported by Camargo et al [2]. Also, the intensity ratio, Id/Ig, decreases from 0.81
Conclusions
The silicon-incorporated DLC films were deposited using a bipolar-type plasma based ion implantation and deposition (PBII&D) technique, and the thermal stability and tribological properties of the films with respect to the Si content were investigated. The major results obtained are as follows.
- (1)
Raman spectral analysis and the hardness measurements revealed that the structure and mechanical properties of the Si-DLC films with a Si content greater than 21 at.% are not affected by thermal annealing
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