| Ion implantation can bring out changes in chemical status and structure of the material surface, resulting in the physical, chemical and mechanical properties without obvious interfaces between implanted layer and sbustrate. Therefore, ion implantation is a well known method to adulterate semi-conductor and modify material surfaces as well, which has been widely used both in scientific and industrial fields. In this study, plasma ion immersion and deposition was adopted to fabricate diamond like carbon film (DLC). Furthermore, tungsten implantations were used as pre-treatment of substrates and post-treatment of DLC films to improve the mechanical properties and adhesion strength. The composition, microstructure and mechanical properties of the systems have been systematically investigated. In addition, the strengthening mechanism has been explored on theory and the following results have been got.Firstly, plasma immersion ion implantation and deposition (PIII-D) has been utilized to produce DLC film directly on 316L steel substrates. Carbon ions have been implanted into the steel substrates,and display Gaussian distribution along the implanting direction, which is beneficial to the adhesion DLC films and steel substrates. Systematic studies have focused on the effects of both the negative bias voltage and the ratio of the acetylene to argon flow rates (FC2H2/FAr) on the properties of the films including surface morphology, structure and mechanical properties. The optimal parameters including the FC2H2: FAr ratio of 20:5 and the negative bias voltage of -20kV are determined from this study.Secondly, tungsten pre-implantation was conducted on steel substrates prior to the deposition of DLC film. A gradient WC interface was created that mitigates diffusion of the dissociated carbon atoms on the surface. Compared to the untreated sample, the adsorbed carbon atoms can more easily find suitable nucleation sites on the W-implanted substrate so as to be protected from re-evaporation. The film on the W-implanted steel shows the better behavior in the scratch tests. Thus, the adhesion strength can be dramatically improved. The pretreatment parameters also play an important role in the quality of the films. For similar deposition conditions, the film thickness and sp2 contents are affected from the amount of tungsten carbide. In our studies, pretreatment using W pre-implantation at a relatively high voltage of -20 kV and large implantation flux of 5×1017 ions-cm-2 favors film growth significantly. Subsequently, the DLC film possesses a higher sp3 content, smoother surface and improved adhesion strength.Last, tungsten doped amorphous carbon films are prepared on silicon (100) by post-implantation of tungsten ions into pure DLC using the plasma immersion ion implantation technique. After the above treatment, the peak concentration of tungsten reaches 27 at.% and W-C nanocrystallites with largest diameters of ~5 nm are formed in the near surface region of DLC films. Both the quantity and size of these nanocrystallites are observed to undergo unique transformation with increasing depths, enabling gradual release of the compressive stress and subsequently leading to better adhesion between the film and substrate. The formation mechanism of nanocrystallites is explained by ion implantation physics and thermodynamics. The combination of damage driving and chemical effects contribute to the distinguished structure of the amorphous carbon film embedded with nanocrystallites. Our results suggest an alternative means to produce W containing amorphous carbon films with gradient structures and improved mechanical properties.
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