Papers by Keyword: Diamond-Like Carbon (DLC)

Abstract: In this paper, various annealing conditions using Al-based (Ti/Al/Ti/Au=70nm/100nm /5nm/120nm) and Ni-based (Ti/Ni/Ti/Au=20nm/90nm/5nm/120nm) metal contacts to n-type and p-type ion-implanted 4H-SiC epi layers have been studied in the effort to optimize simultaneous ohmic contact formation with the lowest specific contact resistance (SCR) values. Values of 1.091×10^-4 Ω∙cm² and 1.158×10^-5 Ω∙cm² were achieved using Al-based Ohmic metal contacts for p-type and n-type 4H-SiC, respectively, at an annealing temperature of 950°C and under vacuum for 90 sec. Ohmic formation mechanisms were analyzed using the X-Ray Diffraction (XRD) surface analysis method, indicating Ti₃SiC₂ alloys to be the key intermediate layer formed at SiC/Ti interface, responsible for Ohmic properties to p-type SiC. The paper summarizes the metal process combinations possible for the formation of Ohmic contacts to both n-type and p-type 4H-SiC, offering various options in either using the same metal materials and/or common annealing conditions.

Abstract: In this paper, a titanium nitride film (TiN) monolayer film was deposited on a pure Tantalum (Ta) substrate with Ti as an intermediate layer by magnetron sputtering technique, and a Ta/Ti/DLC (diamond-like carbon)/Ti/TiN/DLC multilayer film was designed. Raman spectroscopy and scanning electron microscopy were used to observe the film structure and morphology. Friction and wear properties of Ta/Ti/TiN monolayer film and Ta/Ti/DLC/Ti/TiN/DLC multilayer film were analyzed by UMT-3 tester. The results show that the surface of multilayer film is denser and better bonded than TiN monolayer film. Under dry friction conditions, the friction coefficient of TiN monolayer film is stable at about 0.45. In contrast, the friction coefficient of DLC multilayer film remains around 0.15 with very small fluctuation during the whole friction process. This is determined by the inherent characteristics of DLC film, which is composed of sp²-C graphite structure and sp³-C diamond structure. From the analysis of the wear mechanism, the Ta substrate mainly undergoes adhesive wear and abrasive wear, however, the TiN monolayer film and Ta/Ti/DLC/Ti/TiN/DLC multilayer films mainly undergo abrasive wear mechanism. The friction coefficient of TiN monolayer fluctuates more than that of dry friction conditions in the body-liquid environment, and finally stabilize at about 0.5. The friction coefficient of DLC multilayer films does not differ much from those of dry friction conditions. This is because the TiN monolayer film generates a large amount of abrasive chips to fill the scratches in the body fluid environment, accompanied by the peeling and flaking of the compacted abrasive chips, thus the friction coefficient fluctuates greatly. The DLC multilayer films also undergoes graphitization transfer. In addition, the free hanging bonds of DLC film are passivated, which reduces the degree of adhesive wear. In summary, the DLC multilayer film has better biocompatibility, wear resistance, and stronger bonding.

Abstract: In this paper, evolution of optical and electrical properties of diamond-like carbon (DLC) films deposited by ECR-CVD system are reported. By varying the deposition different substrates bias (0, -55, -100 V) and volume amount of C₂H₂ from 40 to 55 cc onto substrate Si/TiN and quarts. The structure of the DLC films were analyzed from Raman spectroscopy. DLC films deposited bias at-100 V and C₂H₂ at 40 cc show excellent optical transmittance and high resistivity. As a result, I_D/I_G ratio corresponds to the optical transmittance and resistivity with I_D/I_G ratio decreased making the film like to the diamond. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting substrates bias and volume C₂H₂, is important to many applications, which is improve film properties.

Abstract: Nowadays environmental awareness issue draws the attention of the scientists; lubricant industry also focuses on environment friendly lubricating oils. Therefore, vegetable oils draw the attention of scientists because of environmental friendly as well as good lubricating characteristics. However, good lubricating vegetable oils often shows inferior property because of low thermal stability, hence, to enhance the performance of vegetable oils self-lubricating diamond like carbon coating is considered, which helps in lowering the friction force which in turn lower friction induced heating, as a result stability of vegetable oils increases. In this current research, three vegetable based oils (sunflower, palm, coconut) are considered as lubricating oil. Tribological tests are conducted by ball on plate tribo-testing machine, tetrahedral type diamond like carbon coated plates and uncoated balls are used in the tribo-pair. Among the testing conditions sunflower oil shows good friction and wear characteristics and coconut oil shows inferior friction and wear characteristics.

Abstract: A series of a-C:H:Zr-x coatings (the x in the term a-C:H:Zr-x is the Zr target current varied in the deposition process) have been deposited on AISI M2 steel used unbalanced magnetron sputtering system (UBMS). During deposition process, different a-C:H:Zr-x topcoats were deposited by varying the Zr target current from 0.0 A to 0.5A while maintaining the remaining process conditions at the constant settings. The microstructure, adhesion and tribological properties of the a-C:H:Zr-x coatings were found to vary with the Zr content. The tribological properties of the coatings had been tested against AISI 52100 or Si₃N₄ counterbody under ball-on-disk point contact wear mode using an oscillating friction and wear tester. Of the various coatings, the a-C:H:Zr-0.4 coating provided the best tribological properties, including the lowest wear depth, the friction coefficient and the longest lifetime. Compare to the coatings sliding against both counterbodies, all of coatings possessed the high wear depth as sliding against Si₃N₄, but it displayed longer wear lifetime than sliding against AISI 52100.

Abstract: The nitrogen-doped diamond-like carbon film was prepared on Ti6Al4V alloy by using plasma enhanced chemical vapor deposition (PECVD) technique,and its biocompatibility was studied.The surface morphology,chemical composition and contact angle were measured by scanning electron microscope (SEM),X-ray photoelectron spectroscopy(XPS),Raman Spectrometer and contact angle measuring device. Finally, the proliferation rate and cellular morphology of 3T3-E1 osteoblast cells on different sample surfaces were tested and Image J software was used to statistically analyze the count of the adhered cells. The results showed that cell adhesion and proliferation were significantly (P<0.05) increased on nitrogen-doped diamond-like carbon films , which illustrated that N doping improved the biocompatibility of DLC films. This finding has potential clinical application value to modify titanium alloy for new bone formation.

Abstract: The martensitic stainless steel X45CrSi93 is widely used in the automotive industry. One way to improve its properties is the deposition of high adhesiveness DLC films, which are well known for their excellent properties such as high hardness, low friction coefficient, chemical inertness, biocompatibility and excellent wear resistance. In this work, the adhesion between substrate and film was studied, by growing silicon interfaces with different deposition parameters. The technique used for growing these films was PECVD pulsed-DC. In order to obtain information of the silicon interface formation, ionic sub-implantation simulations were performed, by the software SRIM/TRIM. Raman spectroscopy was used to verify the atomic structure of the films. Scratch tribological test was performed to study adhesion. It was observed that the mechanical and tribological properties were greatly improved with the deposition of DLC films on the silicon interface. A correlation between the residual stress and adhesion of DLC films was found.

Abstract: This work illustrates a novel device for storing electronic charge and works as a non-volatile memory device. It is fabricated using an industrial technique and consists of silicon nanostructures and diamond like carbon (DLC) as a memory element and an ultra-thin barrier layer respectively. Both the silicon nanostructures and the DLC have been deposited by plasma enhanced chemical vapour deposition (PECVD) technique. The nanostructures are sandwiched between two DLC layers. To understand the ability of silicon nanostructures to store electronic charge current-voltage (I-V) and current-time (I-t) measurements were carried out. The memory effect is noted as the difference between the two electrical conductivity states (low ‘‘0’’ and high ‘‘1’’).

Abstract: Diamond-like carbon (DLC) films were prepared on the Si (100) substrates by pulsed cathodic arc plasma. The influences of given pulse frequency on the microstructure, morphology, mechanical and optical properties of DLC films were investigated by Raman spectroscopy, atomic force microscopy, Knoop sclerometer, X-ray double-crystal surface profilometer. The results showed that the variation of pulse frequency could significantly change the microstructure of DLC films, including the size and ordering of sp² carbon clusters and movement or diffusion of carbon atoms. The increasing of pulse frequency led to the variation of the relative fraction of Csp³/Csp². The hardness and internal stress of the DLC films were affected accordingly. The results might contribute to the synthesis of DLC films with excellent structure and properties by cathodic arc evaporation.

Abstract: Titanium is a hard-to-machine material. An improvement in tool life via advanced tool coating materials can lead to higher productivity of titanium. In this study, a Grade 5 Ti workpiece was milled using a diamond-like carbon coated (ta-C) cutting tool and its performance compared with the standard TiAlN coated endmill. It was found that a ta-C coated tool experienced higher cutting forces than the TiAlN coated tool; however, it showed slower rate of tool wear indicating better tool life and the possibility of achieving higher metal removal rates. Hence, it was concluded that the ta-C coated cutting tool performed better than the standard TiAlN coated tool.