Applications of DLC Films

Applications of DLC films in several fields like optics, magnetic disks, tribology and machine elements or biomedical purposes have been reported in the literature. A review on this topic was given by Matthews and Eskildsen [78]. 

The dominating field of appUcation at present is that of tribological coatings on machine parts and tools. This shall be discussed in more detail. However, for all applications of the coatings a sufficient adhesion is required. Therefore this question will be treated first in the next section. 

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Hirakuri, K.K. Yoshimura, M. Friedbacher, G. Application of DLC films as masks for integrated circuit fabrication. Diamond Relat. Mater. 2003, 12, 1013-1017. 

Friction coefficients, being not a physical property in the strict sense, but depending on the contact partners and many other external parameters, will be reported in the next section. The combination of low friction coefficients, typically < 0.2, with mechanical and surface properties which are partly polymer-like (elasticity, surface energy) and partly ceramic- or metal-like (hardness. Young modulus) qualitatively explains the outstanding position of DLC films as low-friction, highly wear-resistant coatings on which most of their present applications are based [77]. 

The application of Raman spectroscopy to the studies of diamondlike carbon (DLC) films has been reviewed in this volume (Chap. 22 and 24) and elsewhere [147]. Recent hardware developments involve the application of UV excitation to the study of DLC films [148-151]. Recently, a patent was granted to SI Diamond Technology [152] covering the application of UV-excited Raman spectroscopy for the characterization of carbon films used in the construction of a field-emission cathode. UV-excited Raman spectroscopy, however, is likely to be limited to the research environment due to the cost and complexity of the instrumentation. 

Initial experiments on DLC were conducted with Raman microprobes however, the opportunity afforded by the application of Raman spectroscopy for the measurement of DLC film properties have led to a number of instrument companies introducing nonmicroscope-based analyzers tailored specifically for this market. Raman microscope systems are currently extensively used in the area of failure analysis. In this application, the high spatial resolution obtainable with a Raman microprobe is useful for the identification of small defects and contaminants. 

Diamond-like carbon since its inception in 1962 has found applications in some very important areas. These applications include coatings used in scratch-resistant optics, razor blades, prosthesis in medical applications electron emission surfaces in electronics as an insulator material for copper heat sinks in semiconductors such as solar cells and sensors for visible to infrared radiations and as structural materials such as deuterated DLC film used for neutron storage in advanced research instrumentation. As technology matures the unique properties of DLC will find new and important applications. 

Due to their chemical inertness, high abrasion resistance, low friction and good biocompatibility DLC films are very promising candidates for biomedical applications. For example, femoral heads of hip protheses have been coated successfully with DLC to reduce the production of small wear particles, which can lead to reactions on a cellular level. Furthermore DLC was shown to be a potential material for artificial heart valves where the films must be non-thrombogenic and must have a long-time stabihty in contact with blood [93]. Mitura et al. [94] investigated DLC... 

Within the last several years, a number of companies have investigated the application of Raman spectroscopy to process analysis. A review of the scholarly and patent literature reveals several examples PCI3 reactions, titanium dioxide production, diamondlike carbon (DLC) films production, polymeric fiber property detection, applications to gasoline, aromatic production, chlorosilane production, and gas-phase measurements. In Section in, some of these applications will be reviewed in order to illustrate the application of Raman spectroscopy to process chemistry and control. 

Thin carbon films are applied to materials to enhance their abrasion resistance (Chap. 22). The specific case of industrial application of Raman spectroscopy to studies of DLC is extensively reviewed in Chapter 24. Brief mention is made here because of the long history and the widespread QA/QC use of Raman systems in the hard-disk DLC business, however. The reader is referred to these additional chapters for a comprehensive review of Raman spectroscopic studies of DLC. 

DLC coatings are already in production in several areas (optical and IR windows) and appear particularly well-suited for abrasion and wear applications due to their high hardness and low coefficient of friction. They have an extremely smooth surface and can be deposited with little restriction of geometry and size (as opposed to CVD diamond). These are important advantages and DLC coatings will compete actively with existing hard coatings, such as titanium carbide, titanium nitride, and other thin film... 

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