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 arrow07b.gif What is Diamond Coating?      arrow07b.gif Process      arrow07b.gif  Advantage    arrow07b.gif Materials    arrow07b.gif  Applications 



What is diamond coating?

   Diamond is the hardest known material and consequently has been used as is an ideal abrasives for its highest hardness. Also, diamond is the best thermal conductor while it and is a good electric insulator. This unique property stems from its different thermal conduction mechanism with that of metals. While heat is transferred by free electron in metals, heat is transferred by phonon in the diamond. Because diamond is composed of light carbon atoms and the bond strength is very high, heat is quickly transferred by the lattice vibration. This highest thermal conductivity makes diamond the most promising material for heat-sink application. The high phonon speed is closely related with sound velocity and diamond is also promising material for speaker diaphragm for high tone (tweeter) speaker diaphragms. Also diamond is transparent to electromagnet radiation ranging from X-rays to IR ,thus  which is making it suitable for applicable to X-ray or IR windows. Besides, diamond is also promising for high temperature-high speed electronic devices because of its low dielectric constant, high hole mobility, and wide band gap.

There were early attempts to synthesize diamond from the 19th century. However, since the high pressure and temperature required for diamond synthesis was not available possible at that time. it was not until 1955 by that Bundy et. al., the first successfully synthesized the first man-made diamond was synthesized. Later, powder type diamond was synthesized by the detonation method16 in Russia, and Consequently, the synthetic diamond industry has grown steadily and in some applications provides an substituting alternative to natural diamond. However, since products of synthetic diamond by HT-HP methods are limited to powder or particle type, its applications were confined mainly to abrasives or cutters only.

 With the advent of the cutting edge technologies, the trend is that the industrial needs for materials are moving from bulk to thin film. Research on the low temperature synthesis of diamond started from in the 1950s. However, at that time, the gas activation process was not employed and the instead diamond was deposited on the seed crystals by pyrolysis of hydrocarbon. This utilized the low activation energy barrier of diamond nucleation than that of compared to graphite nucleation on the seed crystal.  But However, the substrate was confined to diamond only and once graphite or amorphous carbon is nucleated on the substrate, it quickly covers the substrate. Accordingly, the synthesis process required many cycles of growth followed by hydrogen etching in order to remove graphite or amorphous carbon, which made growth rate very slow, only a few angstroms per hour. 

However, after the gas activation process such as hot filament or plasma was introduced in the early 1980s, the growth rate of diamond increased abruptly and it became possible to deposit diamond on various substrates. Diamond coated cutting tools for non-ferrous metals, X-ray windows, and heat-sinks are already commercially available these days and intensive researches are being performed on the thin film diamonds for the electronic device applications.




   Surface Microstructure of Diamond Film     
    Raman Spectrum of Diamond Film



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