Thin film diamond by chemical vapour deposition methods

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Abstract
Diamond, the sp3-bonded allotrope of carbon, has long held a special place in the hearts and minds both of scientists and the public at large. For the latter, the word diamond may conjure up images of 57 facetted brilliant gem stones, Amsterdam or mines in South Africa, wealth and special occasions. To the scientist, diamond is impressive because of its wide range of extreme properties. As Table 1 shows, by most measures diamond is'the biggest and best': It is the hardest known material, has the lowest coefficient of thermal expansion, is chemically inert and wear resistant, offers low friction, has high thermal conductivity, is electrically insulating and optically transparent from the ultra-violet (UV) to the far infrared (IR). Given these many notable properties, it should come as no surprise to learn that diamond already finds use in many diverse applications including, of course, its use as a precious gem, but also as a heat sink, as an abrasive, and as inserts and/or wear-resistant coatings for cutting tools. Obviously, given its many unique properties it is possible to envisage many other potential applications for diamond as an engineering material, but progress in implement-ing many such ideas has been hampered by the comparative scarcity of natural diamond. Hence the long running quest for routes to synthesize diamond in the laboratory. At ambient temperatures and pressures graphite is the stable form of solid carbon. Its enthalpy of formation is a mere 2.9 kJ mol-lower than that of diamond, but a large activation barrier rules out simple thermal activation as a means of driving the graphite + diamond interconversion. The activation energy for graphitization at the { 1 10) diamond surface has been measured

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