Diamond Films: Recent Developments in Theory and Practice

Abstract

The diamond films of the early 1980s presented two quite different challenges. First how could this new form of diamond be exploited technically? Second, how could this clearly nonequilibrium generation of diamond be understood and the understanding be used to maximum effect? We shall be discussing the ideas of theory and modeling, and we will show how they have contributed to the interplay of science and technology.The science of diamond films is the art of beating nature in the use of carbon. Theory gives the understanding to improve this art. One way in which we improve on nature is in new geometries: controlled growth over selected surfaces o surface regions. The coverage, defect density, microstructure, and rate of growth are key issues. Another way to beat nature is controlled doping. Could wmake n-type semiconductors or lasers using diamond films? A third direction might be routes to control interfaces. Grai boundaries and the regions between small, misaligned crystals affect thermal properties and electron emission. Difficulties with electrical contacts may limit the use of diamond films as semiconductors or insulators. Substrate-film adhesion can determine tribological performance.If theory is to play a role in controlling film deposition, we need to understand the role of theory itself. Theory can add value at several distinct levels. At the highest level, modeling has the potential to provide a substitute for experiment, especially when information is needed about behavior at extreme conditions. When the phenomena are very fast or very complex, theory can be used to interpret limited experiments. At a more modest level, even simple quantitative models can illustrate the many processes occurring during film growth. Atomistic theories of this type can identify the rate-determining steps and point to ways of influencing them. Mesoscopic theories, especially combined with macroscopic approaches like elasticity theory, can identify routes to improved performance.