THEORETICAL ASPECTS FOR LOW-PRESSURE DIAMOND SYNTHESES

Low pressure diamond syntheses had seemed thermodynamically impossible . Now diamond syntheses under low pressures is very easy. However, the development of the theoretical aspects was rather slow. A chemical pu mp model, proposed previously by one of the authors, J.-T. Wang, toget her with J.-O. Carlsson, gives explanations about the thermodynamics a nd mechanisms of chemical vapor deposition diamond syntheses under low pressures. Based on the chemical pump model carbon atoms are pumped b y excited chemical particles (such as super-equilibrium hydrogen atoms ) from the stable graphite phase to the metastable diamond phase. Seve ral sets of chemical pump reactions (thermodynamically coupled reactio ns) for diamond growth are described in this paper. In spite of the im portance of thermodynamic coupled reactions in biochemistry, low press ure diamond syntheses are important developments in ordinary chemistry . Influences of the chemical pump effect on the gas phase are also dis cussed in this paper. Theoretical calculated results and predictions a gree with the experimental observations.