Abstract

If diamond deposits and graphite etches simultaneously in the low pressure synthesis of diamond, the chemical potential of carbon in diamond and in graphite would be, respectively, lower and higher than that in the gas phase. The analysis leads to diamond being more stable than graphite, contradicting the well-established stability between diamond and graphite. In the C-H system, the solubility of carbon in the gas phase is minimum at ≈ 1500 K and it increases with decreasing temperature. In the charged cluster model, diamond nucleates in the gas phase. The gas phase, being depleted of carbon by the maximum precipitation of the diamond clusters at ≈ 1500 K, becomes undersaturated with carbon when supercooled to the substrate temperature and a portion of the cluster is expected to etch. The unetched portion of the diamond cluster will deposit with simultaneous etching on an atomic scale. Thus, diamond deposition with simultaneous graphite etching can be explained based on the charged cluster model without leading to the thermodynamic paradox.

© 1995 Optical Society of America