Solid–vapor phase boundary of carbon at low temperature and low pressure

Abstract

We have investigated the thermal equilibrium phase diagram of carbon in a condition of low temperature and low pressure which is relevant to diamond film growth from vapor phase. All the molecules in a chamber of a finite volume are assumed to be fully activated and decomposed into single atoms so that the system may be considered as a mixture of carbon vapor and atomic hydrogen gas equilibrated with a solid phase of carbon. By calculating the carbon chemical potentials for both solid and gas phase, sublimation curve in the presence of partial pressure of atomic hydrogen gas has been obtained. The phase boundary of the equilibrium vapor pressure turns out to be a lower limit of recent many studies on diamond film growth by chemical vapor deposition method.