金刚石低压气相生长的驱动力

DRIVING FORCE FOR DIAMOND GROWTH IN LOW PRESSURE VAPOR PHASE

以CH4／H2体系为例，研究了气相生长金刚石和石墨的驱动力随温度和CH4的摩尔分数的变化情况若不考虑超平衡氢原子的作用，则石墨的生长驱动力总是大于金刚石的生长驱动力；如考虑超平衡氢原子的作用，则在一定的温度和CH4摩尔分数条件下，生长金刚石的驱动力将大于零且生长石墨的驱动力小于零。结果表明，此时气相中碳的化学势高于金刚石的化学势而低于石墨的化学势因此，气相中将只生长金刚石而不生长石墨，甚至出现金刚石生长的同时石墨被腐蚀的现象。

Driving forces for diamond and graphite growth in CH4/H2 mixtures are calculated in consideration of activated effect of super-equilibrium atom hydrogen on graphite under 4.8 kPa pressure. The driving force for diamond growth is positive with simultaneous negative driving force for graphite in the suitable ranges of temperature and mole fraction of CH4. The result indicates that the chemical potential of carbon in the vapor phase is higher than that in diamond and lower than that in graphite simultaneously. So diamond is deposited without graphite co-deposition, and the preexisting graphite will be etched during diamond deposition process.