The role of the substrate surface area/reactor volume ratio in chemistry and kinetics of chemical vapor deposition

Chemical vapor deposition of carbon from methane was used as a test reaction to investigate the influence of the substrate surface area/reactor volume ratio, [AR/VR], on the deposition kinetics. Experiments were performed at an ambient pressure of about 100 kPa and a temperature of 1100 °C using methane at a partial pressure of 10 kPa and a methane/hydrogen mixture (PCH4=17.5kPa, PH2=2.5kPa). The [AS/VR]-ratio was varied from 1.8 to 10, 20, 40 and 80 cm-1. It is shown that surface related deposition rates are not constant, but decrease with increasing [AS/VR-ratio. This result indicates that any kinetics can be determined by changing this ratio, which is called the third parameter of CVD. Consequences are discussed