Characterizations of the dc discharge plasma during chemical vapor deposition for diamond growth

Abstract

During the course of diamond growth by dc plasma chemical vapor deposition, characteristics of the plasma have been measured by means of the Langmuir single probe method and emission spectrometry. For the source gas system of hydrogen and methane (gas ratio: CH4/H2=2/100, total gas pressure: 2.66×104 Pa), it is revealed that the statistical temperatures of hydrogen atoms and electrons in the positive column of the plasma are obtained to be 4.8×103–5.3×103 K and 1×105–1.1×105 K, respectively. The amount of ionized species is fairly small. By calculating the equilibrium constant of gas molecules in these gas temperature ranges, it is found that molecules over 99% H2 and CH4 are decomposed to the neutral H and C atoms.