Growth of Diamond Thin Films by dc Plasma Chemical Vapor Deposition and Characteristics of the Plasma

Abstract

Diamond thin films have been formed by dc plasma chemical vapor deposition from a gaseous mixture of methane and hydrogen (gas ratio (CH₄/H₂); 2/100, total gas pressure; 2.66×10⁴ Pa) with a growth rate of ∼20 µm/h. During the course of diamond growth, characteristics of the plasma were measured by the Langmuir single probe method and also by emission spectrometry. From the characterization of the plasma, it was found that the degree of ionization was rather low (∼10^-7), and the statistical temperature of hydrogen gas was ∼5×10³ K. By a thermodynamic investigation at the gas temperature around 5×10³ K, it was revealed that the source gases (H₂ and CH₄) of over 99% are decomposed to neutral atomic hydrogen and atomic carbon.