Diamond Synthesis by the Microwave Plasma Chemical Vapor Deposition Method Using the Pretreated Carbon Dioxide and Hydrogen Mixed-Gas System

Abstract

High-quality diamond was obtained by the microwave plasma-assisted chemical vapor deposition (plasma CVD) method using the pretreated carbon dioxide (CO2) and hydrogen (H2) mixed-gas system. The pretreatment method is as follows: at first, CO2 and H2 pass through the prereactor, where plasma is generated by microwave discharge, and then the reactant passes through the cold trap at around 185 K in order to remove water (H2O) produced in the plasma from CO2 and H2. The residue of the pretreated CO2 and H2 mixed gas, which consists of CO, CO2 and H2, is introduced into the main reactor where diamond is synthesized. Diamond can grow to a feed ratio of CO2/H2=25/100 sccm. Plasma diagnosis was performed using optical emission spectroscopy (OES) and gas chromatography (GC).