Effect of CO₂ Addition on Preparation of Diamond Films by Direct-Current Hot-Cathode Plasma Chemical Vapor Deposition Method

Diamond films are deposited on Mo substrates by dc hot-cathode plasma chemical vapor deposition method using a CH₄-H₂-CO₂ gas mixture. Adjusting the flow of CO₂, we study the relevant influence on surface morphology, grain orientation and crystalline quality of films with scanning electron microscopy, x-ray diffraction, Raman spectroscopy, respectively. The results show that grain orientation of the films has a transition with the increasing CO₂ addition, from (100) orientation to (110) orientation and then (111) orientation. The crystalline quality is improved but the growth rate is decreased by raising the flow of CO₂. The experimental results are also discussed briefly.