Influence of Methane Concentration on Crystal Growing Process in CVD Free Standing Diamond Films

The Macro-texture, grain boundary distribution and surface morphlolgy in CVD free standing diamond films deposited with different methane concentrations were observed by X ray diffraction technology, electron backscatter diffraction and SEM. The crystal growing process of {100} and {111} planes in diamond crystal was studied. It is shown that diamond films adsorb activated radical CH2 2-on {100} plane or adsorb CH3- and CH3- on {111} plane alternately. Carbon atoms stack on the film surface during dehydrogenation. At low methane concentration, the expansion ratio of {111} planes is close to, but faster than that of {100} planes because of their relative lower surface energy. The enhanced driving force induced by the increased methane concentration results in faster growth of {100} plane than that of {111} plane, which promotes the formation of {100} texture. The film surface morphology consisits of the exposured {100} planes that are parallel to the film surface and the exposured {111} planes area as the side surface that decrease during the competition growth, which is different from that of single crystal growth.