Hydrogen Diluted Methane Plasma Gas–Substrate Metal Interaction

Abstract

The interaction between hydrogen-diluted methane plasma gas and substrate metal has been investigated to evaluate interfacial phenomena in the heteroepitaxial growth and initial-stage growth of diamond by combing chemical vapor deposition and field ion microscopy (CVD–FIM). The interaction with plasma gas was evaluated from the behavior of the Fowler–Nordheim plot and field ion images, after plasma gas was exposed to a tungsten needle specimen (W tip) at methane contents CH4/H2 of 1–3%. The plasma gas–W tip surface interaction was very intensive, and thick carbonaceous layers in the amorphous state were formed with a depth of several tenths atomic layers on the top surface of a W tip. Some condensed carbon clusters consisting of several carbon atoms emerged on the interfacial carbonaceous mixed layers. The energetic carbon atom was very cohesive, and the condensed carbon clusters corresponded to prenucleation or prediamond states prior to bulk diamond growth. The behavior of the field emission characteristics originating from the condensed clusters consisting of carbon atoms was also discussed.