Cathodic vacuum arc plasma with graphite or graphite-metal composite cathode was ignited under medium vacuum filled with helium gas. The craters of cathode spots and their vicinities were observed using a high-resolution scanning electron microscope. Multiwall carbon nanotubes and nanocapsules were observed at the cathode spot crater. The nanotubes were further observed using a high-resolution transmission electron microscope.
The Institute of Electrical Engineers of Japan