Abstract
Carbon nanotubes are usually found inside the carbon deposit, which grows on the cathode of dc carbon-arc rod, as fibers or whiskers with co-existing carbon nanoparticles. Curled and intertwined carbon nanotubes having random orientation were also found on the top surface of the columnar carbon deposit, which has a sootlike color. The growth of carbon nanotubes at the top surface of the columnar deposit suggests that carbon nanotubes are formed on the top surface and restored as a columnar deposit.