Physical and magnetic characteristics of carbon nanotubes radiated by proton beams

Abstract

Single-walled carbon nanotubes were radiated by proton beams with energy of 35.7 MeV at the Bragg peaks, and magnetic force gradient images and topography were simultaneously measured by using a Nanoscope IV scanning probe microscope while changing the tip distance from the sample. The results show that the magnetic force gradient images become unclear as the scan height increases from 10 nm from the surface of the specimen and completely disappear at 50 nm. When the CNTs were radiated by proton beams, however, clear magnetic force gradient images were observed even at higher scan heights (100 nm) while very little change was noticed in the physical properties, including the tube shapes. It is interesting to note that magnetic force gradient images were not changed by reversing the magnetization of the tip, which reflects an induction of magnetism on the carbon nanotubes.