CARBON NANO-TUBES - THEIR FORMATION PROCESS AND OBSERVATION BY ELECTRON-MICROSCOPY

Carbon nano-tubes have been investigated thoroughly by transmission electron microscopy. Non-helical tubes are not exceptional and mixing with helical tubes with various helicities is often observed within the same tubule. The helical nature of the tubes is thought to be actually required by lattice continuity during the formation of successive seamless concentric tubes. Besides, introducing dislocations is also a possible accommodation mechanism for the strains produced between the successive tube surfaces. Reciprocal space constructions have been accomplished for explaining the diffraction effects for non-helical tubes as well as for helical ones. Well-resolved high-resolution images are obtained in particular for the non-helical tubes and the image features could be confirmed by computer simulations. A possible growth process for the successive concentric tubes is proposed.