▎ 摘　　要

NOVELTY - The carbon nano tube is obtained by doping outer side of a graphene sheet with one or more kinds of carbon substances. USE - For field emission-type cold cathode electron-emitting element for display device (claimed). ADVANTAGE - Electron emission efficiency of the cathode is improved. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (1) carbon nano tube aggregate comprising several carbon nano tubes in which carbon substances are doped in its outer or inner side; (2) field emission-type cold cathode electron-emitting element obtained using carbon nano tube aggregate; (3) doping method which is performed using a gaseous doping substance; and (4) manufacture of field emission-type cathode element which involves doping carbon nano tube or its aggregate and oscillating the substrate of the element in which the aggregate is maintained.