A cathode of an electron emitting device is described, where the cathode comprises a carbon nanotube (CNT); a nano-filler material; and a carbonizable polymer, and where the cathode exhibits increased hardness, is formed by high temperature thermal treatment, and is devoid of a substrate. Also described is a method of forming a cathode of an electron emitting device, where the method comprises a) forming a dispersed mixture comprising a carbon nanotube, a nano-filler material, and a carbonizable polymer in a solvent; b) coating and/or extruding the mixture; c) drying the coated and/or extruded mixture to remove at least a substantial portion of the solvent; and d) subjecting the dried mixture to a high temperature thermal treatment; where the method results in the cathode of an electron emitting device having increased hardness.

A composite carbon nanotube structure comprises a first carbon nanotube structure and a second carbon nanotube structure. The first carbon nanotube structure includes a number of first carbon nanotubes extending substantially along the same direction and joined end-to-end by van der Waals force. The second carbon nanotube structure includes a number of second carbon nanotubes extending from a surface of the first carbon nanotube structure.

A cathode of an electron emitting device is described, where the cathode comprises a carbon nanotube (CNT); a nano-filler material; and a carbonizable polymer; and where the cathode exhibits increased hardness, is formed by high temperature thermal treatment, and is devoid of a substrate. Also described is a method of forming a cathode of an electron emitting device, where the method comprises a) forming a dispersed mixture comprising a carbon nanotube, a nano-filler material, and a carbonizable polymer in a solvent; b) coating and/or extruding the mixture; c) drying the coated and/or extruded mixture to remove at least a substantial portion of the solvent; and d) subjecting the dried mixture to a high temperature thermal treatment; where the method results in the cathode of an electron emitting device having increased hardness.