Image Number 3 for United States Patent #8070548.
A method for making the thermal electron emitter includes following steps. Providing a carbon nanotube film including a plurality of carbon nanotubes. Treating the carbon nanotube film with a solution comprising of a solvent and compound or a precursor of a compound, wherein the compound and the compound that is the basis of the precursor of a compound has a work function that is lower than the carbon nanotubes. Twisting the treated carbon nanotube film to form a carbon nanotube twisted wire. Drying the carbon nanotube twisted wire. Activating the carbon nanotube twisted wire.