An electron gun includes a plate-like main cathode 77 having an electron emitting surface 79 and a sub-cathode 81 provided toward the rear surface of the main cathode to heat the main cathode 77 by imparting an electron bombardment. Exemplary nano-particles are selected from the group consisting of particulate nano-silica, nano-alumina, nano-zinc oxide, nano-boron, nano-iron oxide, and combinations thereof. The side mounted rollers will allow the blade to move upwards and downwards on the tracks. According to one embodiment, the conductive gate dielectric can contain doped hafnium zirconium nitride or doped hafnium zirconium oxynitride.