“…[1][2][3] Recently, carbon nanomaterials such as nanometer-sized crystalline diamond ͑nanodiamond͒, carbon nanotube, carbon nanofiber, and carbon nanowall ͑CNW͒ have been intensively investigated, the results of which have shown that as an excellent electron emitter, they should have large aspect ratio, low-threshold voltage, higher emission current density, and stable emission. [1][2][3] Recently, carbon nanomaterials such as nanometer-sized crystalline diamond ͑nanodiamond͒, carbon nanotube, carbon nanofiber, and carbon nanowall ͑CNW͒ have been intensively investigated, the results of which have shown that as an excellent electron emitter, they should have large aspect ratio, low-threshold voltage, higher emission current density, and stable emission.…”