In situ fabrication of HfC-decorated carbon nanotube yarns and their field-emission properties

HfC-decorated carbon nanotube (CNT) yarns have been fabricated by pre-coating pure CNT yarns with Hf and in situ current heating in vacuum. HfC nanocrystals were formed at about 1600 K through reaction of the CNTs with Hf. The fabricated HfC-CNT yarns had a work function of 3.9 eV, lower than that of pure CNT yarns. For field-emission applications, HfC-CNT sharp tips made up of HfC nanorods were obtained by Joule-heating-induced electrical breakdown above 2100 K. Their emission current could reach 320 μA with a calculated density of 800 A/cm2 at an extraction voltage of 400 V. The emitters could operate under a rough vacuum of 10−2 Pa without obvious degradation. These excellent field-emission properties are attributed to the HfC nanorods, which have a low work function and are resistant to ion bombardment.