Development of high stable carbon nanotube field emitters against vacuum breakdown for miniature X-ray tube

Abstract

Carbon nanotube (CNT) is considered among the most promising materials for field emission due to their high aspect ratio, exceptional mechanical strength, high thermal and electrical conductivities; and good chemical resistance. CNT is being used in various areas such as field emission display (FED), high-resolution electron beam instruments, and miniature X-ray devices due to its aforementioned outstanding properties. In spite of such superb characteristics, the realization of CNT emitter has been limited due to the stability issues of the CNT emitters during field emission, such as destruction of the CNT emitters by sputtering, excessive joule heating, residual gases, and vacuum breakdown. The critical issue nowadays in the development of CNT emitters is to find a method to solve the problem related to the destruction of the CNT emitters due to the arcing, which is an inevitable factor in the field emis-sion at high electric field. Furthermore, the breakdown event is likely to be an irreversible process and is cata-strophic from both the operational and financial point of view, because it might severely damage the emitter (cathode). So the future performance of the CNT emitter will almost certainly be permanently impaired. To overcome the problem related to vacuum breakdown, high stable carbon nanotube (CNT) emitters that can endure intense arcing (vacuum breakdown) have been developed. The CNT emitters/cathodes are fabricated on the flat copper tip using metal binders (a mixture of silver, copper and indium) at relatively high temperature (900 ˚C). During electrical treatment based on vacuum breakdown and electrostatic force, field emission properties and the morphologies of the CNT emitters were remarkably improved and the data were recorded. The CNT emitters show remarkable stability against vacuum breakdowns after electrical treatment due to the strong adhesion with substrate as a result of good wettability of the metal binders. The degree of uniformity...