Electron field emission properties of carbon nanotubes grown on iron needles

摘要

Carbon nanotubes (CNTs) were grown on Fe-needle directly by microwave assisted chemical vapor deposition of methane (CH_4). The Fe-needle,when aligned with the electric field of incident microwave, absorbs the microwave efficiently, inducing localized plasma in the vicinity of the tip of Fe-needle. The Fe-needle was heated efficiently, while the deposition chamber was maintained at room temperature. By manipulating the microwave power, layout of Fe-needle, concentration of methane and environmental gases, the CNTs can grow either on the body or tip of the Fe-needle. TEM examination showed that the geometry of the CNTs, straight or bamboo like, varied with the thermal balance around the Fe-needle. Optical emission spectroscopy indicated that the prime factor influencing the growth behavior of the CNTs is the plasma temperature of the gas species. The CNTs can form wherever the supply of carbon species is sufficient and the temperature is suitable. The electron field emission of CNTs-coated Fe-needle can be turned on at approximately 5-6 V/mum applied field and the electrical current density can achieve 500-800 mA/cm~2.