Investigations On The Controllable Synthesis Of N-Doped Carbon Nanotubes Based Metal Substrate And The Performances Of The Cathodes

Nitrogen-doped carbon nanotubes?NCNTs?are expected to be widely used in vacuum microelectronic devices due to its high electrical conductivity,low work function,and large aspect ratio,but the low cost and strongly attached NCNT electrodes are still insufficient in current situation.In this paper,NCNTs were grown directly on the stainless steel substrate by chemical vapor deposition?CVD?method at atmospheric pressure.Meanwhile,the adhesion between the substrates and NCNTs and the surface resistance of NCNT electrodes were measured.Finally,the field emission?FE?performances of NCNT electrodes were tested using a two-stage configuration.?1?In this paper,the stainless steel substrates were first anodized by oxalic acid solution?3.0 mol/L?,then NCNTs were grown directly on the stainless steel substrates by CVD method at atmospheric pressure using ammonia and acetylene as the precursors and argon as the protecting gas.As a contrast,we used acetylene as a precursor and argon as a protective gas,carbon nanotubes?CNTs?were grown directly on the stainless steel substrates.?2?The as-prepared products were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Raman spectroscopy?Raman?and X ray diffraction energy dispersive spectrometer?XPS?.The results show that:it can be seen from SEM and TEM images,the diameter of NCNTs becomes more large and the surface is more smooth than those of CNTs.Raman tests show that both CNTs and NCNTs have good crystal structure?I_G/I_D>1?.However,in comparison with CNTs,the I_G/I_D of NCNTs decreases slightly,mainly due to the N doped CNTs.In addition,by XPS characterization,in addition to the C element,the NCNT sample also contains N elements and is dominant by graphite nitrogen.?3?The adhesive force,surface resistance and FE performances of the products are tested.The results show that:the maximum adhesion of NCNTs increases from 8.04 N to12.06 N due to the anodization treatment.After N doping CNTs,the surface resistance of CNT decreases from 5.801?to 1.709?and the turn on field of CNT is reduced from 3.26 V/?m to 1.61 V/?m.The current density?²3 mA/cm²?of CNTs is completely attenuated after 7 hours operation during FE process,while the current density?²3 mA/cm²?of NCNTs decayed by 20%over 40 hours under the pressure of¹0^-4 Pa.