Carbon Nanocoils Synthesized On Stainless Steel Substrates And Their Field Emission

carbon nanocoils(CNCs) have unique three-dimensional spiral structure, compared with the carbon nanotubes(CNTs). They have more excellent mechanical and electromagnetic properties. So they can be used in field-emission devices, electromagnetic wave absorption film, nano-spring, etc. At present, people have widely studied the synthesis of CNCs, and using the low-cost substrates to synthesize CNCs is a big hot spot. This paper has studied the CNCs synthesized on the ordinary stainless steel(SS), their growth mechanism and their field-emission properties.Firstly, we have successfully and largely synthesized CNCs using the Sn-coated SS substrates by a thermal chemical vapor deposition (CVD) method. The result shows that the Sn-coated SS after calcination at900℃is most beneficial for synthesizing the CNCs. By studying the morphologies of the pure and the Sn-coated SS substrates after calcinations at700-900℃, it is considered that the calcination leads to the crazing of SS substrate surface, which makes Fe (Ni) and Sn fully mixed and forms active Fe(Ni)-Sn-O catalyst particles suitable for the growth of CNCs, at900℃. The Raman spectrums of the deposits synthesized on the Sn-coated SS substrates, which were pretreated at700-900℃, show that there are many structural defects in the deposits, which are mainly carbon nanofibers(CNFs) and CNCs.Secondly, we have studied the field-emission properties of the grown CNCs dispersed on an n-type Si substrate. The result shows that the CNCs have lower average turn-on electric field strength of1.6V/μm. We also have simulated the electric fields on a stand-up and a laid-down carbon nanocoil(CNC) and a laid-down nanotube(CNT) using a finite element method. It is found that the distribution of electric fields on a stand-up and a laid-down CNC successfully explain the behavior of the F-N plot. It is also found that the field enhancement factor β for the laid-down CNC is2.26times larger than that for the laid-down CNT. This is because that the helical morphology of CNC can reduce the screen-effect produced by the surrounding substrate. In this case, CNCs can more easily emit electrons, which are promising to be used in X-ray sources, field emission displays and other micro-or nano-devices.