Electron field emission characteristics of nano-carbon needle films fabricated by microwave plasma CVD

In this work, nano-carbon needle films (NCNFs) were prepared on p-type Si (100) substrates by means of quartz-tube type microwave plasma chemical vapor deposition (MWPCVD) in a hydrogen and methane mixture. The influences of total gas pressure on the nano-needle structure of carbon films were studied by field emission scanning electron microscope (FESEM). The field emission (FE) test indicated that the threshold electric field of NCNFs was reduced and the highest emission current density at an electric field of 5 V/µm was increased with increasing the total gas pressure. The good field emission properties with a low threshold field of 2.3 V/µm and a highest current density of 128.6 mA/cm
²
were obtained from NCNFs deposited at the total gas pressure of 60 Torr. A modified F-N model considering statistic effects of FE tip structures was proposed and the FE data in the low E region were reasonably interpreted.