Field electron emission from nanotube carbon layers grown by CVD process

We present the field emission characteristics of nanotube carbon layers grown by chemical vapor deposition process. In this process, products of thermal decomposition of polyethylene were used as the source of carbon. SEM and HREM investigations of manufactured layers showed that these layers consisted of randomly oriented conical layer carbon nanotubes (CLNTs). The diameter of nanotubes usually ranged from 20 up to 40 nm. The investigations of field electron emission were fulfilled at room and low (≈120 K) temperatures. The emission current of 0.1 nA arose at the average electric field Eav=1.5–2.5 V/μm. The emission current of 100 μA (current density ≈10 mA/cm2) was observed at Eav=4–4.5 V/μm. The value of field amplification coefficient β was equal to 1300–2000. The field emission characteristics replotted in Fowler–Nordheim coordinates were linear at room and low (≈120 K) temperatures for current variation of 5–6 orders of magnitude. The calculations of field amplification coefficient β were fulfilled for an array of aligned closed nanotubes. These calculations demonstrated strong dependence of β versus the distance between nanotubes and their height.