Comparison of field and thermionic emissions from carbon nanotubes

Abstract

The electron emission from single-wall carbon nanotubes (SWCN) is investigated theoretically by using the tunnelling theory with the tight-binding approach. We compare the electron emission from SWCN in different temperatures and electric fields. In the normal condition, T < 1000 K and 2 V nm−1 < F < 8 V nm−1, the field electron emission (FEE) dominates the electron emission process, which follows approximately the Fowler–Nordheim behaviour. The multi peaks of the FEE energy distribution occur near the Fermi level. At high temperature T ⩾ 1000 K the FEE current is larger than that of the thermionic electron emission (TEE) current in F < 6 V nm−1 but smaller for F > 6 V nm−1. A minimum of the fractional TEE current occurs at the electric field, 5–6 V nm−1 minimum. This is because the strong electric field suppresses both the width and the height of the vacuum potential barrier, which leads to a competition between the FEE and the TEE current.