Synthesis of double-walled carbon nanotube films and their field emission properties

Continuous double-walled carbon nanotube (DWCNT) films were synthesized using an Fe–Mo catalyst by the arc discharge method. This new catalyst has dramatically improved the purity and selectivity of DWCNT product. High-resolution transmission electron microscopy indicates that the outer and inner diameter of DWCNT are 1.9–4.7 nm and 1.2–3.8 nm, respectively. The field emission properties of DWCNT films have been studied. The directly grown film was transferred onto quartz substrates and used as emission cathodes, and has demonstrated a quite good emission performance. Moreover, the emissions of DWCNT films have been further improved by heat treatment. The film after 400 °C oxidation shows excellent field emission property with a low turn-on (Eto = 0.6 V/μm) and threshold field (Eth = 0.9 V/μm) corresponding to the emission current density of 1 μA/cm2 and 1 mA/cm2, respectively.