Synchrotron X-ray photoelectron spectroscopy and field emission of double-walled carbon nanotubes – Dependence on growth temperature

Double-walled carbon nanotubes (DWCNTs) were synthesized by using thermal chemical vapor deposition on MgO-supported Fe–Mo catalysts, in the temperature range 800–1000 °C. Outer diameters were 1.5–2 nm at all growth temperatures. As growth temperature was increased, C1s peaks of X-ray photoelectron spectroscopy became broader and valence band intensity increased due to stronger van der Waals interaction between DWCNTs induced by higher crystallinities. Field emission from the as-grown DWCNTs exhibited a large current density enhancement with increasing growth temperature.