Double layer-coated carbon nanotubes: Field emission and secondary-electron emission properties under presence of intense electric field

The authors measured the field emission (FE) and secondary-electron emission (SEE) of carbon nanotubes (CNTs) after coating with wide-band-gap materials, such as MgO and CsI. The FE was increased successively after MgO coating and subsequent CsI coating for both single-walled and multiwalled CNTs. SEE also showed the same increase after monolayer and double-layer coating. The field-enhancement factor, β, was calculated from the Fowler–Nordheim equation of FE results, and SEE yield, δ, was measured directly from the SEE measurements, for both monolayer- and double-layer-coated nanotubes. Both values showed similar trends that may be described as follows: (1) The trend for the double-layer-coated CNTs was higher than that for the monolayer-coated CNTs. (2) The trend for the single-walled CNTs was higher than that for the multiwalled CNTs.