Influence of working pressure on the field emission properties of carbon nanotubes

High-quality single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and multi-walled carbon nanotubes (MWNTs) with a mean diameter of 6 nm were employed for the measurements of their field emission performance in ultrahigh vacuum conditions.( UHV, 2.0 x 10(-7) Pa) and high vacuum (HV, 1.0 x 10(-4) Pa), respectively. It was found that all the carbon nanotubes (CNTs) showed good field emission stability in UHV, but the stability of SWNTs and DWNTs deteriorated remarkably in HV, while the MWNTs remained stable. On the other hand, it was found that increasing the working pressure within certain limits was in favor of the emission current increase of CNTs. By cycling the working pressure between 2.0 x 10(-7) Pa and 1.3 x 10(-4) Pa, lower vacuum limits of 6.0 x 10(-5) Pa, 1. 0 x 10(-4) Pa and 5.7 x 10(-4) Pa were proposed for the measurements and applications of SWNT, DWNT and MWNT field emitters, respectively.