Outstanding field emission properties of titanium dioxide /carbon nanotube composite cathodes on 3D nickel foam

Abstract Outstanding field emission properties are achieved for titanium dioxide (TiO 2 ) coated screen-printed carbon nanotubes (CNTs) on a three-dimension (3D) nickel foam (Ni-F) substrate, namely the TiO 2 /CNTs@Ni-F composite cathode. The device exhibits pretty low turn-on field of 0.40 V/μm and threshold field of 0.75 V/μm corresponding with a recorded high field enhancement factor of 27767, and excellent current stability as well as emission uniformity. Based on a comparison study and a proposed model, reasons for the significantly enhanced field emission properties are disclosed. The enhanced edge effect, simultaneously with the reduced field screening effect, arisen by TiO 2 /CNTs micro films and multistage structure of the 3D Ni-F substrate mainly contributes to the lowered operation fields. In addition, the 3D metal substrate provides good adhesion for the TiO 2 /CNTs composite together with the excellent chemical stability of the TiO 2 modifier contributing to the remarkable electrical stability. The high-performance of the TiO 2 /CNTs@Ni-F composite cathode demonstrates potential applications in vacuum electronic devices.