Secondary electron emission yields from MgO deposited on carbon nanotubes

Abstract

Enormously high secondary electron emission yields under electric field are observed from MgO deposited on carbon nanotubes. The yields reach a value as high as 15 000 and are strongly dependent upon the bias voltage applied to the sample. The creation of the electric field across the MgO film after bombardment of primary electrons is considered as one of key features, since positive charges are generated at the surface by departure of secondary electrons. Subsequent bombarding electrons produce other secondary electrons inside the MgO film, then the liberated secondaries are accelerated towards the surface under the strong field. Under this condition, the secondary electrons gain sufficient energy to create further electrons by impact ionization. The process continues until an equilibrium avalanche is established. To elucidate the earlier explanations, the kinetic energy spectra of secondary electrons are measured by an energy analyzer at various bias voltages in MgO/carbon nanotube samples. The analysis of spectral results with the energy band diagram gives us strong evidence for the suggested mechanism.

Rf Gun with High-Current Density Field Emission Cathode

“…When incident electrons from the electron emitters strike the internal walls of the channel, secondary electrons are emitted from the surface. The FIU team and its collaborators have already observed that the secondary electron emission (SEE) yield increased enormously when electrons bombarded a very thin (~15-30 nm) MgO film deposited on highly conductive carbon nanotube surface [3]. The SEE yield as a function of the bias potential shows the emission yield can be as large as 15,000 secondary electrons per incident primary.…”

“…It is planned to first coat the inside surface of the channel wall with highly conductive material layer (such as electrodeless plated or sputtered Cu [3,4]), as shown in Fig. 3.…”

“…Niobium (Nb) thin films with a thickness of 200 nm were deposited on SiO 2 /Si substrate by DC magnetron sputtering. Catalyst solution was prepared with iron (III) nitrate nonahydrate (Fe(NO 3 ) 3 •9H 2 O,40mg), bis(acetylacetonato)-dioxomolybdenum (VI) (MoO 2 (acac) 2 , 3mg), Fe:Mo molar ratio was about 10:1. And aluminum oxide nanoparticles (30, 15, and 7.5 mg) were used as catalyst supporter.…”

“…Sharp tips with high aspect ratio can help electrons to tunnel through the barrier. Since single-wall carbon nanotubes (SWNTs) have high aspect ratio and small radius of curvature (~ 1 nm), they have been reported to show large field enhancement factor, low threshold voltage, and high emission current [3]. However, the degradation of emission current with time is an obstacle for the application of SWNTs as field emitters [4].…”

Preparation of single-walled carbon nanotube reinforced magnesia films

“…Magnesia layers has been increasingly noted for their advantages as a key element of plasma display panels (PDPs) [1][2][3][4][5]. It protects the dielectric layer above the electrodes from sputtering while yielding a high ion-induced secondary electron emission (SEE) coefficient.…”