939 research outputs found
Analytical treatment of cold field electron emission from a nanowall emitter
This paper presents an elementary, approximate analytical treatment of cold
field electron emission (CFE) from a classical nanowall. A simple model is used
to bring out some of the basic physics of a class of field emitter where
quantum confinement effects exist transverse to the emitting direction. A
high-level methodology is presented for developing CFE equations more general
than the usual Fowler-Nordheim-type (FN-type) equations, and is applied to the
classical nanowall. If the nanowall is sufficiently thin, then significant
transverse-energy quantization effects occur, and affect the overall form of
theoretical CFE equations; also, the tunnelling barrier shape exhibits
"fall-off" in the local field value with distance from the surface. A conformal
transformation technique is used to derive an analytical expression for the
on-axis tunnelling probability.Comment: 48 pages, 4 figure
Atomic decoration for improving the efficiency of field electron emission of carbon nanotubes
The field electron emission from the single-walled carbon nanotubes with
their open ends terminated by -BH, -NH, and -O has been simulated. The
apex-vacuum barrier and the emission current have been calculated. It has been
found that -BH and -NH suppress the apex-vacuum barrier significantly and lead
to higher emission current in contrast to the -O terminated structure in the
same applied field. The calculated binding energy implies that the carbon
nanotubes terminated with -BH and -NH are more stable than those saturated by
oxygen atoms or by hydrogen atoms.Comment: 8 pages, 9 figures, LaTeX; content changed, typos corrected,
references adde
New Thermal Field Electron Emission Energy Conversion Method
New thermal field electron emission energy conversion method for vacuum electron-optical systems
(EOS) with a nanostructured surface electron sources is offered and developed. Physical and numerical
modeling of an electron emission and transport processes for different EOS is carried out. It is shown that
at the specific configuration of electrostatic and magnetic fields in the EOS offered method permits to
realize energy conversion processes with high efficiency.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3524
Field electron emission from diamond and related films synthesized by plasma enhanced chemical vapor deposition
The focus of this thesis is the study of the field electron emission (FEE) of diamond and related films synthesized by plasma enhanced chemical vapor deposition. The diamond and related films with different morphologies and compositions were prepared in a microwave plasma-enhanced chemical vapor deposition (CVD) reactor and a hot filament CVD reactor. Various analytical techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy were employed to characterize the surface morphology and chemical composition.The influence of surface morphology on the field electron emission property of diamond films was studied. The emission current of well-oriented microcrystalline diamond films is relatively small compared to that of randomly oriented microcrystalline diamond films. Meanwhile, the nanocrystalline diamond film has demonstrated a larger emission current than microcrystalline diamond films. The nanocone structure significantly improves the electron emission current of diamond films due to its strong field enhancement effect.The sp2 phase concentration also has significant influence on the field electron emission property of diamond films. For the diamond films synthesized by gas mixture of hydrogen and methane, their field electron emission properties were enhanced with the increase of methane concentration. The field electron emission enhancement was attributed to the increase of sp2 phase concentration, which increases the electrical conductivity of diamond films. For the diamond films synthesized through graphite etching, the growth rate and nucleation density of diamond films increase significantly with decreasing hydrogen flow rate. The field electron emission properties of the diamond films were also enhanced with the decrease of hydrogen flow rate. The field electron emission enhancement can be also attributed to the increase of the sp2 phase concentration. In addition, the deviation of the experimental Fowler-Nordheim (F-N) plot from a straight line was observed for graphitic nanocone films. The deviation can be mainly attributed to the nonuniform field enhancement factor of the graphitic nanocones. In low macroscopic electric field regions, electrons are emitted mainly from nanocone or nanocones with the largest field enhancement factor, which corresponds to the smallest slope magnitude. With the increase of electric field, nanocones with small field enhancement factors also contribute to the emission current, which results in a reduced average field enhancement factor and therefore a large slope magnitude
- …