97 research outputs found
Coherent field emission image of graphene predicted with a microscopic theory
Electrons in the mono-layer atomic sheet of graphene have a long coherence
length of the order of micrometers. We will show that this coherence is
transmitted into the vacuum via electric field assisted electron emission from
the graphene edge. The emission current density is given analytically. The
parity of the carbon pi-electrons leads to an image whose center is dark as a
result of interference. A dragonfly pattern with a dark body perpendicular to
the edge is predicted for the armchair edge whose emission current density is
vanishing with the mixing angle of the pseudo-spin. The interference pattern
may be observed up to temperatures of thousand Kelvin as evidence of coherent
field emission. Moreover, this phenomenon leads to a novel coherent electron
line source that can produce interference patterns of extended objects with
linear sizes comparable to the length of the graphene edge.Comment: 6 pages, 3 figure
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
Field electron emission characteristic of graphene
The field electron emission current from graphene is calculated analytically
on a semiclassical model. The unique electronic energy band structure of
graphene and the field penetration in the edge from which the electrons emit
have been taken into account. The relation between the effective vacuum barrier
height and the applied field is obtained. The calculated slope of the
Fowler-Nordheim plot of the current-field characteristic is in consistent with
existing experiments.Comment: 18 pages, 5 figures Copyright (2011) American Institute of Physics.
This article may be downloaded for personal use only. Any other use requires
prior permission of the author and the American Institute of Physics. This
article appeared in (J. Appl. Phys. 109 (2011) 044304) and may be found at
(http://link.aip.org/link/?JAP/109/044304
Large-scale fabrication of ordered arrays of microcontainers and the restraint effect on growth of CuO nanowires
Technique has been developed to fabricate ordered arrays of microcontainers. We report that ordered microcontainer arrays of Cu can be fabricated on glass substrate by thin film deposition and self-assembly technology. In addition, CuO nanowires are found to grow only in the inner sides of microcontainers, which verifies the stress growth mechanism of CuO nanowires. High-resolution transmission electron microscopy study reveals that CuO nanowires grow along the [110] direction. Such structure may have potential application in micro-electron sources, which have the self-focused function
Screening effects on field emission from arrays of (5,5) carbon nanotubes: Quantum-mechanical simulation
The simulation of field electron emission from arrays of micrometer-long
open-ended (5, 5) carbon nanotubes is performed in the framework of quantum
theory of many electrons. It is found that the applied external field is
strongly screened when the spacing distance is shorter than the length of the
carbon nanotubes. The optimal spacing distance is two to three times of the
nanotube length, slightly depending on the applied external fields. The
electric screening can be described by a factor that is a exponential function
of the ratio of the spacing distance to the length of the carbon nanotubes. For
a given length, the field enhancement factor decreases sharply as the screening
factor larger than 0.05. The simulation implies that the thickness of the array
should be larger than a value but it does not help the emission much by
increasing the thickness a great deal
Simulation for field emission images of micrometer-long SWCNTs
The electron distribution of open-ended single-walled carbon nanotubes with
chirality indexes (7,0) and (5,5) in the field emission conditions was
calculated via a multi-scaled algorithm. The field emission images were
produced numerically. It was found that the emission patterns change with the
applied macroscopic field. Especially, the symmetry of the emission pattern of
the (7,0) carbon nanotube is breaking in the lower field but the breaking is
less obvious in the higher field. The enlargement factor increases with the
applied macroscopic field.Comment: 8 pages, 4 figure
The Controlled Growth of Long AlN Nanorods and In-situ Investigation on Their Field Emission Properties
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