A review of Schottky and cold field-emission cathode characteristics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100172425 ◽

1994 ◽

Vol 52 ◽

pp. 938-939

Author(s):

L. W. Swanson

Keyword(s):

Field Strength ◽

Field Emission ◽

Full Width ◽

Half Maximum ◽

Continuous Change ◽

Field Emission Cathode ◽

High Brightness ◽

Surface Electric Field ◽

Electron Focusing ◽

Emission Cathode

Two high brightness, point cathodes currently being used in TEM's and nanometer electron focusing systems are the cold field emission (CFE) and Schottky emission (SE) cathodes. In terms of emission mechanisms, CFE and SE represent two extremes of a continuous change in surface electric field strength F and temperature T of a pointed cathode of work function ϕ. The conditions for CFE and SE emission modes can be stated as follows:CFE: 4π(2mϕ(1/2 kT/heF < 0.5SE: he1/4F3/42<2m1/2 < 0.5When the above conditions are met most electrons are tunnelling from at or near the Fermi level inthe case of CFE and thermally excited over the vacuum barrier in the case of SE. The expressions for the current density J are:CFE: JCFE = a(F2/ϕ)exp(10.4/ϕ1/2)exp(-bϕ3/2/F)(A/cm2SE: JSE = 1202exp(-(ϕ - 3.8F1/2)/)kT)(A/cm2)where a = 1.54×10-6, b = 0.644 and F and ϕ are in units of V/Å and eV respectively.One important aspect for source optics applications is the energy spread of the emitted electrons for the two emission regimes. Fig. 1 gives the theoretical values of the full width at half maximum (FWHM) of the energy distribution for the case of CFE with ϕ = 4.0 eV, T = 300 K, J = 1×105 A/cm2 and SE with ϕ = 3.0 eV, T = 1800, J = 1×103 A/cm2.

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High Brightness Electron Gun Using a Field Emission Cathode

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101219 ◽

1968 ◽

Vol 26 ◽

pp. 294-295

Author(s):

A. N. Broers

Keyword(s):

Field Emission ◽

Electron Gun ◽

Field Emission Cathode ◽

High Brightness ◽

Probe Size ◽

Test Grid ◽

Two Stages ◽

Emission Cathode ◽

Scanning Electron ◽

Better Than

A field emission cathode electron gun with two stages of acceleration has been built in order to measure the electron beam brightness that can be produced in practice from a tungsten field emission cathode. The gun is similar to that reported by A. Crewe except that the accelerating electrodes are plane, rather than shaped, apertures, and the cathode is located by a gimbal mechanism which allows the cathode to be tilted over an arc of 70° in any direction and positioned laterally. The gun electrodes have been precisely machined with the apertures round within 0.25 micron and aligned with respect to each other to better than 10 micron. The second accelerating electrode is followed by scan plates, a test grid, and an electron detector which together allow the probe size to be measured in the usual scanning electron microscope mode.

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Modelling of the Influence of a Pointed Field Emission Cathode Design from the Silicon Carbide with Graphene Film on the Electric Field Strength

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.752-753.163 ◽

2015 ◽

Vol 752-753 ◽

pp. 163-167 ◽

Cited By ~ 4

Author(s):

Alexander M. Svetlichnyi ◽

Oleg. A. Ageev ◽

Evgeny Yu. Volkov ◽

Igor L. Jityaev ◽

Maxim V. Dem'yanenko

Keyword(s):

Silicon Carbide ◽

Field Strength ◽

Electric Field ◽

Electric Field Strength ◽

Field Emission ◽

Graphene Film ◽

Field Emission Cathode ◽

Interelectrode Gap ◽

Half Angle ◽

Emission Cathode

Graphene film on silicon carbide is considered to be promising material for high-frequency vacuum nanoelectronics. However, the possibility of graphene application in this area is still poorly understood. We have carried out the simulation of the electric field distribution in interelectrode gap of the anode-cathode system pointed field emission cathode based on silicon carbide with graphene film on its surface subject to the rounding-off radius of the top, interelectrode gap, height and cathode forming half-angle of the cone opening by the finite element method. The influence of constructional parameters on the electric field strength in the test structure was analyzed. It is shown that the values of rounding-off radius of the cone point and interelectrode distance has the biggest influence on the electric field in the investigated structure. Changing of the height and cathode forming half-angle of the cone opening does not lead to a significant increase or decrease of the electric field value.

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