W(310) cold-field emission characteristics reflecting the vacuum states of an extreme high vacuum electron gun

2013 ◽  
Vol 84 (1) ◽  
pp. 013305 ◽  
Author(s):  
Boklae Cho ◽  
Kokubo Shigeru ◽  
Chuhei Oshima
Keyword(s):  
Field Emission ◽  
High Vacuum ◽  
Electron Gun ◽  
Emission Characteristics ◽  
Vacuum States

Energy Filtering of Schottky Field Emission Gun Using Fringe Field Monochromator

1999 ◽  
Vol 5 (S2) ◽  
pp. 646-647
Author(s):  
H.W. Mook ◽  
A.H.V. van Veen ◽  
P. Kruit
Keyword(s):  
Field Emission ◽  
Low Voltage ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Gun ◽  
Fringe Field ◽  
Objective Lens ◽  
Electronic Band ◽  
Energy Width ◽  
Energy Filtering

The energy resolution which can be attained in electron energy loss spectroscopy (EELS) is determined by the energy spread of the electron source. The energy width of a high brightness electron gun (typically 0.4 to 0.8 eV) blurs the energy spectrum. A pre-specimen energy filter or monochromator must be used to reduce the energy width of the beam below 0.1 eV to allow detailed EELS analysis of the electronic band structures in materials. The monochromator can not only improve EELS, but it is also capable of improving the spatial resolution in low voltage SEM, which is limited by the chromatic blur of the objective lens. A new type of monochromator the Fringe Field Monochromator has been designed and experiments in an ultra high vacuum setup show the monochromatisation of a Schottky Field Emission Gun.

Development of Field-Emission Gun for High-Voltage Electron Microscope

1990 ◽  
Vol 48 (2) ◽  
pp. 94-95
Author(s):  
T. Tomita ◽  
S. Katoh ◽  
H. Kitajima ◽  
Y. Kokubo ◽  
Y. Ishida
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Field Emission ◽  
High Voltage ◽  
High Vacuum ◽  
Electron Gun ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Acceleration Tube

It is well known that the combination of a field emission gun (FEG) and a conventional transmission electron microscope (CTEM) is extremely important for nanometer area analysis in analytical electron microscopy. However, the smaller illumination angle and reduced energy spread of FEG than those of a conventional electron gun (W hair pin filament or LaB6) give a slowly damping envelop function in phase contrast transfer function (PCTF). Thus the FEG ensures application not only to analytical microscopy but also to high resolution electron microscopy to improve the information limit.In a high voltage electron microscope (above 200 kV), high-speed vacuum pumps have to be provided below the acceleration tube to get an ultra high vacuum (UHV) around the field emission tip located at the top of the acceleration tube. However, this method is not always the best way to provide UHV because of the poor vacuum conductance caused by the electrodes inside the acceleration tube.

A low-voltage field-emission column with a Schottky emitter

1984 ◽  
Vol 42 ◽  
pp. 454-457
Author(s):  
D.W. Tuggle ◽  
S.G. Watson
Keyword(s):  
Field Emission ◽  
Low Voltage ◽  
High Current Density ◽  
High Vacuum ◽  
Energy Spread ◽  
Electron Gun ◽  
Emission Current ◽  
High Current ◽  
Field Mode ◽  
Over The Top

The advantages of a room-temperature field emission (FE) cathode for forming a sub-micrometer high current, low voltage electron probe, namely small energy spread, high brightness and a small virtual source diameter are somewhat offset by the high vacuum required in the electron gun and the fluctuations in the emission current. The thermal-field mode of operation, with its relaxed vacuum requirements and relatively stable emission current has the disadvantage of an increased energy spread of emission, which degrades the spatial resolution of a focused beam. A Schottky point emitter, similar in geometry to a field emitter but with a larger radius, can achieve high current density by use of a low work function surface operating at elevated temperature. In the Schottky emission (SE) mode, electron transmission over the top of the potential barrier rather than tunneling through the barrier is the emission mechanism.

A study on the field emission properties of Bi2Se3 nanostructures prepared by laser ablation

2019 ◽  
Vol 33 (14n15) ◽  
pp. 1940050
Author(s):  
Yu Ohsumi ◽  
Pankaj Koinkar ◽  
Akihiro Furube ◽  
Keh Moh Lin ◽  
Subhash Kondawar ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Field Emission ◽  
Direct Method ◽  
High Vacuum ◽  
Target Material ◽  
Ultra High Vacuum ◽  
Emission Characteristics ◽  
X Ray ◽  
Emission Properties ◽  
Field Emission Properties

One of the effective methods known as pulse laser ablation in liquid (PLAL), in which a solid target material is immersed in an organic solvent and laser beam is irradiated through liquid on a target material, is a direct method used to generate nanoparticles in liquid medium. The present work is focused on the preparation of bismuth selenide (Bi2Se3) nanoparticles using PLAL to study their field emission characteristics. The PLAL was performed under nanosecond (ns) laser with different ablation time of 120 min and 240 min. The field emission characteristics were measured in the planer “diode” configuration in all metal ultra-high vacuum (UHV) chamber. The prepared Bi2Se3 nanoparticles were analyzed with different characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy in order to study the surface morphology and structural information. The generation of Bi2Se3 nanoparticles is found after PLAL, which clearly suggests that bulk Bi2Se3 microsheet is transformed into Bi2Se3 nanoparticles. The X-ray spectra and UV spectra show the formation of nanoparticles upon laser ablation. The improvement in the field emission properties is found for laser-ablated Bi2Se3 nanoparticles. The field emission characteristics lead to increase in current density, which can be ascribed to the reduction in size of Bi2Se3 nanoparticles due to laser ablation. The prepared Bi2Se3 nanoparticles could be considered for novel applications in optoelectronics devices.

scholarly journals Design and operation of extremely high vacuum field emission electron gun.

Shinku ◽  
1986 ◽  
Vol 29 (11) ◽  
pp. 544-548 ◽  
Author(s):  
Yoshio ISHIZAWA ◽  
Susumu AOKI ◽  
Chuhei OSHIMA ◽  
Shigeki OTANI
Keyword(s):  
Field Emission ◽  
High Vacuum ◽  
Electron Gun ◽  
Vacuum Field ◽  
Emission Electron

Emission Characteristics of the Mo-Coated Silicon Tips

1996 ◽  
Vol 424 ◽  
Author(s):  
Heung-Woo Park ◽  
Byeong-Kwon Ju ◽  
Jae-Hoon Jung ◽  
Yun-Hi Lee ◽  
Jung-Ho Park ◽  
...  
Keyword(s):  
Field Emission ◽  
High Vacuum ◽  
Reactive Ion Etching ◽  
Current Fluctuations ◽  
Emission Characteristics ◽  
Ion Etching ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
High Vacuum Environment

AbstractUniform and reproducible silicon tip arrays were fabricated using the reactive ion etching followed by the re-oxidation sharpening. Molybdenum was then coated on the some of the silicon tip array. Current-voltage characteristics and current fluctuations were measured in the high vacuum environment. Field emission currents were proved by the Fowler-Nordheim plot studies.

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

A Field Emission System For Transmission Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 298-299
Author(s):  
Michel Troyonal ◽  
Huei Pei Kuoal ◽  
Benjamin M. Siegelal
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Optical System ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Electron Optical System ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Emission System

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).

Optical characteristics of the hitachi HF-2000 cold field-emission TEM

1993 ◽  
Vol 51 ◽  
pp. 1076-1077
Author(s):  
L. F. Allard ◽  
E. Völkl ◽  
T. A. Nolan
Keyword(s):  
Field Emission ◽  
Recent Literature ◽  
Electron Gun ◽  
High Brightness ◽  
Condenser Lens ◽  
Illumination System ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Better Than ◽  
Illuminating System

The illumination system of the cold field emission (CFE) Hitachi HF-2000 TEM operates with a single condenser lens in normal imaging mode, and with a second condenser lens excited to give the ultra-fine 1 nm probe for microanalysis. The electron gun provides a guaranteed high brightness of better than 7×l08 A/cm2/sr, more than twice the guaranteed brightness of Schottky emission guns. There have been several articles in the recent literature (e.g. refs.) which claim that the geometry of this illumination system yields a total current which is so low that when the beam is spread at low magnifications (say 10 kX), the operator must “keep his eyes glued to the binoculars” in order to see the image. It is also claimed that this illuminating system produces an isoplanatic patch (the area over which image character does not vary significantly) at high magnification which is so small that the instrument is ineffective for recording high resolution images.

Sign in / Sign up

Export Citation Format

Share Document