Secondary electron imaging of MoO3 reduction in a UHV STEM

1989 ◽  
Vol 47 ◽  
pp. 86-87
Author(s):  
P. A. Crozier ◽  
J. Liu ◽  
J. M. Cowley
Keyword(s):  
Electron Beam ◽  
Metal Oxides ◽  
Field Emission ◽  
Secondary Electron ◽  
Electron Beams ◽  
Exit Surface ◽  
Electron Imaging ◽  
Drill Holes ◽  
First Time ◽  
Better Than

Recently, a number of people have studied the ability of focussed electron beams to form lines and holes in metal oxides. Many metal oxides decompose when irradiated under the high intensity focussed probes used in field emission STEMS. Initially, many of these oxides reduce to the metal and in some cases it is possible to drill holes in the material. Understanding the nature of the interaction between the electron beam and the sample is important for materials characterisation. These studies may also lead to the development of new electron beam resists and masks. Here we present some preliminary results on the effect of electron irradiation on MoO3 in a field emission UHV STEM. We show, for the first time, secondary electron (SE)images of the entrance and exit surface of the sample after radiation damage has occurred.The experiments described here were performed on the VG HB501S; a dedicated STEM in which vacuums better than 10-10 torr are routinely available in the column.

SEM and microdiffraction study of the reduction of metal oxides in a STEM instrument

1988 ◽  
Vol 46 ◽  
pp. 516-517
Author(s):  
J. Liu ◽  
J. M. Cowley
Keyword(s):  
Electron Beam ◽  
Metal Oxides ◽  
Structural Information ◽  
Image Resolution ◽  
Secondary Electrons ◽  
Additional Information ◽  
Reduction Processes ◽  
Exit Surface ◽  
Reduction Of Metal Oxides ◽  
Better Than

It has been reported that under electron beam irradiation maximally valent metal oxides can be reduced to lower oxides and under some circumstances even to metals due to the preferential loss of oxygen. The electron beam induced reactions can be conveniently studied in a STEM instrument equipped with a field emission gun and a chamber vacuum pressure about 5x10-9 Torr.. Microdiffraction patterns obtained from areas about 1.0-1.5 nm in diameter can be used to deduce the structural information of the reduction products. The recently attached SE detector in our HB5 STEM instrument can collect secondary electrons at the exit surface of the sample and the image resolution is better than 1 nm3. Since SE signals carry information about the surface and sub-surface of the studied material and SE emission is sensitive to surface modifications (both geometric and electronic) such as the change of work function due to the formation of new phases on the specimen surface, high resolution SE imaging can provide additional information about the reduction processes of metal oxides under electron beam bombardment. The combination of SE imaging with the microdiffraction technique proves to be a powerful tool for studying surface reactions.

Observation of exit surface sputtering in TiO2 using biased secondary electron imaging

1990 ◽  
Vol 237 (1-3) ◽  
pp. 232-240 ◽  
Author(s):  
P.A. Crozier ◽  
M.R. McCartney ◽  
David J. Smith
Keyword(s):  
Secondary Electron ◽  
Exit Surface ◽  
Electron Imaging ◽  
Surface Sputtering

scholarly journals Thirty per cent contrast in secondary-electron imaging by scanning field-emission microscopy

2016 ◽  
Vol 472 (2195) ◽  
pp. 20160475 ◽  
Author(s):  
D. A. Zanin ◽  
L. G. De Pietro ◽  
Q. Peter ◽  
A. Kostanyan ◽  
H. Cabrera ◽  
...  
Keyword(s):  
Field Emission ◽  
Secondary Electron ◽  
Secondary Electrons ◽  
Scanning Tunnelling ◽  
Field Emission Microscopy ◽  
Tunnelling Microscopy ◽  
Emission Microscopy ◽  
Electron Imaging ◽  
Primary Electrons ◽  
Strong Contrast

We perform scanning tunnelling microscopy (STM) in a regime where primary electrons are field-emitted from the tip and excite secondary electrons out of the target—the scanning field-emission microscopy regime (SFM). In the SFM mode, a secondary-electron contrast as high as 30% is observed when imaging a monoatomic step between a clean W(110)- and an Fe-covered W(110)-terrace. This is a figure of contrast comparable to STM. The apparent width of the monoatomic step attains the 1  nm mark, i.e. it is only marginally worse than the corresponding width observed in STM. The origin of the unexpected strong contrast in SFM is the material dependence of the secondary-electron yield and not the dependence of the transported current on the tip–target distance, typical of STM: accordingly, we expect that a technology combining STM and SFM will highlight complementary aspects of a surface while simultaneously making electrons, selected with nanometre spatial precision, available to a macroscopic environment for further processing.

scholarly journals Investigation of the Effect of Structural Properties of a Vertically Standing CNT Cold Cathode on Electron Beam Brightness and Resolution of Secondary Electron Images

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1918
Author(s):  
Ha Rim Lee ◽  
Da Woon Kim ◽  
Alfi Rodiansyah ◽  
Boklae Cho ◽  
Joonwon Lim ◽  
...  
Keyword(s):  
Electron Beam ◽  
Structural Properties ◽  
Field Emission ◽  
Secondary Electron ◽  
Structural Features ◽  
Cold Cathode ◽  
Sem Images ◽  
Theoretical Simulation ◽  
Field Emission Properties ◽  
Cold Cathodes

Carbon nanotube (CNT)-based cold cathodes are promising sources of field emission electrons for advanced electron devices, particularly for ultra-high-resolution imaging systems, due to their high brightness and low energy spread. While the electron field emission properties of single-tip CNT cathodes have been intensively studied in the last few decades, a systematic study of the influencing factors on the electron beam properties of CNT cold cathodes and the resolution of the secondary electron images has been overlooked in this field. Here, we have systematically investigated the effect of the structural properties of a CNT cold cathode on the electron beam properties and resolution of secondary electron microscope (SEM) images. The aspect ratio (geometric factor) and the diameter of the tip of a vertically standing CNT cold cathode significantly affect the electron beam properties, including the beam size and brightness, and consequently determine the resolution of the secondary electron images obtained by SEM systems equipped with a CNT cold cathode module. Theoretical simulation elucidated the dependence of the structural features of CNT cold cathodes and electron beam properties on the contribution of edge-emitted electrons to the total field emission current. Investigating the correlations between the structural properties of CNT cold cathodes, the properties of the emitted electron beams, and the resolution of the secondary electron images captured by SEM equipped with CNT cold cathode modules is highly important and informative as a basic model.

scholarly journals Nonlinear electron beam guiding by a reduced-density channel

1993 ◽  
Vol 11 (4) ◽  
pp. 685-695 ◽  
Author(s):  
J.-M. Dolique ◽  
M. Khodja
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Temperature Distribution ◽  
Secondary Electron ◽  
Electron Beams ◽  
Optimal Values ◽  
Ionized Air ◽  
Reduced Density ◽  
D Model ◽  
Beam Channel

Suggested by numerical simulations, recent experiments have shown that a significant guiding force is exerted by a reduced-density channel on electron beams propagating through initially un-ionized air. A theoretical analysis of this guiding force had been given that assumed uniform beam and channel and small beam-channel offset. From a 2-D model, relative to a beam slice, the guiding force is calculated in this article for arbitrary beamchannel offset and for various smooth beam and channel profiles. This calculation confirms the above-quoted experimental evidence of a guiding force significant with respect to the deflection force exerted by the earth's magnetic field. It also confirms the crucial role played by the secondary electron temperature distribution. Finally, it suggests optimal values for the ratio between channel and beam rms radii.

High-resolution x-ray elemental images

1989 ◽  
Vol 47 ◽  
pp. 204-205
Author(s):  
C. E. Lyman ◽  
J. S. Hepburn ◽  
H. G. Stenger ◽  
J. R. Michael
Keyword(s):  
Electron Beam ◽  
Field Emission ◽  
X Ray ◽  
Electron Sources ◽  
Small Probe ◽  
Long Time ◽  
X Ray Background ◽  
Low X ◽  
Image Collection ◽  
Better Than

Field-emission electron sources and digital image collection techniques produce x-ray emission images of elemental distributions (maps) with far higher quality than those obtained by conventional x-ray dot mapping. Without a field-emission source the useful upper magnification of an x-ray image is only a few times 104X with the resolution rarely exceeding 100 nm. The images described below are routinely collected at 1,000,000x with a resolution of better than 5 nm. Such images are collected at quite low x-ray intensities and over long time periods compared to electron images. This means that the effects of x-ray background at each pixel and of image drift become important issues in the collection of meaningful images.The instrument used in this work was the Vacuum Generators HB-501 STEM equipped with a Link Systems LZ-5 windowless energy dispersive x-ray detector of 146 eV energy resolution. This instrument is equipped with a gun lens to provide several times more current in the small probe than the normal HB-501. The electron beam was 1.8 nm in diameter (FWHM) and the beam contained about 0.9 nA. The digital x-ray maps shown here were obtained with 128x128 pixels and 100 ms dwell time per pixel. With this small electron beam the image magnification should be at least 400,000x to allow the beam to fill each pixel and avoid underscanning (beam smaller than the pixel).

The interaction of electron beams with solids - Some new effects

1990 ◽  
Vol 48 (4) ◽  
pp. 788-789
Author(s):  
C J Humphreys ◽  
T J Bullough ◽  
R W Devenish ◽  
D M Maher ◽  
P S Turner
Keyword(s):  
Electron Beam ◽  
Field Emission ◽  
Electron Irradiation ◽  
Electron Beams ◽  
Incident Electron Beam ◽  
Surface Steps ◽  
Wide Range ◽  
Intense Electron Beams ◽  
Intense Electron ◽  
Scale Surface

It has recently been found that electron beams, of energy typically 100 keV, can damage a very wide range of solids, many of which are normally thought to be stable to electron irradiation. For example, metals, semiconductors and ceramics can all be damaged by electrons having energy less than that required for direct displacement damage. Radiation damage effects are particularly apparent when using intense electron beams from field emission guns in STEM's, TEM's and SEM's, but damage also occurs in materials thought to be stable when using electrons from LaB6, or heated W filaments. Considerable care must therefore be taken in microanalysis, etc, particularly when using field emission guns.If the incident electron beam is focussed to nanometre-scale diameter, then nanometre-scale surface and volume structures (e.g. indentations, holes and lines) can be produced in a variety of specimens. It is also possible to cut a specimen to a desired shape with nanometre precision and to remove surface steps from surfaces, leaving them atomically smooth.

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