scholarly journals Material Contrast Information at the limit: Imaging of energy related materials with Backscattered Electrons obtained with Field Emission and the DELTA SEM

2021 ◽  
Vol 27 (S1) ◽  
pp. 3134-3136
Author(s):  
Ute Golla-Schindler ◽  
Irene Wacker ◽  
Bernd Schindler ◽  
Ralf Löffler ◽  
Dagmar Goll ◽  
...  
Keyword(s):  
Field Emission ◽  
Backscattered Electrons ◽  
Material Contrast ◽  
Contrast Information

Development of a Field Emission VP-SEM and Some Initial Applications

2001 ◽  
Vol 7 (S2) ◽  
pp. 882-883
Author(s):  
Masako Nishimura ◽  
Sukehiro Itoh ◽  
Steve Joens
Keyword(s):  
Field Emission ◽  
Chamber Pressure ◽  
Variable Pressure ◽  
Natural State ◽  
Backscattered Electrons ◽  
Pumping System ◽  
Multi Stage ◽  
Gas Molecules ◽  
Residual Gas ◽  
Differential Pumping

The use of variable pressure SEMs (VP-SEMs) is increasing in various fields of science and industry, allowing microscopy in a variable pressure environment of 1 ∼ 270 Pa utilizing backscattered electrons for imaging. The VP-SEM allows microscopy of insulated samples without the need for sample preparation. Charging artifacts can be minimized as well. When the VP-SEM is operated with a cooling stage, which allows cooling of samples at −20° and above, vaporization of water from samples is reduced. This permits microscopy of wet samples at close to the natural state for extended periods of time.Poor S/N ratio and deterioration of resolution, both of which are due to collisions among residual gas molecules and primary/backscattered electrons, have limited the performance of VP-SEMs. For resolving these limitations, we have completed the development of a new field emission VP-SEM which operates with a stable Schottky field emission source, a new environmental secondary electron detector (ESED), and a multi-stage differential pumping system. Fig. 1 shows a sectional view of the column with the differential pumping system. This design allows stable gun vacuum conditions with variable specimen chamber pressure 10 through 3,000 Pa, permitting a pressure difference from the gun by 1011 Pa without problems.

scholarly journals Imaging low-dimensional nanostructures by very low voltage scanning electron microscopy: ultra-shallow topography and depth-tunable material contrast

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Laura Zarraoa ◽  
María U. González ◽  
Álvaro San Paulo
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Core Shell ◽  
Contrast Imaging ◽  
Backscattered Electrons ◽  
Low Voltage Operation ◽  
Material Contrast ◽  
Low Dimensional ◽  
Scanning Electron

Abstract We demonstrate the implications of very low voltage operation (<1 kV) of a scanning electron microscope for imaging low-dimensional nanostructures where standard voltages (2–5 kV) involve a beam penetration depth comparable to the cross-section of the nanostructures. In this common situation, image sharpness, contrast quality and resolution are severely limited by emission of secondary electrons far from the primary beam incidence point. Oppositely, very low voltage operation allows reducing the beam-specimen interaction to an extremely narrow and shallow region around the incidence point, enabling high-resolution and ultra-shallow topographic contrast imaging by high-angle backscattered electrons detection on the one hand, and depth-tunable material contrast imaging by low-angle backscattered electrons detection on the other. We describe the performance of these imaging approaches on silicon nanowires obtained by the vapor-liquid-solid mechanism. Our experimental results, supported by Monte Carlo simulations of backscattered electrons emission from the nanowires, reveal the self-assembly of gold-silica core-shell nanostructures at the nanowire tips without any ad-hoc thermal oxidation step. This result demonstrates the capacity of very low voltage operation to provide optimum sharpness, contrast and resolution in low-dimensional nanostructures and to gather information about nanoscaled core-shell conformations otherwise impossible to obtain by standard scanning electron microscopy alone.

Image Formation With Upper and Lower Secondary Electron Detectors in the Low Voltage Field-Emission SEM

1998 ◽  
Vol 4 (S2) ◽  
pp. 260-261
Author(s):  
J. Liu
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Incident Beam ◽  
Sample Surface ◽  
Backscattered Electrons ◽  
Sample Chamber ◽  
Scale Surface ◽  
Short Working

High-resolution secondary electron (SE) imaging was first demonstrated at 100 kV in the STEM a decade ago. High-resolution SE imaging is now routinely obtainable in field-emission SEMs. Although nanometer-scale surface features can be examined at low incident beam voltages we still do not fully understand the factors that affect the contrast of low voltage SE images. At high incident beam voltages, SE1 (SEs generated by the incident probe) and SE2 (SEs generated by backscattered electrons at the sample surface) can be spatially separated. SE1 carries high-resolution detail while SE2 contributes to background. At low incident beam voltages, however, the interaction volume of the incident electrons shrinks rapidly with decreasing incident beam voltage. Thus, both the SE1 and SE2 signals carry high-resolution information. At low incident beam voltages, SE3 (SEs generated by backscattered electrons impinging on the sample chamber, pole pieces and etc.) also carries high-resolution detail and contributes significantly to the collected signal, especially for high atomic number materials and at short working distances.

Approaches to Quantitative Electron Detection in the Scanning Electron Microscope for Topographic Studies

1990 ◽  
Vol 48 (1) ◽  
pp. 370-371
Author(s):  
Jan Hejna
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Relief ◽  
Primary Beam ◽  
Dimensional Metrology ◽  
Backscattered Electrons ◽  
Dimensional Measurements ◽  
Backscattered Electron ◽  
Material Contrast ◽  
Scanning Electron

An electron signal in the scanning electron microscope (SEM) usually consists of contributions caused by different contrast mechanisms. The most common in practice are material and topographic contrasts. Quantification of material contrast is rather a simple matter. A backscattered electron detector placed over a specimen gives mainly material contrast which can be quantified by the use of a multichannel analyser like in the energy-dispersive x-ray spectrometry.In case of topographic contrast two problems arise. One of them is dimensional metrology, especially linewidth measurements in microelectronics, the second is reconstruction of a surface relief. The first problem needs detection conditions at which the results of SEM measurements correspond exactly with real dimensions, the second needs a signal which is related with a known formula to a local surface inclination and a procedure for converting the signal into the surface relief.Experiments in the SEM and Monte-Carlo calculations have shown that results of dimensional measurements depend on an energy of a primary beam, on a type of detected electrons (secondary electrons (SE) or backscattered electrons (BSE)) and on a type of a detector.The use of low primary beam voltages and BSE is advisable, The problem of a poor efficiency of BSE detectors at low primary beam voltages can be overcome by accelerating BSE, after they have passed through a grid rejecting SE, by high voltage applied to a scintillator in a BSE detector.

scholarly journals Imaging Li–Ion Battery Material with Low Voltage Backscattered Electrons – comparison of a Field Emission SEM Crossbeam540/Merlin with the DELTA SEM

2019 ◽  
Vol 25 (S2) ◽  
pp. 448-449
Author(s):  
U. Golla-Schindler ◽  
I. Wacker ◽  
B. Schindler ◽  
T. Bernthaler ◽  
G. Schneider ◽  
...  
Keyword(s):  
Field Emission ◽  
Low Voltage ◽  
Li Ion Battery ◽  
Backscattered Electrons ◽  
Li Ion ◽  
Battery Material

Chemical Quantitative Analysis of Small Precipitates in the FE-SEM Using the Energy Distribution of Backscattered Electrons

1998 ◽  
Vol 4 (S2) ◽  
pp. 254-255
Author(s):  
Raynald Gauvin
Keyword(s):  
Field Emission ◽  
Low Voltage ◽  
Collection Efficiency ◽  
Emission Source ◽  
Incident Electron Energy ◽  
X Ray ◽  
Backscattered Electrons ◽  
Small Probe ◽  
Probe Size ◽  
Characterization Of Materials

Low voltage scanning electron microscopy with a field emission source allows characterization of materials with high spatial resolution. This high resolution comes from the low incident energy which gives a small interaction volume (about 10 nm in Fe at 1 keV ), from the field emission source which gives a small probe size (about 2.5 nm in the most recent FE-SEM) and from virtual, or through the lens, secondary electron detectors with gives high collection efficiency and eliminates some of the SEII and all the SEIII- For example, it has been shown that 10 nm NbC inclusions in steels can be imaged in such FE-SEM at 2 keV (this work was performed with a HITACHI S-4500). However, quantitative x-ray analysis of such precipitates are difficult because the critical ionization energy of the Nb Lα lines is equal to 2.37 keV, an incident electron energy of at least 5 keV must be used to get significant x-ray counts rates.

On the Microanalysis of Small Precipitates at Low Voltage with a FE-SEM

1999 ◽  
Vol 5 (S2) ◽  
pp. 308-309
Author(s):  
Raynald Gauvin ◽  
Pierre Hovington
Keyword(s):  
Field Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Chromatic Aberration ◽  
Incident Electron Energy ◽  
Objective Lens ◽  
Type I ◽  
Backscattered Electrons ◽  
Electron Microscopes ◽  
Scanning Electron

The observation of microstructural features smaller than 300 nm is generally performed using Transmission Electron Microscopy (TEM) because conventional Scanning Electron Microscopes (SEM) do not have the resolution to image such small phases. Since the early 1990’s, a new generation of microscopes is now available on the market. These are the Field Emission Gun Scanning Electron Microscope with a virtual secondary electron detector. The field emission gun gives a higher brightness than those obtained using conventional electron filaments allowing enough electrons to be collected to operate the microscope with incident electron energy, E0, below 5 keV, with probe diameter smaller than 2.5 nm. Furthermore, what gives FE-SEM outstanding resolution is the combination of new magnetic lenses with a virtual secondary electron (SE) detector. The new lenses are designed to reduce the spherical and chromatic aberration coefficients, giving a smaller probe size. Contrary to the conventional systems, the SE detector is located above the objective lens and it becomes a virtual or through-the-lens (TTL) detector. Therefore, the SE image is mostly made up of all SEs of type I, almost eliminating those of type II and III which are generated by the backscattered electrons inside the specimen as well as in the chamber. It has been shown recently that Nb(CN) precipitates in Fe, as small than 10 nm, can be imaged with a FE-SEM Hitachi S-4500 with the TTL detector.

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