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.

Current State of Biological High-Resolution Scanning Electron Microscopy

1988 ◽  
Vol 46 ◽  
pp. 180-181 ◽  
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Performance ◽  
Low Voltage ◽  
Backscattered Electrons ◽  
Lens Position ◽  
Low Voltage Operation ◽  
Signal Collection ◽  
Probe Size ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

A new generation of high performance field emission scanning electron microscopes (FSEM) is now commercially available (JEOL 890, Hitachi S 900, ISI OS 130-F) characterized by an "in lens" position of the specimen where probe diameters are reduced and signal collection improved. Additionally, low voltage operation is extended to 1 kV. Compared to the first generation of FSEM (JE0L JSM 30, Hitachi S 800), which utilized a specimen position below the final lens, specimen size had to be reduced but useful magnification could be impressively increased in both low (1-4 kV) and high (5-40 kV) voltage operation, i.e. from 50,000 to 200,000 and 250,000 to 1,000,000 x respectively.At high accelerating voltage and magnification, contrasts on biological specimens are well characterized1 and are produced by the entering probe electrons in the outmost surface layer within -vl nm depth. Backscattered electrons produce only a background signal. Under these conditions (FIG. 1) image quality is similar to conventional TEM (FIG. 2) and only limited at magnifications >1,000,000 x by probe size (0.5 nm) or non-localization effects (%0.5 nm).

High spatial resolution x-ray microanalysis of interfaces

1995 ◽  
Vol 53 ◽  
pp. 284-285
Author(s):  
J. R. Michael
Keyword(s):  
Spatial Resolution ◽  
Electron Probe ◽  
Solid Angle ◽  
Collection Efficiency ◽  
Spatial Scales ◽  
Energy Dispersive Spectrometer ◽  
X Rays ◽  
X Ray ◽  
Probe Size ◽  
Brightness Field

X-ray microanalysis in the analytical electron microscope (AEM) refers to a technique by which chemical composition can be determined on spatial scales of less than 10 nm. There are many factors that influence the quality of x-ray microanalysis. The minimum probe size with sufficient current for microanalysis that can be generated determines the ultimate spatial resolution of each individual microanalysis. However, it is also necessary to collect efficiently the x-rays generated. Modern high brightness field emission gun equipped AEMs can now generate probes that are less than 1 nm in diameter with high probe currents. Improving the x-ray collection solid angle of the solid state energy dispersive spectrometer (EDS) results in more efficient collection of x-ray generated by the interaction of the electron probe with the specimen, thus reducing the minimum detectability limit. The combination of decreased interaction volume due to smaller electron probe size and the increased collection efficiency due to larger solid angle of x-ray collection should enhance our ability to study interfacial segregation.

Micro Auger analysis using a field emission source

1978 ◽  
Vol 36 (1) ◽  
pp. 516-517
Author(s):  
P.E. Bovey ◽  
I.R.M. Wardell ◽  
P.M. Williams
Keyword(s):  
Field Emission ◽  
High Current Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Emission Source ◽  
Auger Analysis ◽  
Sem Image ◽  
Probe Diameter ◽  
Small Probe ◽  
Experimental Vessel

The use of a high brightness field emission source holds clear promise in the area of micro Auger analysis of surfaces. The high current density and small probe diameter obtainable from the field emitter (30 n A into 300Ǻ, for example) offer the possibility of recording Auger spectra from areas less than 300Ǻ, as previously demonstrated . Furthermore, the ultra high vacuum technology necessary for a reliable field emission source, is wholly compatible with the type of vacuum experimental vessel customary in surface analysis applications.We describe here results obtained with an HB50A Auger Microprobe in which an environmental cell, introduced on a bellows movement into the experimental vessel, permits heating to 800°C in an atmosphere of 0.1 torr of gas. The sample under study was pure polycrystalline iron.This was reacted with methane at 750°C in situ for 12 hours. The carbon resulting from cracked methane, dissolved in the iron to such an extent that, on cooling to 600˚C, precipitation occured. Figure 1 shows an SEM image of a characteristic precipitate, recorded with the sample held at 600˚C at a magnification of 2,000 X.

Multi-layer thin-film deposition for high-performance X-ray field-emission characteristics

2021 ◽  
pp. 2140043
Author(s):  
Tae Hwan Jang ◽  
Tae Gyu Kim ◽  
Mun Ki Bae ◽  
Kyuseok Kim ◽  
Jaegu Choi
Keyword(s):  
Thin Film ◽  
Field Emission ◽  
High Performance ◽  
Low Voltage ◽  
High Vacuum ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
X Ray ◽  
Emission Effect ◽  
Layer Thin Film

In this study, we developed a nanoscale emitter having a multi-layer thin-film nanostructure in an effort to maximize the field-emission effect with a low voltage difference. The emitter was a sapphire board on which tungsten–DLC multi-player thin film was deposited using PVD and CVD processes. This multi-layer thin-film emitter was examined in a high-vacuum X-ray tube system. Its field-emission efficiency according to the applied voltage was then analyzed.

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.

Low Voltage X-Ray Microanalysis of Bulk Bio-Organic Samples

1998 ◽  
Vol 4 (S2) ◽  
pp. 190-191
Author(s):  
Patrick Echlin
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Spatial Resolution ◽  
High Voltage ◽  
Biological Material ◽  
High Spatial Resolution ◽  
Low Voltage ◽  
Similar Type ◽  
The Other ◽  
X Ray

Although high resolution (2nm), low voltage (lkV), SEM of bio-organic materials can now be performed more or less routinely using instruments fitted with a field emission source, virtually no low voltage x-ray microanalysis has been carried out on this type of specimen. Boyes and Nockolds showed that quantitative microanalytical information could be obtained from polished inorganic samples at a spatial resolution of l00nm at 5kV and Johnson et al obtained similar type of data at a spatial resolution of 150nm at 3kV. High spatial resolution (l0nm) microanalysis can be achieved in frozen dried or chemically compromised sections of biological material examined at high voltage in the TEM but frozen hydrated chemically unfixed sections are damaged. The other approach is to use the SEM with frozen hydrated, chemically uncompromised samples, usually at about 10-15kV, in order to obtain sufficient signal from the elements of interest which typically lie in the range Na (Z=l 1) to Ca (Z=20).

Sign in / Sign up

Export Citation Format

Share Document