Contrast in Scanning Images of Thin Crystals

1972 ◽  
Vol 30 ◽  
pp. 520-521
Author(s):  
S. Kimoto ◽  
H. Hashimoto ◽  
S. Takashima ◽  
R. M. Stern ◽  
T. Ichinokawa
Keyword(s):  
Crystal Surface ◽  
Solid Angle ◽  
Incident Angle ◽  
Intensity Variation ◽  
Lattice Defects ◽  
Scanning Microscope ◽  
Electron Detector ◽  
Backscattered Electrons ◽  
Electron Image ◽  
Backscattered Electron

The most well known application of the scanning microscope to the crystals is known as Coates pattern. The contrast of this image depends on the variation of the incident angle of the beam to the crystal surface. The defect in the crystal surface causes to make contrast in normal scanning image with constant incident angle. The intensity variation of the backscattered electrons in the scanning microscopy was calculated for the defect in the crystals by Clarke and Howie. Clarke also observed the defect using a scanning microscope.This paper reports the observation of lattice defects appears in thin crystals through backscattered, secondary and transmitted electron image. As a backscattered electron detector, a p-n junction detector of 0.9 π solid angle has been prepared for JSM-50A. The gain of the detector itself is 1.2 x 104 at 50 kV and the gain of additional AC amplifier using band width 100 Hz ∼ 10 kHz is 106.

Low-loss electron image in the sem

1983 ◽  
Vol 41 ◽  
pp. 2-5
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Solid Angle ◽  
Primary Energy ◽  
Wide Angle ◽  
Low Loss ◽  
Backscattered Electrons ◽  
Electron Image ◽  
Takeoff Angle ◽  
Scintillator Detector ◽  
Scanning Electron

The idea of filtering the backscattered electrons (BSE) in the scanning electron microscope (SEM) in order to improve the spatial resolution was suggested by McMullan (1953a) as follows: “...the beam from the specimen could be restricted to the electrons which have lost only small amounts of energy and which have therefore travelled only short distances through the specimen.” BSE which have lost less than about 1% of the primary energy can be called “low-loss electrons” or LLE (Wells 1971). As compared with LLE, the reflected electron peak contains electrons that have lost essentially no energy (Seiler 1983).Data on BSE and LLE from solid targets was given by Kanter (1957) and by Wolf, Coane and Everhart (1970). The wide-angle scintillator detector for BSE (in which the scintillator subtends a large solid angle at the specimen) was investigated by Smith (1956) and by Everhart (1958). The importance of the takeoff angle with this detector was shown experimentally by Wells (1957 and 1970).

Optimizing the collector solid angle for the low-loss electron image in the Scanning Electron Microscope

1987 ◽  
Vol 45 ◽  
pp. 548-549 ◽  
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Solid Angle ◽  
Angle Of Incidence ◽  
Tungsten Filament ◽  
Low Loss ◽  
Backscattered Electrons ◽  
Glancing Angle ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is formed by collecting backscattered electrons (BSE) that have lost less than a specified energy. Compared to the secondary electron (SE) image, these images are less affected by specimen charging and show the surface topography clearly when examining uncoated photoresist. However, LLE images sometimes contain dark shadows caused by the limited solid angle of the LLE detector. Here, we describe a way to position the sample (with a given LLE detector) so as to reduce these shadows as far as possible.The SEM was a Cambridge S-250 Mk. III with a tungsten filament. An experimental LLE detector was added. The SE image was obtained using the SE detector ordinarily present in the SEM.The LLE detector is shown in Fig. 1. The specimen is mounted close to the lens in the SEM with a glancing angle of incidence of 30°.

Contrast and Resolution in Scanning Electron Microscopes

1967 ◽  
Vol 25 ◽  
pp. 256-257
Author(s):  
Shizuo Kimoto ◽  
Hiroshi Hashimoto ◽  
Kiyoshi Mase
Keyword(s):  
Secondary Electron ◽  
Primary Electron ◽  
Secondary Electron Image ◽  
Scattered Electron ◽  
Secondary Electrons ◽  
Backscattered Electrons ◽  
Electron Image ◽  
Backscattered Electron ◽  
Electron Microscopes ◽  
Scanning Electron

In scanning electron microscopy, secondary and backscattered electrons play a most important role. When considering these two forms of signal source, it is necessary to treat them separately on the basis of contrast and resolution, since their production processes and energies are different. In practice, the electrons detected by the secondary electron detector consist of secondary electrons excited by a primary electron probe, those excited by backscattered electrons in the specimen and secondary electrons liberated from the specimen's environmental parts during backscattered electron bombardment. Consequently, it is difficult to completely eradicate the effect of backscattered electrons upon the secondary electron image. This paper presents information in regards to the differences in contrast and resolution between the secondary and back- scattered electron image under the condition of optimum secondary/backscattered electron separation. First, it was shown how secondary electron image contrast is affected by secondary electrons liberated by backscattered electrons.

Use of backscattered electron image intensity signals to calculate the water/cement ratio of concrete

1992 ◽  
Vol 50 (1) ◽  
pp. 356-357
Author(s):  
R. J. Lee ◽  
A. J. Schwoeble ◽  
Yuan Jie
Keyword(s):  
Reliable Data ◽  
X Ray ◽  
Rapid Measurement ◽  
Trained Personnel ◽  
Electron Image ◽  
Backscattered Electron ◽  
Production Period ◽  
Strength And Durability ◽  
Automated Procedures ◽  
Standard Density

Water/Cement (W/C) ratio is a very important parameter affecting the strength and durability of concrete. At the present time, there are no ASTM methods for determining W/C ratio of concrete structures after the production period. Existing techniques involving thin section standard density comparative associations using light optical microscopy and rely on visual comparisons using standards and require highly trained personnel to produce reliable data. This has led to the exploration of other methods utilizing automated procedures which can offer a precise and rapid measurement of W/C ratio. This paper discusses methods of determining W/C ratio using a scanning electron microscope (SEM) backscattered electron image (BEI) intensity signal and x-ray computer tomography.

The use of high-resolution FESEM to study solid-state phase transformations and reactions

1994 ◽  
Vol 52 ◽  
pp. 1028-1029
Author(s):  
P. G. Kotula ◽  
D. D. Erickson ◽  
C. B. Carter
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Phase Transformations ◽  
High Efficiency ◽  
Sol Gel ◽  
Quantitative Information ◽  
Solid State Reactions ◽  
Critical Dimensions ◽  
Backscattered Electrons ◽  
Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

High-sensitivity detection of gold labels by high-angle dark-field STEM imaging

1990 ◽  
Vol 48 (3) ◽  
pp. 892-893 ◽  
Author(s):  
Max T. Otten
Keyword(s):  
High Sensitivity ◽  
Dark Field ◽  
Bright Field ◽  
Backscattered Electron Imaging ◽  
Backscattered Electrons ◽  
Average Atomic Number ◽  
Highly Sensitive ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
High Sensitivity Detection

Labelling of antibodies with small gold probes is a highly sensitive technique for detecting specific molecules in biological tissue. Larger gold probes are usually well visible in TEM or STEM Bright-Field images of unstained specimens. In stained specimens, however, the contrast of the stain is frequently the same as that of the gold labels, making it virtually impossible to identify the labels, especially when smaller gold labels are used to increase the sensitivity of the immunolabelling technique. TEM or STEM Dark-Field images fare no better (Figs. 1a and 2a), again because of the absence of a clear contrast difference between gold labels and stain.Potentially much more useful is backscattered-electron imaging, since this will show differences in average atomic number which are sufficiently large between the metallic gold and the stains normally used. However, for the thin specimens and at high accelerating voltages of the STEM, the yield of backscattered electrons is very small, resulting in a very weak signal. Consequently, the backscattered-electron signal is often too noisy for detecting small labels, even for large spot sizes.

New Multifunctional Detector Unit for SEM

2000 ◽  
Vol 6 (S2) ◽  
pp. 736-737
Author(s):  
T. Dolukhanyan ◽  
V. Galstyan ◽  
C. Nielsen ◽  
C. Sung
Keyword(s):  
Solid Angle ◽  
Spherical Surface ◽  
Schematic Diagram ◽  
Pole Piece ◽  
Secondary Electrons ◽  
Backscattered Electrons ◽  
Highly Efficient ◽  
Bottom Side

In order to increase analytical capabilities of SEM we have developed a multifunctional detector unit, which allows the simultaneous and highly efficient registration of the information from the chosen area of the specimen using backscattered electrons (BSE) and cathodoluminescent (CL) radiation. At the same time secondary electrons (SE) could be collected by the regular Everhart - Thornley detector. Thus, the unit allows to perform microstructural investigations in three modes of SEM operation simultaneously - BSE, CL and SE. A schematic diagram of the unit is presented in Fig. 1.In the plate made of scintillating material, and installed between the pole piece of SEM and the specimen, the bottom side is a part of spherical surface. The surface covers completely the whole top surface of the specimen and collects BSE and CL radiation in the solid angle ∼2 π sr.

Sign in / Sign up

Export Citation Format

Share Document