Low-voltage SEM update

1986 ◽  
Vol 44 ◽  
pp. 654-657
Author(s):  
J.B. Pawley ◽  
W.R. Scala
Keyword(s):  
High Resolution ◽  
Low Voltage ◽  
Low Energy ◽  
Special Issue ◽  
Significant Progress ◽  
Beam Voltage ◽  
Signal Collection ◽  
Upper Stage ◽  
Micro Lens ◽  
Made In

The advantages of operating an SEM at low beam voltage (Vo) are now widely recognized and significant progress has been made in overcoming the practical limitations to high resolution operation with Vo = 1-2 kV. A Symposium on Low Voltage SEM (LVSEM) was held at the 1984 EMSA meeting and several of the papers presented there were later collected for a special issue of the Journal of Microscopy. The purpose of this contribution is to outline three developments in instrumentation for LVSEM that have recently appeared. These include: 1) The new pole-pieces on the upper stage of the ISI DS-130c which permit it to produce very low aberration coefficients with low energy beams. 2) The replacement of the final lens of the Hitachi S-800, field emission SEM with an immersion lens to create the new S-900; 3) The development of the micro-lens for mounting in the chamber on a conventional’ SEM to produce both low aberration coefficients and a favorable geometry for signal collection.

scholarly journals Editorial of Special Issue “Nanostructured Light-Emitters”

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 601
Author(s):  
Hieu P. T. Nguyen
Keyword(s):  
Nanostructured Materials ◽  
Light Emitting Diodes ◽  
Laser Diodes ◽  
Optoelectronic Devices ◽  
Special Issue ◽  
Significant Progress ◽  
Light Emitters ◽  
Light Emitting ◽  
Nanophotonic Devices ◽  
Made In

Significant progress has been made in the development of nanophotonic devices and the use of nanostructured materials for optoelectronic devices, including light-emitting diodes (LEDs) and laser diodes, has recently attracted tremendous attention due to the fact of their unique geometry [...]

scholarly journals An Overview of Computational MHD Jets and Their Comparisons with Recent High Resolution Radio Images

1990 ◽  
Vol 140 ◽  
pp. 403-412
Author(s):  
David A. Clarke
Keyword(s):  
High Resolution ◽  
Numerical Simulations ◽  
Stokes Parameters ◽  
Synchrotron Emission ◽  
Significant Progress ◽  
Astrophysical Jets ◽  
Axisymmetric Jet ◽  
Radio Jets ◽  
Made In

Significant progress has been made in comparing numerical simulations with radio images of astrophysical jets. One is no longer forced to compare density slices through an axisymmetric jet simulation with observed Stokes I images. With the advent of MHD codes and modern supercomputers, models can now be constrained by all four Stokes parameters. In this paper, recent efforts to simulate synchrotron emission images of extragalactic radio jets are reviewed.

scholarly journals Dark cloud observations: Problems and progress

1997 ◽  
Vol 178 ◽  
pp. 173-182
Author(s):  
Y. C. Minh
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
Recent Progress ◽  
High Resolution Spectroscopy ◽  
Significant Progress ◽  
Dark Cloud ◽  
Dark Clouds ◽  
Number Of Species ◽  
Observing Techniques ◽  
Made In

Interstellar dark clouds have provided a laboratory which has been successfully used to identify a number of species, perform high resolution spectroscopy, and characterize the processes in the interstellar medium. We have successfully solved a number of problems and achieved significant progress through dark cloud observations. With the improvement of observing techniques and theories, however, we are now having new problems and are waiting for further progress. The dark clouds, because of their quietness and large column densities, still provide a very useful testing ground of many uncertain interstellar processes. Here we summarize some of the recent progress made in dark cloud observations and discuss related problems. We focus especially on the importance of nearby objects, possible signs of gas-grain interactions in dark clouds, and further sensitive observations.

The limitations of quantitative EDS analysis at low voltage

1996 ◽  
Vol 54 ◽  
pp. 476-477
Author(s):  
C. E. Nockolds
Keyword(s):  
Quantitative Analysis ◽  
Low Voltage ◽  
Low Energy ◽  
X Rays ◽  
Considerable Effort ◽  
Beam Voltage ◽  
Absorption Correction ◽  
Transition Series ◽  
Very High ◽  
High Absorption

There are several reasons for carrying out x-ray microanalysis at low beam energies. In conventional electron probe microanalysis with wavelength dispersive spectrometers (WDS) there has been a considerable effort in recent years to improve the accuracy of quantitative analysis of the “light” elements B, C, N and O. The shapes of the low energy K x-rays and the L x-rays of the first transition series metals are also being studied with the aim of determining the chemical environments of the atoms in a sample. In most materials these soft x-rays suffer from very high absorption, and reducing the depth of the interaction volume by lowering the beam voltage to 5kV or below leads to a much reduced absorption correction. In scanning electron microscopy the introduction of thin window energy dispersive spectrometers (EDS) has made it possible to look at low energy x-rays and here the main interest in working at low voltages is in the improvement of the resolution of analysis.In this paper the limitations of SEM/EDS low voltage analysis will be examined, and possible solutions to some of the problems explored. It will be assumed that the aims are to achieve quantitative analysis at the best possible spatial resolution.

Low-voltage high-resolution SEM investigations of novel macromolecular liquid crystals

1992 ◽  
Vol 50 (1) ◽  
pp. 266-267
Author(s):  
W.W. Adams ◽  
D.L. Vezie ◽  
E.L. Thomas
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Chromatic Aberration ◽  
Low Energy ◽  
Energy Spread ◽  
Surface Topology ◽  
Conducting Layer ◽  
Successful Operation ◽  
Low Voltage Operation

The ability to visualize detailed 3-dimensional surface topology with SEM at low voltage and high resolution holds profound promise for analyzing liquid crystal textures, both in polymers and other macromolecular forms. Director textures, domain boundaries, and defects such as inversion walls, disclinations and dislocations can now be easily visualized with this technique. Studies concerning the effects of shear flow and magnetic fields on these defects are currently under way.Resolution of 4.0 nm at 1.0 keV is now possible with commercial SEM's, which incorporate the latest advances in lens design optimized for low voltage operation, and use high brightness, low energy spread field emission electron guns. The low energy spread of the field emission gun reduces chromatic aberration effects and facilitates successful operation at low keV. Low voltage operation provides dramatically improved image contrast due to the smaller beam/sample interaction volume and also greatly reduces sample charging artifacts. By operating at near crossover conditions, the need for coating nonconducting specimens with a conducting layer of metal or carbon is greatly reduced or eliminated.

scholarly journals Toward Quantitative Defect Analysis Using HREM

1996 ◽  
Vol 4 (6) ◽  
pp. 8-11
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Defect Analysis ◽  
Significant Progress ◽  
Detailed Characterization ◽  
Resolution Electron ◽  
High Resolution Images ◽  
High Resolution Electron Microscope ◽  
20 Nm ◽  
Made In

The electron microscope has evolved to the level where it is now straightforward to record high-resolution images from thin samples (t~ to 20 nm) that are directly interpretable in terms of atomic arrangements. Whilst recorded images necessarily represent two-dimensional projections of the structure, many defects such as dislocations and interfaces may be linear or planar in nature and this might be expected to be amenable to detailed characterization. In this review, we briefly consider the recent significant progress that has been made in quantitative defect analysis using the high-resolution electron microscope and then discuss some drawbacks to the technique as well as potential scope for further improvements.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

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).

SEM at Low Beam Voltage

1984 ◽  
Vol 42 ◽  
pp. 440-443
Author(s):  
James Pawley
Keyword(s):  
Low Voltage ◽  
Probe Diameter ◽  
Small Probe ◽  
Beam Voltage ◽  
Practical Constraints

Operation of the SEM with V0 = l-3kV (LVSEM) was early recognized to reduce charging artefacts and increase topographic contrast. This early promise was not pursued because several theoretical and practical considerations made it difficult to produce a small probe diameter (d0) at low voltage. Recently, the necessity of using low V0 to image uncoated semiconductors without damaging them has prompted a re-evaluation of LVSEM. This re-evaluation has taken the form of efforts to eliminate the practical constraints and to alleviate the theoretical ones. In the process, some heretofore neglected theoretical advantages of LVSEM have emerged. These problems and possibilities will now be discussed in more detail.

Toward quantitative defect analysis using HREM

1994 ◽  
Vol 52 ◽  
pp. 714-715
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscope ◽  
Unit Cell ◽  
Defect Analysis ◽  
Significant Progress ◽  
Detailed Characterization ◽  
Small Unit ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Large Unit Cell ◽  
Made In

The electron microscope has evolved to the level where it is now straightforward to record highresolution images from thin samples (t∼10 to 20nm) that are directly interpretable in terms of atomic arrangements. Whilst recorded images necessarily represent two-dimensional projections of the structure, many defects such as dislocations and interfaces may be linear or planar in nature and thus might be expected to be amenable to detailed characterization. In this review, we briefly consider the recent significant progress that has been made in quantitative defect analysis using the high-resolution electron microscope and then discuss some drawbacks to the technique as well as potential scope for further improvements. Surveys of defect modelling for some small-unit-cell materials and interfaces have recently been published, and reference should be made to other papers in this symposium for further examples.The technique of structure imaging originated in the early '70s with observations of large-unit-cell block oxides.

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