APPLICATIONS OF STEM INSTRUMENTS FOR SURFACE STUDIES

Scanning transmission electron microscopy (STEM) instruments have some particular advantages as compared with the more common transmission electron microscopes for some applications to surface research. Imaging of surfaces and mapping of the elemental distributions on surfaces with spatial resolutions approaching 1 nm are possible in an ultrahigh-vacuum STEM instrument when the low-energy secondary electrons or the Auger-emitted electrons are collected with high efficiency. In the imaging of surface layers on thin-film substrates, viewed in transmission, the use of a thin annular detector in STEM may greatly enhance the contrast, as illustrated by the case of the imaging of very thin nanocrystalline carbon layers on much thicker amorphous SiO2 films. The scanning reflection mode in a STEM instrument can provide some useful forms of contrast in images of surface structure. Standing wave fields can be formed on the surfaces of crystals with electrons, as with X-rays, one advantage of the electron case being that the standing wave fields may be imaged. Two new forms of electron holography, involving a STEM instrument and suitable for the study of surface structure, are proposed.

Download Full-text

Reflection Electron Microscopy and Diffraction from Crystal Surfaces

MRS Proceedings ◽

10.1557/proc-31-177 ◽

1983 ◽

Vol 31 ◽

Cited By ~ 3

Author(s):

J.M. Cowley

Keyword(s):

Electron Microscopy ◽

Surface Structure ◽

Crystal Surfaces ◽

Local Composition ◽

Surface Steps ◽

Transmission Electron ◽

Scanning Transmission ◽

Reflection Electron Microscopy ◽

Electron Microscopes ◽

Geometric Effects

ABSTRACTThe recent revival of techniques for the imaging of crystal surfaces, using electrons forward-scattered in the RHEED mode and employing modern electron microscopes, has lead to the introduction of valuable new methods for the study of surface structure. Either fixed beam or scanning transmission electron microscopy (STEM) instruments may be used and in each case a lateral resolution of 10Å or better is possible. Simple theoretical treatments suggest that the contrast from surface steps may be attributed to a combination of phase-contrast, diffraction contrast and geometric effects. With a STEM instrument the image information can be combined with information on the local composition and crystal structure by use of microanalysis and microdiffraction techniques. Examples of applications include studies of the surface structure of metals, semiconductors and oxides, and the surface reactions.

Download Full-text

New capabilities for `colouring in' the chemistry of crystal defects atom-by-atom

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314023055 ◽

2014 ◽

Vol 70 (6) ◽

pp. 521-523

Author(s):

Sarah J. Haigh

Keyword(s):

High Resolution ◽

High Efficiency ◽

Crystal Defects ◽

Energy Dispersive ◽

Acta Cryst ◽

X Ray ◽

Elemental Imaging ◽

Transmission Electron ◽

Scanning Transmission ◽

Electron Microscopes

The latest generation of scanning transmission electron microscopes equipped with high-efficiency energy-dispersive X-ray detectors are breaking new ground with respect to high-resolution elemental imaging of materials. In this issue, Paulauskaset al.[Acta Cryst.(2014), A70, 524–531] demonstrate impressive results when applying this technique to improve understanding of CdTe dislocation structures.

Download Full-text

Development of a 1MV-Field-Emission Electron Microscope I. Instrument

Microscopy and Microanalysis ◽

10.1017/s1431927600038186 ◽

2000 ◽

Vol 6 (S2) ◽

pp. 1138-1139

Author(s):

I. Matsui ◽

T. Katsuta ◽

T. Kawasaki ◽

S. Hayashi ◽

T. Furutsu ◽

...

Keyword(s):

Electron Microscope ◽

Field Emission ◽

Transmission Electron Microscope ◽

Scanning Transmission Electron Microscope ◽

Electron Holography ◽

Lorentz Microscopy ◽

Transmission Electron ◽

Scanning Transmission ◽

Resolution Imaging ◽

Electron Microscopes

We have developed 100-kV, 200-kV, and 350-kV cold-field-emission transmission electron microscopes (FE-TEMs) successively up to this time. Using these instruments, we have been studying the magnetic structure of materials, high-resolution imaging by electron holography, and dynamic observation of the vortex in superconductors by Lorentz microscopy. To make more progress in our research, we need a better electron beam in terms of coherency, beam brightness, and penetration. Here, we report a new lMV-cold-field-emission transmission electron microscope we have developed. Historically, the pioneering projects on a lMV-field-emission scanning transmission electron microscope (FE-STEM) (Zeitler and Crewe, 1974) and a 1.6MV FE-STEM (Jouffrey et al., 1984) have been reported. In 1988, Maruse and Shimoyama obtained a lMV-field-emission beam using their 1.25MV-STEM connected to a field-emission gun. Since then, continuous improvements in beam brightness has been made.The target specifications of our 1 MV-cold-field-emission TEM (H-1000FT) are as follows: Acceleration voltage: 1MV, high-voltage stability :

Download Full-text

STEM microanalysis of precipitates in a nickel-base superalloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109707 ◽

1978 ◽

Vol 36 (1) ◽

pp. 512-513

Author(s):

A.J. Craven ◽

R.G. Menzies ◽

R.H. Bricknell

Keyword(s):

Analytical Techniques ◽

Nickel Base Superalloy ◽

X Rays ◽

Metal Carbides ◽

Transmission Electron ◽

Scanning Transmission ◽

Electron Microscopes ◽

Nickel Base ◽

Electron Energy Loss ◽

Base Superalloy

In a powder compacted nickel-base superalloy used in high temperature applications, a group of metal carbides (MC) 200-600nm in diameter were observed. Many of these precipitates contained an inner particle (20-60nm in diameter) which will be referred to as the nucleus. In addition to the commercial interest in such a metallurgical system, the identification of the two types of particles provides an interesting problem in microanalysis. Currently two analytical techniques are available on the VG Microscopes HB5, scanning transmission electron microscopes (STEM); energy dispersive X-ray analysis (EDX) and transmission electron energy loss spectroscopy (TEELS).When analysing thinned foils there is the problem of interference from a layer of matrix on the precipitate or from the outer precipitate surrounding the nucleus. Even if the foil is thinned to the extent that layering effects are removed EDX still suffers two drawbacks; (i) Inadequate collimation leads to system peaks following general specimen illumination; (ii) X-rays and electrons leaving the area analysed generate characteristic peaks from adjacent regions.

Download Full-text

The Theoretical Contrast in Scanning and Conventional High Resolution Microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062762 ◽

1969 ◽

Vol 27 ◽

pp. 170-171

Author(s):

E. Zeitler ◽

M. G. R. Thomson

Keyword(s):

Small Volume ◽

Volume Element ◽

Optical Processing ◽

Image Construction ◽

Object Interaction ◽

Transmission Electron ◽

Scanning Transmission ◽

Optical Treatment ◽

Electron Microscopes ◽

Intensity Contrast

In the formation of an image each small volume element of the object is correlated to an areal element in the image. The structure or detail of the object is represented by changes in intensity from element to element, and this variation of intensity (contrast) is determined by the interaction of the electrons with the specimen, and by the optical processing of the information-carrying electrons. Both conventional and scanning transmission electron microscopes form images which may be considered in this way, but the mechanism of image construction is very different in the two cases. Although the electron-object interaction is the same, the optical treatment differs.

Download Full-text

Reduction of Specimen Contamination in Electron-Beam Instruments

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092840 ◽

1976 ◽

Vol 34 ◽

pp. 576-577

Author(s):

G. Lehmpfuhl ◽

P. J. Smith

Keyword(s):

Electron Beam ◽

Cold Trap ◽

Beam Diameter ◽

Transmission Electron ◽

Scanning Transmission ◽

Hydrocarbon Molecules ◽

Electron Microscopes ◽

Combination Of Methods ◽

Convergent Beam ◽

Very High

Specimens being observed with electron-beam instruments are subject to contamination, which is due to polymerization of hydrocarbon molecules by the beam. This effect becomes more important as the size of the beam is reduced. In convergent-beam studies with a beam diameter of 100 Å, contamination was observed to grow on samples at very high rates. Within a few seconds needles began forming under the beam on both the top and the underside of the sample, at growth rates of 400-500 Å/s, severely limiting the time available for observation. Such contamination could cause serious difficulty in examining a sample with the new scanning transmission electron microscopes, in which the beam is focused to a few angstroms.We have been able to reduce the rate of contamination buildup by a combination of methods: placing an anticontamination cold trap in the sample region, preheating the sample before observation, and irradiating the sample with a large beam before observing it with a small beam.

Download Full-text

Imaging and diffraction modes in Scanning Transmission Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144814 ◽

1986 ◽

Vol 44 ◽

pp. 684-687

Author(s):

J. M. Cowley ◽

R. Glaisher ◽

J. A. Lin ◽

H.-J. Ou

Keyword(s):

Scanning Transmission Electron Microscopy ◽

High Efficiency ◽

Fiber Optic ◽

Image Intensifier ◽

Detector System ◽

Detector Plane ◽

Secondary Electrons ◽

Transmission Electron ◽

Scanning Transmission ◽

Special Detector

Some of the most important applications of STEM depend on the variety of imaging and diffraction made possible by the versatility of the detector system and the serial nature, of the image acquisition. A special detector system, previously described, has been added to our STEM instrument to allow us to take full advantage of this versatility. In this, the diffraction pattern in the detector plane may be formed on either of two phosphor screens, one with P47 (very fast) phosphor and the other with P20 (high efficiency) phosphor. The light from the phosphor is conveyed through a fiber-optic rod to an image intensifier and TV system and may be photographed, recorded on videotape, or stored digitally on a frame store. The P47 screen has a hole through it to allow electrons to enter a Gatan EELS spectrometer. Recently a modified SEM detector has been added so that high resolution (10Å) imaging with secondary electrons may be used in conjunction with other modes.

Download Full-text

In-Situ Electrochemical Transmission Electron Microscopy for Battery Research

Microscopy and Microanalysis ◽

10.1017/s1431927614000488 ◽

2014 ◽

Vol 20 (2) ◽

pp. 484-492 ◽

Cited By ~ 30

Author(s):

B. Layla Mehdi ◽

Meng Gu ◽

Lucas R. Parent ◽

Wu Xu ◽

Eduard N. Nasybulin ◽

...

Keyword(s):

Electron Beam ◽

Silicon Nanowires ◽

Electrochemical Processes ◽

Transmission Electron ◽

Experimental Parameters ◽

Scanning Transmission ◽

Electrode Interface ◽

Electron Microscopes

AbstractThe recent development of in-situ liquid stages for (scanning) transmission electron microscopes now makes it possible for us to study the details of electrochemical processes under operando conditions. As electrochemical processes are complex, care must be taken to calibrate the system before any in-situ/operando observations. In addition, as the electron beam can cause effects that look similar to electrochemical processes at the electrolyte/electrode interface, an understanding of the role of the electron beam in modifying the operando observations must also be understood. In this paper we describe the design, assembly, and operation of an in-situ electrochemical cell, paying particular attention to the method for controlling and quantifying the experimental parameters. The use of this system is then demonstrated for the lithiation/delithiation of silicon nanowires.

Download Full-text

High-Efficiency Three-Dimensional Visualization of Complex Microstructures via Multidimensional STEM Acquisition and Reconstruction

Microscopy and Microanalysis ◽

10.1017/s1431927620000173 ◽

2020 ◽

Vol 26 (2) ◽

pp. 240-246 ◽

Cited By ~ 1

Author(s):

Kevin G. Field ◽

Benjamin P. Eftink ◽

Chad M. Parish ◽

Stuart A. Maloy

Keyword(s):

High Efficiency ◽

3D Visualization ◽

Accurate Determination ◽

Three Dimensional ◽

High Energy ◽

Scanning Transmission Electron Microscope ◽

Chromium Steel ◽

Transmission Electron ◽

Scanning Transmission

AbstractComplex material systems in which microstructure and microchemistry are nonuniformly dispersed require three-dimensional (3D) rendering(s) to provide an accurate determination of the physio-chemical nature of the system. Current scanning transmission electron microscope (STEM)-based tomography techniques enable 3D visualization but can be time-consuming, so only select systems or regions are analyzed in this manner. Here, it is presented that through high-efficiency multidimensional STEM acquisition and reconstruction, complex point cloud-like microstructural features can quickly and effectively be reconstructed in 3D. The proposed set of techniques is demonstrated, analyzed, and verified for a high-chromium steel with heterogeneously situated features induced using high-energy neutron bombardment.

Download Full-text