Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

FROM A COMPACT TO A RUGGED BORDER IN RAMIFIED COPPER ELECTRODEPOSITS

Fractals ◽  
1996 ◽  
Vol 04 (01) ◽  
pp. 7-16 ◽  
Author(s):  
D. OTERO ◽  
G. MARSHALL ◽  
S. TAGTACHIAN
Keyword(s):  
Electron Microscopy ◽  
Chemical Composition ◽  
Thin Layer ◽  
Relative Concentration ◽  
Building Blocks ◽  
Bragg Diffraction ◽  
X Rays ◽  
Main Interest ◽  
Well Differentiated ◽  
Shape And Size

We study the origin of the rugged border of thin-layer ramified copper electrodeposits influenced by chemical perturbations. Our main interest is to look for the smallest growth building blocks toward the understanding of the transition from a compact to a rugged structure. Using electron microscopy, we found two building blocks, well differentiated in shape and size, consisting of: (a) Spikes or rods of a diameter between 100 and 500 nm and a maximum observed length of up to 10 μm; and (b) crystalline grains with a diameter between 200 nm and 2 μm. Through X-rays Bragg diffraction, we tentatively assessed a Cu2O and metallic Cu chemical composition to the crystals and rods, respectively. The relative concentration of metallic Cu to Cu2O changes as we move from the base to the front of the aggregation and this result could be associated with the Hecker effect.

Formation of CdxHg1-xTe Layers on CdTe after NP-Etching and HgTe-Graphite Pasting

2003 ◽  
Vol 763 ◽  
Author(s):  
Yanfa Yan ◽  
K.M. Jones ◽  
X. Wu ◽  
M.M. Al-Jassim
Keyword(s):  
Electron Microscopy ◽  
Chemical Composition ◽  
High Resolution ◽  
Thin Layer ◽  
Thermal Annealing ◽  
High Resolution Electron Microscopy ◽  
Epitaxial Relationship ◽  
Single Crystalline ◽  
Resolution Electron ◽  
Cdte Films

AbstractWe report on our investigation of the microstructure and chemical composition at the CdTe/Te-rich interfaces generated by NP-etching polycrystalline and single-crystalline CdTe films and followed with HgTe-graphite pasting and thermal annealing. We find that after this process, a thin layer of CdxHg1-xTe forms between CdTe and Te-rich layers, giving a structure like CdTe/CdxHg1-xTe/Te. High-resolution electron microscopy reveals that the CdxHg1-xTe layer has an epitaxial relationship with the CdTe. No CdxHg1-xTe layer has been observed in bromine/methanol-etched samples or samples with intentionally deposited Te layers.

One Million Direct Magnification Microscopy

1971 ◽  
Vol 29 ◽  
pp. 166-167
Author(s):  
J. A. Hugo ◽  
V. A. Phillips
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Illumination Level ◽  
Level Of Detail ◽  
Photographic Emulsion ◽  
Low Contrast ◽  
Fluorescent Screen ◽  
Resolution Electron ◽  
Lattice Images ◽  
Electron Microscopes

A continuing problem in high resolution electron microscopy is that the level of detail visible to the microscopist while he is taking a picture is inferior to that obtainable by the microscope, readily readable on a photographic emulsion and visible in an enlargement made from the plate. Line resolutions, of 2Å or better are now achievable with top of the line 100kv microscopes. Taking the resolution of the human eye as 0.2mm, this indicates a need for a direct viewing magnification of at least one million. However, 0.2mm refers to optimum viewing conditions in daylight or the equivalent, and certainly does not apply to a (colored) image of low contrast and illumination level viewed on a fluorescent screen through a glass window by the dark-adapted eye. Experience indicates that an additional factor of 5 to 10 magnification is needed in order to view lattice images with line spacings of 2 to 4Å. Fortunately this is provided by the normal viewing telescope supplied with most electron microscopes.

Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

1992 ◽  
Vol 50 (1) ◽  
pp. 106-107
Author(s):  
H.W. Zandbergen ◽  
M.R. McCartney
Keyword(s):  
Electron Microscopy ◽  
Copper Oxide ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Oxygen Deficiency ◽  
Surface Layers ◽  
Layer Sequence ◽  
Surface Reconstructions ◽  
Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

Image quality vs data obtainment in biological electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 42-43
Author(s):  
J. E. Johnson
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Electron Beam ◽  
Image Quality ◽  
High Speed ◽  
Early Period ◽  
Early Years ◽  
Fluorescent Screen ◽  
Embedding Medium

In the early years of biological electron microscopy, scientists had their hands full attempting to describe the cellular microcosm that was suddenly before them on the fluorescent screen. Mitochondria, Golgi, endoplasmic reticulum, and other myriad organelles were being examined, micrographed, and documented in the literature. A major problem of that early period was the development of methods to cut sections thin enough to study under the electron beam. A microtome designed in 1943 moved the specimen toward a rotary “Cyclone” knife revolving at 12,500 RPM, or 1000 times as fast as an ordinary microtome. It was claimed that no embedding medium was necessary or that soft embedding media could be used. Collecting the sections thus cut sounded a little precarious: “The 0.1 micron sections cut with the high speed knife fly out at a tangent and are dispersed in the air. They may be collected... on... screens held near the knife“.

Quantitative energy-filtered electron diffraction

1994 ◽  
Vol 52 ◽  
pp. 992-993
Author(s):  
R. Vincent
Keyword(s):  
Electron Diffraction ◽  
Inelastic Scattering ◽  
Dynamic Range ◽  
Electron Optics ◽  
Surface Layers ◽  
High Brightness ◽  
Inclined Surfaces ◽  
Perfect Symmetry ◽  
Amorphous Surface ◽  
The Ideal

Microanalysis and diffraction on a sub-nanometre scale have become practical in modern TEMs due to the high brightness of field emission sources combined with the short mean free paths associated with both elastic and inelastic scattering of incident electrons by the specimen. However, development of electron diffraction as a quantitative discipline has been limited by the absence of any generalised theory for dynamical inelastic scattering. These problems have been simplified by recent innovations, principally the introduction of spectrometers such as the Gatan imaging filter (GIF) and the Zeiss omega filter, which remove the inelastic electrons, combined with annual improvements in the speed of computer workstations and the availability of solid-state detectors with high resolution, sensitivity and dynamic range.Comparison of experimental data with dynamical calculations imposes stringent requirements on the specimen and the electron optics, even when the inelastic component has been removed. For example, no experimental CBED pattern ever has perfect symmetry, departures from the ideal being attributable to residual strain, thickness averaging, inclined surfaces, incomplete cells and amorphous surface layers.

Novel Approaches to Low-Voltage Scanning Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 366-367
Author(s):  
Arthur V. Jones
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Electron Optics ◽  
Current Interest ◽  
New Concepts ◽  
Opportune Time ◽  
Novel Approaches ◽  
Voltage Scanning ◽  
Scanning Electron

In comparison with the developers of other forms of instrumentation, scanning electron microscope manufacturers are among the most conservative of people. New concepts usually must wait many years before being exploited commercially. The field emission gun, developed by Albert Crewe and his coworkers in 1968 is only now becoming widely available in commercial instruments, while the innovative lens designs of Mulvey are still waiting to be commercially exploited. The associated electronics is still in general based on operating procedures which have changed little since the original microscopes of Oatley and his co-workers.The current interest in low-voltage scanning electron microscopy will, if sub-nanometer resolution is to be obtained in a useable instrument, lead to fundamental changes in the design of the electron optics. Perhaps this is an opportune time to consider other fundamental changes in scanning electron microscopy instrumentation.

scholarly journals Kerogen nanoscale structure and CO2 adsorption in shale micropores

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aleksandra Gonciaruk ◽  
Matthew R. Hall ◽  
Michael W. Fay ◽  
Christopher D. J. Parmenter ◽  
Christopher H. Vane ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Chemical Composition ◽  
Focused Ion Beam ◽  
Gas Adsorption ◽  
Ion Beam ◽  
Molecular Size ◽  
Gas Sorption ◽  
Nanoscale Structures ◽  
Adsorption Sites ◽  
Nanoscale Structure

AbstractGas storage and recovery processes in shales critically depend on nano-scale porosity and chemical composition, but information about the nanoscale pore geometry and connectivity of kerogen, insoluble organic shale matter, is largely unavailable. Using adsorption microcalorimetry, we show that once strong adsorption sites within nanoscale network are taken, gas adsorption even at very low pressure is governed by pore width rather than chemical composition. A combination of focused ion beam with scanning electron microscopy and transmission electron microscopy reveal the nanoscale structure of kerogen includes not only the ubiquitous amorphous phase but also highly graphitized sheets, fiber- and onion-like structures creating nanoscale voids accessible for gas sorption. Nanoscale structures bridge the current gap between molecular size and macropore scale in existing models for kerogen, thus allowing accurate prediction of gas sorption, storage and diffusion properties in shales.

scholarly journals Surface Texture of Microcrystalline Tunnel-Structured Manganese(IV) Oxides: Nitrogen Sorptiometry and Electron Microscopy Studies

2002 ◽  
Vol 20 (7) ◽  
pp. 619-632 ◽  
Author(s):  
A.A. Ali ◽  
F.A. Al-Sagheer ◽  
M.I. Zaki
Keyword(s):  
Electron Microscopy ◽  
Chemical Composition ◽  
Surface Texture ◽  
Particle Morphology ◽  
High Resolution Electron Microscopy ◽  
Surface Chemical ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Surface Chemical Composition ◽  
Resolution Electron

Three different modifications of manganese(IV) oxide, viz. cryptomelane, nsutite and todorokite-like, were synthesized by hydrothermal methods. The bulk chemical composition, phase composition, crystalline structure and particle morphology of the resulting materials were determined by thermogravimetry, atomic absorption spectroscopy, X-ray diffractometry, infrared spectroscopy and scanning electron microscopy. The surface chemical composition, texture and structure were assessed using X-ray photoelectron microscopy, nitrogen sorptiometry and high-resolution electron microscopy. The results highlighted the hydrothermal conditions under which such tunnel-structured modifications of manganese(IV) oxide can be successfully synthesized. Moreover, they revealed that (i) the bulk was microcrystalline, (ii) the crystallites were either fibrils (cryptomelane and nsutite) or rod-like (todorokite) with low-index exposed facets, (iii) the surface chemical composition mostly reflected that of the bulk and (iv) the surface texture was linked with high specific areas, slit-shaped mesopores associated with particle interstices and micropores which allowed surface accessibility to the bulk tunnels of the test oxides. The application of such test oxides as shape-selective oxidation catalysts appears worthy of investigation.

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