High energy resolution spectrometer for the dedicated STEM

1984 ◽  
Vol 42 ◽  
pp. 558-559 ◽  
Author(s):  
P.E. Batson
Keyword(s):  
Collection Efficiency ◽  
Core Loss ◽  
Beam Current ◽  
High Energy ◽  
High Energy Resolution ◽  
Acquisition Time ◽  
Good Definition ◽  
Loss Analysis ◽  
Definition Of ◽  
Acceleration Voltage

Use of the STEM to obtain precise electronic information has been hampered by the lack of energy loss analysis capable of a resolution and accuracy comparable to the 0.3eV energy width of the Field Emission Source. Recent work by Park, et. al. and earlier by Crewe, et. al. have promised magnetic sector devices that are capable of about 0.75eV resolution at collection angles (about 15mR) which are great enough to allow efficient use of the STEM probe current. These devices are also capable of 0.3eV resolution at smaller collection angles (4-5mR). The problem that arises, however, lies in the fact that, even with the collection efficiency approaching 1.0, several minutes of collection time are necessary for a good definition of a typical core loss or electronic transition. This is a result of the relatively small total beam current (1-10nA) that is available in the dedicated STEM. During this acquisition time, the STEM acceleration voltage may fluctuate by as much as 0.5-1.0V.

Silicon Carbide for Alpha, Beta, Ion and Soft X-Ray High Performance Detectors

2005 ◽  
Vol 483-485 ◽  
pp. 1015-1020 ◽  
Author(s):  
Giuseppe Bertuccio ◽  
Simona Binetti ◽  
S. Caccia ◽  
R. Casiraghi ◽  
Antonio Castaldini ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Collection Efficiency ◽  
High Energy ◽  
Beta Particle ◽  
High Energy Resolution ◽  
Charge Collection Efficiency ◽  
X Ray ◽  
Current Densities ◽  
Full Charge

High performance SiC detectors for ionising radiation have been designed, manufactured and tested. Schottky junctions on low-doped epitaxial 4H-SiC with leakage current densities of few pA/cm2 at room temperature has been realised at this purpose. The epitaxial layer has been characterised at different dose of radiations in order to investigate the SiC radiation hardness. The response of the detectors to alpha and beta particle and to soft X-ray have been measured. High energy resolution and full charge collection efficiency have been successfully demonstrated.

Atomic-Level EELS Mapping Using High-Energy Edges in Dualeels™ Mode

2012 ◽  
Vol 20 (4) ◽  
pp. 30-36 ◽  
Author(s):  
Paolo Longo ◽  
Paul J. Thomas ◽  
Ray D. Twesten
Keyword(s):  
Collection Efficiency ◽  
High Energy ◽  
Atomic Level ◽  
Acquisition Time ◽  
Elemental Distribution ◽  
Aberration Correction ◽  
Resolution Limit ◽  
Probe Size ◽  
Scanning Transmission ◽  
Atomic Coordination

With advancements in aberration correction, the spatial resolution of scanning transmission electron microscopy (STEM) has been enormously improved. In addition to the reduction of the STEM probe size, a dramatic increase in the STEM probe current has been realized, leading to the routine acquisition of high-resolution elemental and chemical maps using electron energy loss spectrometry (EELS). Using EELS combined with these advanced STEM instruments, atomic-level resolution information can be obtained from various types of materials, revealing the nature of interfaces, elemental distribution, presence of defects, and much more. In addition to simple elemental composition distributions, EELS is capable of delivering information about the chemical bonding, local atomic coordination, oxidation states, band gaps, and chemical phases of a broad range of materials at the fundamental resolution limit of the property being probed. Atomic-level EELS maps of these fundamental material properties can now be obtained with the acquisition time, to a large extent, limited only by the speed of the EELS spectrometer and not by the signal being measured. The availability of fast EELS spectrometers with large angular collection efficiencies has closed the gap between the rate of signal generation in the specimen and the speed at which this signal can be detected. This significantly increases the amount of information that can be acquired using EELS. Using the most recent generation of spectrometers, EELS data can be acquired at well over 1,000 spectra per second with a high-duty cycle. Fifth-order spectral aberration correction in this generation of spectrometers allows the use of the large collection angles needed to match the increased convergence angle that Cs-probe-corrected systems present, improving collection efficiency while maintaining energy resolution. These advances, when taken together, result in a well matched source/detector system capable of recording high-energy EELS edges at atomic resolution at a rate fast enough to limit electron beam damage to the sample.

A new analytical electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 18-19
Author(s):  
N.W. Parker ◽  
A.V. Crewe ◽  
M.S. Isaacson ◽  
W. Mankawich
Keyword(s):  
High Energy ◽  
High Energy Resolution ◽  
Small Particles ◽  
Loss Analysis ◽  
Large Current ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Current Electron ◽  
Current Densities ◽  
Electron Energy Loss

In recent years there has been increasing interest in the ability to perform electron energy loss analysis of areas approaching 20Å in size. We have initiated a program to study the electronic structure of small particles (≳ 10Å diameter) of grain boundaries and to perform EXAFS-type analysis of a variety of materials. For all of these studies, it is necessary to have reasonably high energy resolution (≲ .5 eV) and to focus large current electron beams down to spot diameters of 20Å or less (1). For EXAFS this is important since one is interested in few percent modulations of signals due to inner shell excitations (which by themselves are many orders of magnitude weaker than the signals due to plasmon or valence shell excitations). In the analysis of small particles, the signals are weak due to the small number of atoms within the probe, so high current densities are needed to avoid extremely long counting times.

scholarly journals LÉVY FLIGHT OF HOLES IN InP SEMICONDUCTOR SCINTILLATOR

2012 ◽  
Vol 21 (01) ◽  
pp. 1250001 ◽  
Author(s):  
SERGE LURYI ◽  
ARSEN SUBASHIEV
Keyword(s):  
Heavy Tails ◽  
Collection Efficiency ◽  
High Energy ◽  
High Energy Resolution ◽  
Slab Thickness ◽  
Lévy Flight ◽  
Levy Flight ◽  
Charge Collection Efficiency ◽  
Radiative Efficiency ◽  
Photon Collection

High radiative efficiency in moderately doped n- InP results in the transport of holes dominated by photon-assisted hopping, when radiative hole recombination at one spot produces a photon, whose interband absorption generates another hole, possibly far away. Due to "heavy tails" in the hop probability, this is a random walk with divergent diffusivity (process known as the Lévy flight). Our key evidence is derived from the ratio of transmitted and reflected luminescence spectra, measured in samples of different thicknesses. These experiments prove the non-exponential decay of the hole concentration from the initial photo-excitation spot. The power-law decay, characteristic of Lévy flights, is steep enough at short distances (steeper than an exponent) to fit the data for thin samples and slow enough at large distances to account for thick samples. The high radiative efficiency makes possible a semiconductor scintillator with efficient photon collection. It is rather unusual that the material is "opaque" at wavelengths of its own scintillation. Nevertheless, after repeated recycling most photons find their way to one of two photodiodes integrated on both sides of the semiconductor slab. We present an analytical model of photon collection in two-sided slab, which shows that the heavy tails of Lévy-flight transport lead to a high charge collection efficiency and hence high energy resolution. Finally, we discuss a possibility to increase the slab thickness while still quantifying the deposited energy and the interaction position within the slab. The idea is to use a layered semiconductor with photon-assisted collection of holes in narrow-bandgap layers spaced by distances far exceeding diffusion length. Holes collected in these radiative layers emit longwave radiation, to which the entire structure is transparent. Nearly-ideal calculated characteristics of a mm-thick layered scintillator can be scaled up to several centimeters.

An efficient X-ray spectrometer based on thin mosaic crystal films and its application in various fields of X-ray spectroscopy

2009 ◽  
Vol 42 (4) ◽  
pp. 572-579 ◽  
Author(s):  
Herbert Legall ◽  
Holger Stiel ◽  
Matthias Schnürer ◽  
Marcel Pagels ◽  
Birgit Kanngießer ◽  
...  
Keyword(s):  
Solid Angle ◽  
Collection Efficiency ◽  
High Energy ◽  
High Energy Resolution ◽  
Spectroscopic Methods ◽  
Weak Signal ◽  
X Ray ◽  
Mosaic Crystal ◽  
Crystal Films ◽  
Mosaic Crystals

X-ray optics with high energy resolution and collection efficiency are required in X-ray spectroscopy for investigations of chemistry and coordination. This is particularly the case if the X-ray source emits a rather weak signal into a large solid angle. In the present work the performance of a spectrometer based on thin mosaic crystals was investigated for different spectroscopic methods using various X-ray sources. It was found that, even with low-power X-ray sources, advanced high-resolution X-ray spectroscopy can be performed.

Use of Polycapillary Optics to Increase the Effective Area of Microcalorimeter Spectrometers

1997 ◽  
Vol 3 (S2) ◽  
pp. 1075-1076 ◽  
Author(s):  
D. A. Wollman ◽  
Christopher Jezewski ◽  
G. C. Hilton ◽  
Qi-Fan Xiao ◽  
K. D. Irwin ◽  
...  
Keyword(s):  
Energy Resolution ◽  
Count Rate ◽  
Small Area ◽  
Solid Angle ◽  
Collection Efficiency ◽  
High Energy ◽  
High Energy Resolution ◽  
X Rays ◽  
X Ray ◽  
Broad Energy Range

Although the performance of high-energy-resolution microcalorimeter spectrometers for x-ray microanalysis is encouraging, the future widespread acceptance of these spectrometers as valuable microanalysis instruments depends on improvements in both achievable count rate and geometrical x-ray collection efficiency. While the maximum output count rate of our microcalorimeter (∼160 s−1) is much less than that of conventional EDS detectors operating at their highest energy resolution (∼3000 s−1), we are confident that we can significantly improve the count rate without loss of energy resolution (∼10 eV FWHM over a broad energy range). Increasing the area (and thus solid angle) of the microcalorimeter is a more difficult problem, however, as the best microcalorimeter performance is achieved using small-area (typically 250 μm by 250 μm) absorbers with low heat capacity.This problem can be solved by using an x-ray lens to increase the collection efficiency of the microcalorimeter spectrometer. A polycapillary optic consisting of tens of thousands of fused capillaries can collect x-rays from a point x-ray source over a large solid angle and focus the x-rays onto the small-area absorber of the microcalorimeter.

Comparison of Techniques for EELS Mapping in Biology

1996 ◽  
Vol 54 ◽  
pp. 300-301
Author(s):  
R.D. Leapman ◽  
S.B. Andrews
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Image Data ◽  
Beam Current ◽  
Quantitative Information ◽  
Acquisition Time ◽  
Uniform Thickness ◽  
Electron Dose ◽  
Array Detectors ◽  
Transmission Electron

Elemental mapping of biological specimens by electron energy loss spectroscopy (EELS) can be carried out both in the scanning transmission electron microscope (STEM), and in the energy-filtering transmission electron microscope (EFTEM). Choosing between these two approaches is complicated by the variety of specimens that are encountered (e.g., cells or macromolecules; cryosections, plastic sections or thin films) and by the range of elemental concentrations that occur (from a few percent down to a few parts per million). Our aim here is to consider the strengths of each technique for determining elemental distributions in these different types of specimen.On one hand, it is desirable to collect a parallel EELS spectrum at each point in the specimen using the ‘spectrum-imaging’ technique in the STEM. This minimizes the electron dose and retains as much quantitative information as possible about the inelastic scattering processes in the specimen. On the other hand, collection times in the STEM are often limited by the detector read-out and by available probe current. For example, a 256 x 256 pixel image in the STEM takes at least 30 minutes to acquire with read-out time of 25 ms. The EFTEM is able to collect parallel image data using slow-scan CCD array detectors from as many as 1024 x 1024 pixels with integration times of a few seconds. Furthermore, the EFTEM has an available beam current in the µA range compared with just a few nA in the STEM. Indeed, for some applications this can result in a factor of ~100 shorter acquisition time for the EFTEM relative to the STEM. However, the EFTEM provides much less spectral information, so that the technique of choice ultimately depends on requirements for processing the spectrum at each pixel (viz., isolated edges vs. overlapping edges, uniform thickness vs. non-uniform thickness, molar vs. millimolar concentrations).

Analysis of Voltage Contrast in Secondary Electron Images Using a High-Energy Electron Spectrometer

2019 ◽  
Author(s):  
Natsuko Asano ◽  
Shunsuke Asahina ◽  
Natasha Erdman
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Sample Surface ◽  
High Energy ◽  
Secondary Electrons ◽  
Analysis Technique ◽  
Quantitative Understanding ◽  
Voltage Contrast ◽  
Acceleration Voltage ◽  
Failure Localization

Abstract Voltage contrast (VC) observation using a scanning electron microscope (SEM) or a focused ion beam (FIB) is a common failure analysis technique for semiconductor devices.[1] The VC information allows understanding of failure localization issues. In general, VC images are acquired using secondary electrons (SEs) from a sample surface at an acceleration voltage of 0.8–2.0 kV in SEM. In this study, we aimed to find an optimized electron energy range for VC acquisition using Auger electron spectroscopy (AES) for quantitative understanding.

scholarly journals Energy loss separation in NiFeMo compacts with smoothed powders according to Landgraf’s and Bertotti’s theories

2021 ◽  
Author(s):  
Denisa Olekšáková ◽  
Peter Kollár ◽  
Miloš Jakubčin ◽  
Ján Füzer ◽  
Martin Tkáč ◽  
...  
Keyword(s):  
Energy Loss ◽  
Mechanical Treatment ◽  
Positive Impact ◽  
Core Loss ◽  
Low Frequency ◽  
Treatment Method ◽  
Effective Dimension ◽  
Loss Analysis ◽  
Innovative Method ◽  
Individual Particles

AbstractThis submitted paper presents the detailed description of the energy loss separation for dc and ac low-frequency magnetic fields of NiFeMo (supermalloy) compacted powder prepared by innovative method of smoothing the surfaces of individual particles. The positive impact of mechanical treatment method on domain wall displacement is explained on the basis of Landgraf approach for dc loss analysis, and the effective dimension for eddy current in ac magnetic field is explained according to Bertotti approach for core loss analysis.

scholarly journals Lying, speech acts, and commitment

Synthese ◽  
2020 ◽  
Author(s):  
Neri Marsili
Keyword(s):  
Speech Acts ◽  
Speech Act ◽  
Good Definition ◽  
Definition Of ◽  
The Right ◽  
Adequate Analysis

AbstractNot every speech act can be a lie. A good definition of lying should be able to draw the right distinctions between speech acts (like promises, assertions, and oaths) that can be lies and speech acts (like commands, suggestions, or assumptions) that under no circumstances are lies. This paper shows that no extant account of lying is able to draw the required distinctions. It argues that a definition of lying based on the notion of ‘assertoric commitment’ can succeed where other accounts have failed. Assertoric commitment is analysed in terms of two normative components: ‘accountability’ and ‘discursive responsibility’. The resulting definition of lying draws all the desired distinctions, providing an intensionally adequate analysis of the concept of lying.

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