Progress on the subangstrom field emission scanning transmission electron microscope

1991 ◽  
Author(s):  
Shengyang Ruan ◽  
Oscar H. Kapp
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

A Prototype Field-Emission Scanning Transmission Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 296-297
Author(s):  
J.R. Banbury ◽  
U. R. Bance
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Wide Range ◽  
Scanning Transmission ◽  
Further Development ◽  
Diode Voltage

A prototype field emission scanning transmission electron microscope has been constructed and is under further development at AEI Scientific Apparatus Limited.The field emission gun has a triode construction, with geometry such as to produce a divergent beam from a virtual source whose position remains substantially constant over a wide range of total accelerating voltages. The gun has been operated satisfactorily from below 10 kV to over 90 kV (upper limit set by power supplies), with the field emission diode voltage typically between 2 kV and 4 kV and total emission of a few microamps. Single-crystal tungsten tips of either (111) or (310) orientation are used, though (310) tips normally produce a superior probe current stability.

An Analytical Scanning Transmission Electron Microscope

1975 ◽  
Vol 33 ◽  
pp. 130-131
Author(s):  
H. von Harrach ◽  
C.E. Lyman ◽  
A.R. Walker ◽  
D.C. Joy ◽  
G.R. Booker
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Loss Analysis ◽  
Scanning Transmission Electron ◽  
Quantitative Microanalysis ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

A scanning transmission electron microscope (STEM) with a field emission gun has been developed for quantitative microanalysis. The high brightness source combined with X-ray analysis, electron diffraction and electron energy loss analysis provides a technique of microanalysis from regions of thin specimens as small as a few hundred angstroms.The electron optical lay-out of this microscope is shown in Figure 1. A triode field-emission gun is mounted in a U HV chamber with mu-metal walls for screening. The gun which can be operated at up to 100kV provides a virtual source; the position of this source is largely independent of the ratio of the acceleration voltage to extraction voltage.

RDF Analysis of Ion-Amorphized SiO2 and SiC from Electron Diffraction using Post-Specimen Scanning in the Field-Emission Scanning Transmission Electron Microscope

1997 ◽  
Vol 504 ◽  
Author(s):  
David C. Bell ◽  
Anthony J. Garratt-Reed ◽  
Linn W. Hobbst
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Field Emission ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

ABSTRACTRadial density functions (RDFs) provide important information about short- and ntermediaterange structure of topologically-disordered materials such as glasses and irradiation-amorphized materials. We have determined RDFs for irradiation-amorphized SiO2, AIPO4 and SiC by energy-filtered electron diffraction methods in a field-emission scanning transmission electron microscope (FEG-STEM) equipped with a digital parallel-detection electron energy-loss spectrometer. Post-specimen rocking was used to minimize the effects of spherical aberration in the objective lens, which interfere with the acquisition of data collected by pre-specimen rocking. Useful energy-filtered data has been collected beyond an angular range defined by q = 2 sin(Θ/2)/λ = 25 nm−1

A General Method for Spectrometer Design in the Scoff Approximation

1976 ◽  
Vol 34 ◽  
pp. 538-539
Author(s):  
J. R. Fields
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Energy Analysis ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Chemical Identification ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
General Method

The energy analysis of electrons scattered by a specimen in a scanning transmission electron microscope can improve contrast as well as aid in chemical identification. In so far as energy analysis is useful, one would like to be able to design a spectrometer which is tailored to his particular needs. In our own case, we require a spectrometer which will accept a parallel incident beam and which will focus the electrons in both the median and perpendicular planes. In addition, since we intend to follow the spectrometer by a detector array rather than a single energy selecting slit, we need as great a dispersion as possible. Therefore, we would like to follow our spectrometer by a magnifying lens. Consequently, the line along which electrons of varying energy are dispersed must be normal to the direction of the central ray at the spectrometer exit.

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

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