Off-axis electron holography in an aberration-corrected transmission electron microscope

2009 ◽  
Vol 367 (1903) ◽  
pp. 3773-3793 ◽  
Author(s):  
Hannes Lichte ◽  
Dorin Geiger ◽  
Martin Linck
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Point Spread Function ◽  
Signal To Noise Ratio ◽  
Electron Holography ◽  
Signal To Noise ◽  
Point Spread ◽  
Transmission Electron ◽  
Spread Function ◽  
Noise Ratio

Electron holography allows the reconstruction of the complete electron wave, and hence offers the possibility of correcting aberrations. In fact, this was shown by means of the uncorrected CM30 Special Tübingen transmission electron microscope (TEM), revealing, after numerical aberration correction, a resolution of approximately 0.1 nm, both in amplitude and phase. However, it turned out that the results suffer from a comparably poor signal-to-noise ratio. The reason is that the limited coherent electron current, given by gun brightness, has to illuminate a width of at least four times the point-spread function given by the aberrations. As, using the hardware corrector, the point-spread function shrinks considerably, the current density increases and the signal-to-noise ratio improves correspondingly. Furthermore, the phase shift at the atomic dimensions found in the image plane also increases because the collection efficiency of the optics increases with resolution. In total, the signals of atomically fine structures are better defined for quantitative evaluation. In fact, the results achieved by electron holography in a Tecnai F20 Cs-corr TEM confirm this.

Dose Limited Resolution

1998 ◽  
Vol 4 (S2) ◽  
pp. 802-803
Author(s):  
D. Van Dyck ◽  
A.J. den Dekker ◽  
J. Sijbers ◽  
E. Bettens
Keyword(s):  
Point Spread Function ◽  
Communication Channel ◽  
Unit Area ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Imaging Device ◽  
Point Spread ◽  
Spread Function ◽  
Minimal Contrast ◽  
Definition Of

1. IntroductionThe definition of resolution as introduced by Lord Rayleigh [1] is related to the width of the point spread function of the imaging device. In this definition, noise has not been taken into account. Another definition of resolution has been introduced by Rose [2] in the field of radar and TV. Here the resolution is defined in terms of the dose (D) (i.e. number of imaging particles per unit area) and the signal to noise ratio SNR (i.e. the minimal contrast) A third definition of resolution is based on the idea that the microscope is a communication channel between the object and the observer. The resolution can then be rephrased as the amount of information that is transmitted by the channel in the sense as defined by Shannon [3] as a number of bits per unit area. This definition however does not describe how this information can be deduced and what its precision is.

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.

Reconstruction of electron holograms recorded in a non-FEG, non-biprism TEM

1995 ◽  
Vol 53 ◽  
pp. 618-619
Author(s):  
Z.L. Wang
Keyword(s):  
Electron Microscope ◽  
Single Crystal ◽  
Experimental Technique ◽  
Transmission Electron Microscope ◽  
The Other ◽  
Electron Holography ◽  
Transmission Electron ◽  
Coherent Sources ◽  
Imaging Theory ◽  
Normal Specimen

An experimental technique for performing electron holography using a non-FEG, non-biprism transmission electron microscope (TEM) has been introduced by Ru et al. A double stacked specimens, one being a single crystal foil and the other the specimen, are loaded in the normal specimen position in TEM. The single crystal, which is placed onto the specimen, is responsible to produce two beams that are equivalent to two virtual coherent sources illuminating the specimen beneath, thus, permitting electron holography of the specimen. In this paper, the imaging theory of this technique is described. Procedures are introduced for digitally reconstructing the holograms.

Characterization of JEOL 3000f TEM Equipped for Electron Holography

2000 ◽  
Vol 6 (S2) ◽  
pp. 228-229
Author(s):  
M. A. Schofield ◽  
Y. Zhu
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Design Of Experiment ◽  
Electron Holography ◽  
Fringe Spacing ◽  
Interference Fringes ◽  
Transmission Electron ◽  
Careful Design

Quantitative off-axis electron holography in a transmission electron microscope (TEM) requires careful design of experiment specific to instrumental characteristics. For example, the spatial resolution desired for a particular holography experiment imposes requirements on the spacing of the interference fringes to be recorded. This fringe spacing depends upon the geometric configuration of the TEM/electron biprism system, which is experimentally fixed, but also upon the voltage applied to the biprism wire of the holography unit, which is experimentally adjustable. Hence, knowledge of the holographic interference fringe spacing as a function of applied voltage to the electron biprism is essential to the design of a specific holography experiment. Furthermore, additional instrumental parameters, such as the coherence and virtual size of the electron source, for example, affect the quality of recorded holograms through their effect on the contrast of the holographic fringes.

scholarly journals Measurement of the Electron Beam Point Spread Function (PSF) in a Scanning Electron Microscope (SEM)

2015 ◽  
Vol 21 (S3) ◽  
pp. 699-700 ◽  
Author(s):  
Yudhishthir P. Kandel ◽  
Matthew D. Zotta ◽  
Andrew N. Caferra ◽  
Richard Moore ◽  
Eric Lifshin
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Point Spread Function ◽  
Point Spread ◽  
Spread Function ◽  
Scanning Electron

A Study of Membrane Impact on Spatial Resolution of Liquid In Situ Transmission Electron Microscope

2020 ◽  
Vol 26 (1) ◽  
pp. 126-133
Author(s):  
Ming Li ◽  
Ruth Knibbe
Keyword(s):  
Electron Microscope ◽  
Spatial Resolution ◽  
Transmission Electron Microscope ◽  
Signal To Noise Ratio ◽  
Chromatic Aberration ◽  
Membrane Thickness ◽  
Additional Material ◽  
Transmission Electron ◽  
The Impact

AbstractMicrochip technology with electron transparent membranes is a key component for in situ liquid transmission electron microscope (TEM) characterization. The membranes can significantly influence the TEM imaging spatial resolution, not only due to introducing additional material layers but also due to the associated bulging. The membrane bulging is largely defined by the membrane materials, thickness, and short dimension. The impact of the membrane on the spatial resolution, especially the extent of its bulging, was systematically investigated through the impact on the signal-to-noise ratio, chromatic aberration, and beam broadening. The optimization of the membrane parameters is the key component when designing the in situ TEM liquid cell. The optimal membrane thickness of 50 nm was found which balances the impact of membrane bulging and membrane thickness. Beyond this, the short membrane window dimension and the chip nominal spacing should be minimized. However, these two parameters have practical limitations in regards to chip handling.

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