scholarly journals Direct comparison of differential phase contrast and off-axis electron holography for the measurement of electric potentials by the examination of reverse biased Si p-n junctions and III-V samples

2016 ◽  
pp. 703-704
Author(s):  
Benedikt Haas ◽  
David Cooper ◽  
Jean-Luc Rouvière
Keyword(s):  
Phase Contrast ◽  
Electron Holography ◽  
Differential Phase ◽  
Electric Potentials ◽  
Differential Phase Contrast

Differential phase contrast in TEM for magnetic micro structure observation

1995 ◽  
Vol 53 ◽  
pp. 606-607
Author(s):  
P. Kruit ◽  
A.H. Buist ◽  
M.R. McCartney ◽  
M.R. Scheinfein
Keyword(s):  
Phase Contrast ◽  
Fringe Pattern ◽  
Plane Waves ◽  
Magnetic Thin Films ◽  
Electron Holography ◽  
Differential Phase ◽  
Spatial Frequencies ◽  
Structure Observation ◽  
Differential Phase Contrast ◽  
The Magnetic Field

Phase contrast in TEM can only give information in a limited band of spatial frequencies. The differential phase contrast mode in STEM does not have this limitation, since one simply measures the angle over which the electron beam is deflected by the specimen. This is useful, for example, for determining the magnetic field distribution in magnetic thin films. Recently, a form of electron holography was developed, also in STEM, to obtain differential phase contrast images. In this method, the illuminating beam is split by a biprism in such a way that there are two mutually coherent electron source images close to the specimen. On a far away CCD detector, two shadow images are formed which interfere to give a fringe pattern. It is this fringe pattern that contains the differential phase information. Here, we show that differential phase contrast can also be obtained in a TEM.In the TEM, two coherent illuminating beams are created by a beam splitter in the condenser system. These beams can be treated as two plane waves, creating a fringe pattern in the plane of observation,as shown in figure 1.

The role of differential phase contrast in electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 176-177
Author(s):  
E.M. Waddell ◽  
J.N. Chapman ◽  
R.P. Ferrier
Keyword(s):  
Phase Contrast ◽  
Practical Method ◽  
Position Vector ◽  
Differential Phase ◽  
Pure Phase ◽  
Differential Phase Contrast ◽  
The Difference ◽  
Image Position ◽  
First Moment

Dekkers and de Lang (1977) have discussed a practical method of realising differential phase contrast in a STEM. The method involves taking the difference signal from two semi-circular detectors placed symmetrically about the optic axis and subtending the same angle (2α) at the specimen as that of the cone of illumination. Such a system, or an obvious generalisation of it, namely a quadrant detector, has the characteristic of responding to the gradient of the phase of the specimen transmittance. In this paper we shall compare the performance of this type of system with that of a first moment detector (Waddell et al.1977).For a first moment detector the response function R(k) is of the form R(k) = ck where c is a constant, k is a position vector in the detector plane and the vector nature of R(k)indicates that two signals are produced. This type of system would produce an image signal given bywhere the specimen transmittance is given by a (r) exp (iϕ (r), r is a position vector in object space, ro the position of the probe, ⊛ represents a convolution integral and it has been assumed that we have a coherent probe, with a complex disturbance of the form b(r-ro) exp (iζ (r-ro)). Thus the image signal for a pure phase object imaged in a STEM using a first moment detector is b2 ⊛ ▽ø. Note that this puts no restrictions on the magnitude of the variation of the phase function, but does assume an infinite detector.

scholarly journals Ultrasound differential phase contrast using backscattering and the memory effect

2021 ◽  
Vol 118 (12) ◽  
pp. 124103
Author(s):  
Timothy D. Weber ◽  
Nikunj Khetan ◽  
Ruohui Yang ◽  
Jerome Mertz
Keyword(s):  
Memory Effect ◽  
Phase Contrast ◽  
Differential Phase ◽  
Differential Phase Contrast
Sign in / Sign up

Export Citation Format

Share Document