On-line measurement of specimen thickness by Convergent Beam Electron Diffraction

1990 ◽  
Vol 48 (2) ◽  
pp. 480-481
Author(s):  
Max T. Otten
Keyword(s):  
Electron Diffraction ◽  
Thickness Measurement ◽  
Dark Field ◽  
Convergent Beam Electron Diffraction ◽  
Specimen Thickness ◽  
Bright Field ◽  
Beam Electron ◽  
Kikuchi Line ◽  
On Line ◽  
Convergent Beam

Convergent Beam Electron Diffraction (CBED) thickness measurement is the easiest and most accurate way of determining the thickness of crystalline materials. The method was described by Kelly et al. The specimen thickness can be calculated from a few measurements on a recorded diffraction pattern in a matter of minutes (by hand) or seconds (by a computer program).For thickness measurement a CBED pattern is needed that contains a two-beam diffracting condition, with a dark Kikuchi line going through the centre of the Bright-Field disc and the corresponding bright Kikuchi line through the centre of a Dark-Field disc. Parallel to the bright Kikuchi line, the Dark-Field disc contains a number of fringes (Fig. 1) whose distance from the Kikuchi line varies with specimen thickness. The data needed for a measurement are the electron wavelength, the d-spacing dhkl of the diffraction used, the distance 2θB between the Bright-Field disc and Dark-Field disc in the CBED pattern, and the distances Δθi between the dark thickness fringes and the bright Kikuchi line in the Dark-Field disc (Fig. 2).

Anaysis of Lacbed Patterns from A Microtwin in Cobalt

2001 ◽  
Vol 7 (S2) ◽  
pp. 266-267
Author(s):  
Hwang Su Kim ◽  
Byung Ryang Ahn
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Stacking Faults ◽  
Dark Field ◽  
Convergent Beam Electron Diffraction ◽  
Bright Field ◽  
Beam Electron ◽  
Thin Foils ◽  
Specimen Height ◽  
Convergent Beam

Recently LACBED (Large Angle Convergent Beam Electron Diffraction) studies for identifying the nature of stacking faults has been reported in [1,2]. Here we report the LACBED study for a microtwin whose images are usually similar to those of an intrinsic or an extrinsic stacking faults (for this discussion, see [3]).Observations: Thin foils of cobalt with the thickness of about 180 nm (f.c.c phase, a=0.354 nm) were examined by a Philips CM200. Fig. 1 shows strong beam dark field images of microtwins or stacking faults. Fig. 2 shows the bright field LACBED pattern taken near the area marked as a circle in fig. 1. The specimen height, from the convergent point of beams, was about 0.0586 mm and the convergent angle was 0.615 degrees.Calculations and analysis: Analysis of fig. 1 alone indicates the encircled fault an extrinsic stacking fault.

Burgers Vector Analysis of Vertical Dislocations in Ge Crystals by Large-Angle Convergent Beam Electron Diffraction

2015 ◽  
Vol 21 (3) ◽  
pp. 637-645 ◽  
Author(s):  
Heiko Groiss ◽  
Martin Glaser ◽  
Anna Marzegalli ◽  
Fabio Isa ◽  
Giovanni Isella ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Dark Field ◽  
Convergent Beam Electron Diffraction ◽  
Vector Analysis ◽  
Burgers Vector ◽  
Beam Electron ◽  
Convergent Beam

AbstractBy transmission electron microscopy with extended Burgers vector analyses, we demonstrate the edge and screw character of vertical dislocations (VDs) in novel SiGe heterostructures. The investigated pillar-shaped Ge epilayers on prepatterned Si(001) substrates are an attempt to avoid the high defect densities of lattice mismatched heteroepitaxy. The Ge pillars are almost completely strain-relaxed and essentially defect-free, except for the rather unexpected VDs. We investigated both pillar-shaped and unstructured Ge epilayers grown either by molecular beam epitaxy or by chemical vapor deposition to derive a general picture of the underlying dislocation mechanisms. For the Burgers vector analysis we used a combination of dark field imaging and large-angle convergent beam electron diffraction (LACBED). With LACBED simulations we identify ideally suited zeroth and second order Laue zone Bragg lines for an unambiguous determination of the three-dimensional Burgers vectors. By analyzing dislocation reactions we confirm the origin of the observed types of VDs, which can be efficiently distinguished by LACBED. The screw type VDs are formed by a reaction of perfect 60° dislocations, whereas the edge types are sessile dislocations that can be formed by cross-slips and climbing processes. The understanding of these origins allows us to suggest strategies to avoid VDs.

The Art and Application of Large Angle Convergent Beam Electron Diffraction

2012 ◽  
Vol 186 ◽  
pp. 16-19 ◽  
Author(s):  
Elżbieta Jezierska
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Antiphase Boundary ◽  
Antiphase Domain ◽  
Dark Field ◽  
Convergent Beam Electron Diffraction ◽  
Intermetallic Alloys ◽  
Beam Electron ◽  
Transmission Electron ◽  
Convergent Beam

The antiphase domain structure in Ni3Al and Al3Ti+Cu intermetallic alloys was recognized by conventional transmission electron microscopy and large angle convergent beam electron diffraction methods. In the case of antiphase boundary the superlattice excess line is split into two lines with equal intensity on bright and dark field LACBED pattern. This splitting can be considered as typical and used to identify APBs. The recognition between perfect structure of the defect-free matrix and the screw deviation around the nanopipes in GaN epilayers was performed with high accuracy using Zone Axis LACBED images.

scholarly journals Comparison of convergent beam electron diffraction and annular bright field atomic imaging for GaN polarity determination

2016 ◽  
Vol 32 (5) ◽  
pp. 936-946 ◽  
Author(s):  
Alexana Roshko ◽  
Matt D. Brubaker ◽  
Paul T. Blanchard ◽  
Kris A. Bertness ◽  
Todd E. Harvey ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Bright Field ◽  
Beam Electron ◽  
Polarity Determination ◽  
Image Position ◽  
Convergent Beam

Abstract

Computer experiments for coherent convergent-beam electron diffraction

1983 ◽  
Vol 41 ◽  
pp. 304-305
Author(s):  
William Krakow
Keyword(s):  
Electron Diffraction ◽  
Amorphous Materials ◽  
Three Dimensional ◽  
Computer Experiments ◽  
Convergent Beam Electron Diffraction ◽  
Specimen Thickness ◽  
Beam Electron ◽  
Wide Range ◽  
Stem Type ◽  
Convergent Beam

Considerable effort has been expended to use convergent beam electron diffraction (CBED) from small specimen areas with an incoherent thermionic source. Here space group classification and even three dimensional analysis have proven to be possible by observing the diffraction disks and the fine detail seen within these disks. The use of a coherent convergent beam has been attempted for a field emission STEM type instrument and a number of novel interference effects have recently been observed in both crystalline and amorphous materials. Preliminary CBED computer calculations were performed for a dislocation in Si3 however no structural detail was observed in the diffraction disks because the computation only considered a 30Å thick crystal. Computations covering a wide range of materials, specimen thickness values and STEM type probe conditions has been obtained by the present author. In these papers only results for zone axis patterns and 100kV electrons were given. It is now the intent to present some new results at high voltages (200kV) and for non-symmetric crystal orientations and with larger reciprocal space sampling distributions

On-Line Measurement of Foil Thickness from Convergent Beam Electron Diffraction Patterns

1982 ◽  
Vol 40 ◽  
pp. 694-695
Author(s):  
J. Bentleyt ◽  
G. L. Lehman
Keyword(s):  
Electron Diffraction ◽  
Materials Science ◽  
Convergent Beam Electron Diffraction ◽  
Foil Thickness ◽  
Beam Electron ◽  
Line Measurement ◽  
On Line ◽  
Graphical Technique ◽  
Diffraction Patterns ◽  
Convergent Beam

Accurate values of foil thickness are required in many materials science applications, such as for measurement of defect concentrations and for x-ray microanalysis absorption corrections. Kelly et al. demonstrated that convergent beam electron diffraction (CBED) patterns can be analyzed using a simple graphical technique to give values for foil thickness with ±2% accuracy. More recently, Allen extended the treatment to make use of both maxima and minima in the CBED disks. The technique requires a knowledge of the d-spacing of the reflection, the electron wavelength, an evaluation of the deviation parameter, si, associated with the i-th fringe in the diffracted beam disk, and the assignment of a set of constants to "index" the fringes.

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