Relative Intensities in ED Patterns From Thin Gold Films

1972 ◽  
Vol 30 ◽  
pp. 636-637
Author(s):  
R. H. Morriss ◽  
J. D. C. Peng ◽  
C. D. Melvin
Keyword(s):  
Theoretical Calculations ◽  
Diffraction Theory ◽  
Gold Films ◽  
Reasonable Accuracy ◽  
Experimental Conditions ◽  
Crystal Perfection ◽  
Heavy Atoms ◽  
Fine Focus ◽  
Convergent Beam ◽  
Beam Diffraction

Although dynamical diffraction theory was modified for electrons by Bethe in 1928, relatively few calculations have been carried out because of computational difficulties. Even fewer attempts have been made to correlate experimental data with theoretical calculations. The experimental conditions are indeed stringent - not only is a knowledge of crystal perfection, morphology, and orientation necessary, but other factors such as specimen contamination are important and must be carefully controlled. The experimental method of fine-focus convergent-beam electron diffraction has been successfully applied by Goodman and Lehmpfuhl to single crystals of MgO containing light atoms and more recently by Lynch to single crystalline (111) gold films which contain heavy atoms. In both experiments intensity distributions were calculated using the multislice method of n-beam diffraction theory. In order to obtain reasonable accuracy Lynch found it necessary to include 139 beams in the calculations for gold with all but 43 corresponding to beams out of the [111] zone.

Crystal Polarity Determination by Electron Channeling

2001 ◽  
Vol 7 (S2) ◽  
pp. 334-335
Author(s):  
J. Tafto
Keyword(s):  
Experimental Conditions ◽  
Electron Channeling ◽  
Structure Factors ◽  
Small Crystals ◽  
Polarity Determination ◽  
Convergent Beam ◽  
Interface Structures ◽  
Diffraction Effects ◽  
Beam Diffraction

Multilayers, heterostructures, nanostructures and composites are of great interest to the materials scientists, and frequently we encounter crystals lacking centrosymmetry. Thus crystal polarity determination on a microscopic scale is becoming increasingly important in describing interface structures and the internal defects in small crystals. in many cases the polarity of a crystallite can be determined by convergent beam electron diffraction, CBED. Powerful alternatives are to monitor the electron induced x-ray emission, EDS, or electron energy losses, EELS, under channeling conditions. While the determination of the phase of the structure factors, and thus the determination of the crystal polarity, relies on many beam diffraction effects when the CBED technique is used, two-beam experiments provide information about the phase of the structure factor when localized EDS or EELS signals are detected under channeling conditions.The experimental conditions used to determine the polarity and absolute orientation from electron channeling are similar to those used in ALCHEMI experiments to locate small amounts of atoms by electron channeling.

Energy-filtered convergent beam RHEED rocking curves from cleaved (100) surface of MgO

1991 ◽  
Vol 49 ◽  
pp. 626-627
Author(s):  
M. Gajdardziska-Josifovska ◽  
J. K. Weiss ◽  
J. M. Cowley
Keyword(s):  
Electron Diffraction ◽  
Theoretical Calculations ◽  
Diffraction Theory ◽  
High Energy ◽  
Energy Electron ◽  
Surface Structures ◽  
Low Energy Electron Diffraction ◽  
Surface Reconstructions ◽  
Low Energy Electron ◽  
Convergent Beam

Reflection high energy electron diffraction (RHEED) has been used extensively to observe changes in surface reconstructions by analyzing the geometry of the RHEED pattern and to monitor growth of layers in MBE systems by measuring the changes of the intensity of the specular spot with time. RHEED is also capable of yielding the structure of the surface by using dynamical diffraction theory to analyze experimental reflection rocking curves. These rocking curves trace the change in the intensity of the RHEED spots as a function of the angle of incident illumination. They are equivalent to the intensity vs. voltage curves (I-V) obtained in low energy electron diffraction (LEED) which have been used to determine most of the known surface structures. The LEED I-V curves are energy filtered and the theoretical calculations consider only the elastically-scattered electrons. The RHEED theory is also developed only for elastic scattering, but the experimental measurements so far have not been energy filtered.

Stress and Strain Measurements in Semiconductor Device Channel Areas by Convergent Beam Electron Diffraction

2006 ◽  
Vol 913 ◽  
Author(s):  
Jinghong Li ◽  
Anthony Domenicucci ◽  
Dureseti Chidambarrao ◽  
Brian Greene ◽  
Nivo Rovdedo ◽  
...  
Keyword(s):  
Semiconductor Device ◽  
Theoretical Calculations ◽  
Stress And Strain ◽  
Dislocation Loops ◽  
Strain Measurements ◽  
Stress Measurements ◽  
Strain Stress ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Good Agreement

AbstractConvergent electron beam diffraction (CBED) has been successfully applied to measure strain/stress in the channel area in PMOS semiconductor device with embedded SiGe (eSiGe) for 65nm technology. Reliable results of strain/stress measurements in the channel area have been achieved by good fitting of experimental CBED patterns with theoretical calculations. Stress measurements from CBED are in good agreement with simulations. A compressive stress as high as 823.9 MPa was measured in the <110> direction in the channel area of a PMOS device with eSiGe with 15% Ge and a thickness of 80nm. Stress measurements from CBED also confirm that the depth of the eSiGe and defects such as dislocation loops within the eSiGe relax strain/stress within the film and reduce strain/stress in the channel area.

Experimental Assessment of the Accuracy of Foil Thickness Measurements from Convergent-Beam Diffraction Patterns

1980 ◽  
Vol 38 ◽  
pp. 192-193
Author(s):  
Samuel M. Allen ◽  
Ernest L. Hall
Keyword(s):  
Measurement Errors ◽  
Diffraction Theory ◽  
Foil Thickness ◽  
Graphical Technique ◽  
Beam Approximation ◽  
Diffraction Patterns ◽  
Geometrical Factors ◽  
Convergent Beam ◽  
Thickness Measurements ◽  
Beam Diffraction

Convergent-beam electron diffraction (CBED) patterns can be analyzed to determine foil thickness by a simple graphical technique based on the two-beam approximation to dynamical diffraction theory. Errors incurred in such measurements are due to several causes, including: the effect of the two-beam approximation itself, measurement errors in analyzing the fringe positions in the patterns, and geometrical factors relating the thickness in the beam direction to the true foil thickness. This study was undertaken to determine typical errors that might be encountered in experimental applications of the technique.

Disappearance Voltage Determinations Using a Convergent Beam

1971 ◽  
Vol 29 ◽  
pp. 184-185
Author(s):  
W. L. Bell
Keyword(s):  
Second Order ◽  
Objective Method ◽  
Uniform Thickness ◽  
Rocking Curve ◽  
Crystal Perfection ◽  
Kikuchi Line ◽  
Central Maximum ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Technique

Disappearance voltages for second order reflections can be determined experimentally in a variety of ways. The more subjective methods, such as Kikuchi line disappearance and bend contour imaging, involve comparing a series of diffraction patterns or micrographs taken at intervals throughout the disappearance range and selecting that voltage which gives the strongest disappearance effect. The estimated accuracies of these methods are both to within 10 kV, or about 2-4%, of the true disappearance voltage, which is quite sufficient for using these voltages in further calculations. However, it is the necessity of determining this information by comparisons of exposed plates rather than while operating the microscope that detracts from the immediate usefulness of these methods if there is reason to perform experiments at an unknown disappearance voltage.The convergent beam technique for determining the disappearance voltage has been found to be a highly objective method when it is applicable, i.e. when reasonable crystal perfection exists and an area of uniform thickness can be found. The criterion for determining this voltage is that the central maximum disappear from the rocking curve for the second order spot.

“Preparation of Single Crystalline Gold Films for ED Studies”

1972 ◽  
Vol 30 ◽  
pp. 634-635
Author(s):  
Joseph D. C. Peng
Keyword(s):  
Crystal Morphology ◽  
Diffraction Theory ◽  
Scattering Matrix ◽  
Vacuum Evaporation ◽  
Gold Films ◽  
Matrix Formulation ◽  
Silver Films ◽  
Single Crystalline ◽  
Grating Pattern ◽  
Stacking Disorder

The relative intensities of the ED spots in a cross-grating pattern can be calculated using N-beam electron diffraction theory. The scattering matrix formulation of N-beam ED theory has been previously applied to imperfect microcrystals of gold containing stacking disorder (coherent twinning) in the (111) crystal plane. In the present experiment an effort has been made to grow single-crystalline, defect-free (111) gold films of a uniform and accurately know thickness using vacuum evaporation techniques. These represent stringent conditions to be met experimentally; however, if a meaningful comparison is to be made between theory and experiment, these factors must be carefully controlled. It is well-known that crystal morphology, perfection, and orientation each have pronounced effects on relative intensities in single crystals.The double evaporation method first suggested by Pashley was employed with some modifications. Oriented silver films of a thickness of about 1500Å were first grown by vacuum evaporation on freshly cleaved mica, with the substrate temperature at 285° C during evaporation with the deposition rate at 500-800Å/sec.

Transmission Scanning Electron Microscopy and Energy Analysis with the Siemens ELMISKOP 101

1972 ◽  
Vol 30 ◽  
pp. 450-451
Author(s):  
H. M. Thieringer
Keyword(s):  
Objective Lens ◽  
Transmission Microscopy ◽  
Image Recording ◽  
Mode Of Operation ◽  
Scanning Transmission ◽  
Electron Microscopes ◽  
And Performance ◽  
Convergent Beam ◽  
Ray Path ◽  
Beam Diffraction

It has repeatedly been show that with conventional electron microscopes very fine electron probes can be produced, therefore allowing various micro-techniques such as micro recording, X-ray microanalysis and convergent beam diffraction. In this paper the function and performance of an SIEMENS ELMISKOP 101 used as a scanning transmission microscope (STEM) is described. This mode of operation has some advantages over the conventional transmission microscopy (CTEM) especially for the observation of thick specimen, in spite of somewhat longer image recording times.Fig.1 shows schematically the ray path and the additional electronics of an ELMISKOP 101 working as a STEM. With a point-cathode, and using condensor I and the objective lens as a demagnifying system, an electron probe with a half-width ob about 25 Å and a typical current of 5.10-11 amp at 100 kV can be obtained in the back focal plane of the objective lens.

The Interpretation of Crystal Lattice Images

1972 ◽  
Vol 30 ◽  
pp. 550-551
Author(s):  
J. M. Cowley ◽  
Sumio Iijima
Keyword(s):  
Crystal Orientation ◽  
Diffraction Theory ◽  
Phase Changes ◽  
Electron Wave ◽  
Crystal Lattices ◽  
Heavy Atoms ◽  
Lattice Images ◽  
The Right ◽  
Intuitive Interpretation ◽  
Suitable Approximation

The imaging of detailed structures of crystal lattices with 3 to 4Å resolution, given the correct conditions of microscope defocus and crystal orientation and thickness, has been used by Iijima (this conference) for the study of new types of crystal structures and the defects in known structures associated with fluctuations of stoichiometry. The image intensities may be computed using n-beam dynamical diffraction theory involving several hundred beams (Fejes, this conference). However it is still important to have a suitable approximation to provide an immediate rough estimate of contrast and an evaluation of the intuitive interpretation in terms of an amplitude object.For crystals 100 to 150Å thick containing moderately heavy atoms the phase changes of the electron wave vary by about 10 radians suggesting that the “optimum defocus” theory of amplitude contrast for thin phase objects due to Scherzer and others can not apply, although it does predict the right defocus for optimum imaging.

Performance and applications of a field-emission gun TEM/STEM

1992 ◽  
Vol 50 (2) ◽  
pp. 942-943
Author(s):  
Judith M. Brock ◽  
Max T. Otten ◽  
Marc. J.C. de Jong
Keyword(s):  
Field Emission ◽  
High Resolution Imaging ◽  
High Quality ◽  
Small Energy ◽  
High Brightness ◽  
Small Probe ◽  
Resolution Imaging ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

A Field Emission Gun (FEG) on a TEM/STEM instrument provides a major improvement in performance relative to one equipped with a LaB6 emitter. The improvement is particularly notable for small-probe techniques: EDX and EELS microanalysis, convergent beam diffraction and scanning. The high brightness of the FEG (108 to 109 A/cm2srad), compared with that of LaB6 (∼106), makes it possible to achieve high probe currents (∼1 nA) in probes of about 1 nm, whilst the currents for similar probes with LaB6 are about 100 to 500x lower. Accordingly the small, high-intensity FEG probes make it possible, e.g., to analyse precipitates and monolayer amounts of segregation on grain boundaries in metals or ceramics (Fig. 1); obtain high-quality convergent beam patterns from heavily dislocated materials; reliably detect 1 nm immuno-gold labels in biological specimens; and perform EDX mapping at nm-scale resolution even in difficult specimens like biological tissue.The high brightness and small energy spread of the FEG also bring an advantage in high-resolution imaging by significantly improving both spatial and temporal coherence.

convergent-beam diffraction from surfaces

1987 ◽  
Vol 45 ◽  
pp. 30-33
Author(s):  
J. A. Eades ◽  
A. E. Smith ◽  
D. F. Lynch
Keyword(s):  
Reciprocal Lattice ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Three Dimensions ◽  
Plane Figure ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.

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