A study of the (00) LEED beam intensity at normal incidence from CdS(0001), Cu(001), Cu(111), and Ni(111)

L.R. Bedell; H.E. Farnsworth

doi:10.1016/0039-6028(74)90302-1

Systematic Reflections and the Two Beam Concept of Extinction Distance

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061677 ◽

1967 ◽

Vol 25 ◽

pp. 332-333

Author(s):

S. S. Sheinin ◽

C. D. Cann

Keyword(s):

Dynamical Theory ◽

Beam Intensity

The effects of systematic reflections on the variation of diffracted beam intensity with depth in a crystal can only be taken into account by using the multi-beam dynamical theory. The results of calculations of this kind, which are presented here, indicate that the intensity profiles obtained are not periodic. Since extinction distance is a concept strictly applicable only when the diffracted beam intensity varies periodically with depth, its use as a parameter in describing multi-beam intensity profiles must be carefully considered.

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Analysis of Contrast Reversal in SEM Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009525x ◽

1972 ◽

Vol 30 ◽

pp. 398-399

Author(s):

M. D. Coutts ◽

E. R. Levin

Keyword(s):

Incident Beam ◽

Normal Incidence ◽

Beam Current ◽

Secondary Emission ◽

Image Contrast ◽

Sem Images ◽

Secondary Electrons ◽

Image Position

On tilting samples in an SEM, the image contrast between two elements, x and y often decreases to zero at θε, which we call the no-contrast angle. At angles above θε the contrast is reversed, θ being the angle between the specimen normal and the incident beam. The available contrast between two elements, x and y, in the SEM can be defined as,(1)where ix and iy are the total number of reflected and secondary electrons, leaving x and y respectively. It can easily be shown that for the element x,(2)where ib is the beam current, isp the specimen absorbed current, δo the secondary emission at normal incidence, k is a constant, and m the reflected electron coefficient.

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Characterization of Rh/Si multilayer structure by HREM and HAADF

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121016 ◽

1992 ◽

Vol 50 (1) ◽

pp. 122-123

Author(s):

Y. Cheng ◽

J. Liu ◽

M.B. Stearns ◽

D.G. Steams

Keyword(s):

Normal Incidence ◽

High Resolution Electron Microscopy ◽

X Rays ◽

Beam Direction ◽

Cross Sectional ◽

Optical Elements ◽

Resolution Electron ◽

Point To Point ◽

Better Than

The Rh/Si multilayer (ML) thin films are promising optical elements for soft x-rays since they have a calculated normal incidence reflectivity of ∼60% at a x-ray wavelength of ∼13 nm. However, a reflectivity of only 28% has been attained to date for ML fabricated by dc magnetron sputtering. In order to determine the cause of this degraded reflectivity the microstructure of this ML was examined on cross-sectional specimens with two high-resolution electron microscopy (HREM and HAADF) techniques.Cross-sectional specimens were made from an as-prepared ML sample and from the same ML annealed at 298 °C for 1 and 100 hours. The specimens were imaged using a JEM-4000EX TEM operating at 400 kV with a point-to-point resolution of better than 0.17 nm. The specimens were viewed along Si [110] projection of the substrate, with the (001) Si surface plane parallel to the beam direction.

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Divergent beam microanalysis studies of bimetallic platinum catalysts supported on γ-AL2O3

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138518 ◽

1995 ◽

Vol 53 ◽

pp. 428-429

Author(s):

JR Fryer ◽

Z Huang ◽

D Stirling ◽

G. Webb

Keyword(s):

Dead Time ◽

Platinum Catalysts ◽

Beam Intensity ◽

Beam Diameter ◽

Divergent Beam ◽

Bimetallic Systems ◽

Reforming Catalyst ◽

Before And After ◽

Individual Particles

Platinum dispersed on γ-alumina is used as a reforming catalyst to convert linear hydrocarbons to cyclic aromatic products. To improve selectivity and lifetime of the catalyst, other elements are included, and we have studied the distributions of Pt/Re, and Pt/Sn, bimetallic systems on the support both before and after use in octane reforming. Often, one or both of the components are not resolvable by HREM or microanalysis as individual particles because of small size and lack of contrast on the alumina, and divergent beam microanalysis has been used to establish the presence and relationship between the two elements.In the majority of catalysts the platinum is in the form of small panicles, some of which are large enough to be resolvable in the microscope. The ABT002B microscope with Link windowless Pentafet detector, used in this work, was able to obtain a resolvable signal from particles of 2nm diameter upwards. When the beam was concentrated on to such a particle the signal was at a maximum, and as the beam diameter was diverged - at the same total beam intensity and dead time - the signal decreased as shown in Figure 1.

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On resolving fine periodic microstructures in the optical microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153798 ◽

1989 ◽

Vol 47 ◽

pp. 364-365

Author(s):

W.S. Putnam ◽

C. Viney

Keyword(s):

Liquid Crystalline ◽

Numerical Aperture ◽

Polarized Light ◽

Normal Incidence ◽

Optical Microscope ◽

Angle Of Incidence ◽

Resolution Limit ◽

Crystalline Materials ◽

Periodic Microstructures ◽

Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

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Microspectroscopy Using a Solid Immersion Lens

Microscopy and Microanalysis ◽

10.1017/s1431927600026817 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 148-149

Author(s):

C.D. Poweleit ◽

J Menéndez

Keyword(s):

Spatial Resolution ◽

Focal Plane ◽

Numerical Aperture ◽

Normal Incidence ◽

Spot Size ◽

Index Of Refraction ◽

Objective Lens ◽

Improvement Factor ◽

Oil Immersion ◽

Long Time

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.

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