On the high-frequency asymptotic evaluation of the potentials of elemental sources on an anisotropic impedance cylinder

Radio Science ◽  
1996 ◽  
Vol 31 (2) ◽  
pp. 389-399 ◽  
Author(s):  
Ronald J. Pogorzelski
Keyword(s):  
High Frequency ◽  
Asymptotic Evaluation ◽  
Impedance Cylinder

Asymptotic evaluation of high-frequency fields near a caustic: An introduction to Maslov's method

Radio Science ◽  
1984 ◽  
Vol 19 (4) ◽  
pp. 1001-1025 ◽  
Author(s):  
Richard W. Ziolkowski ◽  
Georges A. Deschamps
Keyword(s):  
High Frequency ◽  
Asymptotic Evaluation

RADIATION FROM A SOURCE NEAR A PLANE INTERFACE BETWEEN AN ISOTROPIC AND A GYROTROPIC DIELECTRIC

1964 ◽  
Vol 42 (11) ◽  
pp. 2153-2172 ◽  
Author(s):  
S. R. Seshadri ◽  
A. Hessel
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Surface Waves ◽  
High Frequency ◽  
Free Space ◽  
Line Source ◽  
Low Frequency ◽  
Plane Interface ◽  
Magnetic Current ◽  
Asymptotic Evaluation

The radiation from a line source of magnetic current situated in free space near a plane interface between a semi-infinite free space and a semi-infinite gyrotropic dielectric is investigated for the case in which the gyrotropic axis is parallel to the line source. In addition to the space waves, it is found that in general two unidirectional surface waves are excited along the interface. The dispersion relations for the space and the surface waves are thoroughly examined. Both surface waves have different high-frequency cutoff but no low-frequency cutoff. The characteristics of these surface waves are investigated. An asymptotic evaluation of the total electromagnetic field is carried out for a particularly simple choice of the source frequency. For this frequency, the dependence of the efficiency of excitation of the surface waves on the distance of the source from the interface is determined. The radiation patterns are plotted for various values of the static magnetic field and the position of the source.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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