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Studies of biological specimens by environmental scanning electron microscopy
Autrata, Rudolf ; Horký, D. ; Ilkovics, L. ; Procházka, V. ; Skřička, T.
Environmental scanning electron microscopy (ESEM) is a technique which permits observation of the surfaces of biological materials under conditions close to natural environments. The quality of surface images was studied in specimens obtained from solid plant and insect tissues and from human and laboratory animal tissues collected by biopsy from the digestive and urinary systems. For specimen preparation, several methods were used and the results of observations by ESEM and conventional scanning electron microscopy (SEM) were compared to find out the approach which gave the best images in each biological material. In some cases, a modified procedure was used.
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Scanning electron microscopy at low vacuum in specimen chamber
Autrata, Rudolf ; Jirák, Josef
Observation of specimens at a low vacuum in the specimen chamber brings some advantages in comparison with observation in a high vacuum. Water-containing and electrically non-conductive specimens are of special significance. The principle of low vacuum microscopes and problems with the interaction of electrons with the gaseous medium are described. Detection of signals in the so-called environmental (low vacuum) microscope is realised with the help of a single crystal YAG scintillation detector of backscattered electrons on which an electrode system for ionisation detection of secondary electrons is deposited. Some examples of insulation specimens, wet specimens and biological specimens of soft tissues are presented.
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Scanning low and very low energy electron microscopy
Müllerová, Ilona ; Frank, Luděk
The main aspects of the SEM performed in the low energy (below 5 keV) and very low energy (below 50 to 100 eV) ranges are briefly summarised. They include the necessity to vary the beam energy along the column, in order to suppress the energy dependence of the resolution, and to tune the compromise between the resolution and the field on the specimen surface. Applications under "normal" vacuum conditions are mentioned.
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New CAD program for design in electron optics
Lencová, Bohumila ; Zlámal, J.
When designing electron or ion optical systems, the FEM has found applications not only in the magnetic lens design but also in the design of electrostatic lenses and deflection systems. The first order FEM can provide accurate results not only on the axis but also off axis and thus suitable for ray tracing. Computations run on personal computers that are getting ever faster and with improving graphical capabilities. Important development has also been made in the operating systems, 32 bit Windows being rather standard. The new compilers for PCs for most languages including Fortran run under Windows, example being Compaq Visual Fortran that we use not only for "console" applications (few GByte can be addressed) but also for graphics. Graphics is important for any design that involves input or modifications of geometry and display of results.
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Computations of Wien Filter Properties and Aberrations
Lencová, Bohumila ; Vlček, Ivan
Wien filter is studied in electron optics as a separator in a LEEM or as a separator of primary and secondary beams in a low voltage SEM. The advantage of the Wien filter is that one beam is only slightly influenced by the filter and the second beam can easily be handled, the required separation angle for this is about 10-20 degrees. The computation of aberrations of the Wien filter needs to take into account field shapes of both strong dipole fields and the additional quadrupole, the action of the filter is then that of a weak lens and the aberation structure is more complicated than that of a rotationally symmetric lens. The determination of aberation coefficients from direct ray tracing for this optical element is often preferred to aberration theory.
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Dimension measurement in a cathode lens equipped low-energy SEM
Hutař, Otakar ; Oral, Martin ; Müllerová, Ilona ; Frank, Luděk
The paper deals with calibration of magnification in a cathode lens equipped SEM, which provides a high resolution in the energy range below 2000 eV, where both the charging-up and edge effect phenomena, complicating the measurement of dimensions, are suppressed. An analytical expression for the image magnification, in the dependence on the electron impact energy and the working distance, is derived and verified with respect to the measured values. Finally, a procedure suitable for the routine calibration is proposed.
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