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Combined detector for BSE, SE and BSE+SE detection in a low voltage SEM
Autrata, Rudolf ; Jirák, Josef ; Romanovský, Vladimír ; Špinka, Jiří
Specimen observation at a low accelerating voltage of the electron beam (around 1kV) is a new and attractive technique of scanning electron microscopy. While detection to the signal of secondary electrons (SE) with the help of the scintillation-photomultiplier system described by Everhart-Thornley does not depend on the primary beam energy, the detection of backscattered electrons (BSE), having their energy only a bit lower than energy of the beam, is limited by a low sensitivity of semiconductor or channel plate detectors to channel plate detectors to electrons of energy below 2 keV.
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An ultrahigh vacuum scanning low energy electron microscope for surface studies
Müllerová, Ilona ; Frank, Luděk
In the course of recent six years, a complex device for examination of clean and well-defined surfaces with low energy electrons under ultrahigh vacuum conditions has been developed and put into operation. The apparatus is intended for exploration of novel image contrasts, available at landing energies of the scanning primary beam below 100 eV, under a residual pressure in the specimen vicinity in the order of 10.sup.-10./sup. mbar. The instrument consists of three vacuum chambers: the observation chamber, a chamber for in-situ preparations and the loading chamber of the air lock.
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Fully electrostatic low energy scanning electron column
Romanovský, V. ; El-Gomati, M. ; Frank, Luděk ; Müllerová, Ilona
The exploitation of low-energy electrons for examination of the material surfaces has several advantages. One of them is a small depth penetration of the primary electrons (PE) to the observed material. At low energies the charging effects on non-conductive or slightly conductive specimens are suppressed and also radiation damage of the observed specimen is decreased. Since the secondary electron (SE) yield is high, the signal to noise ratio (SNR) is about one order of magnitude larger than those in microscopes operated at 20kV.
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Secondary electron contrast of dopped regions in semiconductor - a matter of surface treatment?
Frank, Luděk ; Müllerová, Ilona ; El-Gomati, M.
Direct observation of doped patterns in semiconductor, usually on cleavedsections through multilayers but recently also in plan views of patterneddoping of a technological layer, is acquiring high interest because of its straightforward application in the semiconductor technology. Plenty of experimental data has been collected [1-4] from conventional SEM observation and recently first results showed improved contrasts attainable with specimen immersed into electric field. Main features are the sign of contrast- the p-type regions are always brighter than the n-type ones, and the contrast grows toward lower energies.
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Calculation of the beam profile
Oral, Martin
The beam profile provides local current density distribution of a particle beam. From the known distribution we can optimize the axial position of the specimen in a SEM, understand image aberrations or find optimum function of electron or ion analyzers. Graphical plot of the profile as a function of the z coordinate shows what is happening with the beam when it passes through the optical system. The first attempts of graphical presentationof the beam aberrations and profiles based on aberration theory are discussed in the recent diploma thesis.
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Misalignment aberrations
Dvořák, David
Misalignment aberrations arise from (small) imperfections of lens geometry - either because of the inaccuracy in the manufacturing of individual elements (like electrodes and/or pole-piece defects) or the misalignment of the optical elements in the system (tilted of shifted element). Under suchcircumstances the ideal symmetry is disturbed and additional parasitic fields are produced. In the effect they are producing additional image aberrations.
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Is this BEM useful for the computation of magnetic lenses?
Lencová, Bohumila
A new technique of boundary element method was proposed by Kasper in [1] under the title "An advanced boundary element method for the calculation of magnetic lenses"; see also the recent volume of AIEP [2]. What is new here? Obviously, for unsaturated lenses some of the formulas look a bit different than in [3] and the table in [1] is also different from that in [3].
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Accuracy of potential computations with FOFEM
Lencová, Bohumila
The first order finite element method (FOFEM) is often used for electron optical computations because of its ability to handle local dependence of material properties and complicated geometry of the electron optical elements. We use a topologically regular mesh based on irregular quadrilaterals. In order to avoid local computation error, we prefer to use meshes with a smoothly graded mesh step.
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