S. Mikmeková - Academia.edu (original) (raw)
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Papers by S. Mikmeková
Applied Physics Letters, 2012
ABSTRACT The reflectance of very slow electrons from solids and its electron energy dependence ar... more ABSTRACT The reflectance of very slow electrons from solids and its electron energy dependence are shown as characteristic for the crystal system and its spatial orientation so they can serve, e. g., to fingerprinting the orientation of grains in polycrystals. Measurements on single crystals and polycrystals are validated via electron backscatter diffraction analyses. Sensitivity of the method to fine details of crystallinity is demonstrated. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729879]
Materials, 2012
The high negative bias of a sample in a scanning electron microscope constitutes the "cathode len... more The high negative bias of a sample in a scanning electron microscope constitutes the "cathode lens" with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or even fractions of electronvolts with only slight readjustments of the column. Moreover, the field accelerates and collimates the signal electrons to earthed detectors above and below the sample, thereby assuring high collection efficiency and high amplification of the image signal. One important feature is the ability to acquire the complete emission of the backscattered electrons, including those emitted at high angles with respect to the surface normal. The cathode lens aberrations are proportional to the landing energy of electrons so the spot size becomes nearly constant throughout the full energy scale. At low energies and with their complete angular distribution acquired, the backscattered electron images offer enhanced information about crystalline and electronic structures thanks to contrast mechanisms that are otherwise unavailable. Examples from various areas of materials science are presented.
ABSTRACT The group of low energy electron microscopy at ISI AS CR in Brno has developed a methodo... more ABSTRACT The group of low energy electron microscopy at ISI AS CR in Brno has developed a methodology for very low energy scanning electron microscopy at high image resolution by means of an immersion electrostatic lens (the cathode lens) inserted between the illumination column of a conventional scanning electron microscope and the sample. In this way the microscope resolution can be preserved down to a landing energy of the electrons one or even fractions of an electronvolt. In the range of less than several tens of electronvolts the image signal generation processes include contrast mechanisms not met at higher energies, which respond to important features of the 3D inner potential of the target and visualise its local crystallinity as well as the electronic structure. The electron wavelength comparable with interatomic distances allows observation of various wave-optical phenomena in imaging. In addition, the cathode lens assembly secures acquisition of electrons backscattered from the sample at large angles with respect to the surface normal, which are abandoned in standard microscopes although they provide enhanced crystallinity information and surface sensitivity even at medium electron energies. The imaging method is described and illustrated with selected application examples.
Applied Physics Letters, 2012
ABSTRACT The reflectance of very slow electrons from solids and its electron energy dependence ar... more ABSTRACT The reflectance of very slow electrons from solids and its electron energy dependence are shown as characteristic for the crystal system and its spatial orientation so they can serve, e. g., to fingerprinting the orientation of grains in polycrystals. Measurements on single crystals and polycrystals are validated via electron backscatter diffraction analyses. Sensitivity of the method to fine details of crystallinity is demonstrated. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729879]
Materials, 2012
The high negative bias of a sample in a scanning electron microscope constitutes the "cathode len... more The high negative bias of a sample in a scanning electron microscope constitutes the "cathode lens" with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or even fractions of electronvolts with only slight readjustments of the column. Moreover, the field accelerates and collimates the signal electrons to earthed detectors above and below the sample, thereby assuring high collection efficiency and high amplification of the image signal. One important feature is the ability to acquire the complete emission of the backscattered electrons, including those emitted at high angles with respect to the surface normal. The cathode lens aberrations are proportional to the landing energy of electrons so the spot size becomes nearly constant throughout the full energy scale. At low energies and with their complete angular distribution acquired, the backscattered electron images offer enhanced information about crystalline and electronic structures thanks to contrast mechanisms that are otherwise unavailable. Examples from various areas of materials science are presented.
ABSTRACT The group of low energy electron microscopy at ISI AS CR in Brno has developed a methodo... more ABSTRACT The group of low energy electron microscopy at ISI AS CR in Brno has developed a methodology for very low energy scanning electron microscopy at high image resolution by means of an immersion electrostatic lens (the cathode lens) inserted between the illumination column of a conventional scanning electron microscope and the sample. In this way the microscope resolution can be preserved down to a landing energy of the electrons one or even fractions of an electronvolt. In the range of less than several tens of electronvolts the image signal generation processes include contrast mechanisms not met at higher energies, which respond to important features of the 3D inner potential of the target and visualise its local crystallinity as well as the electronic structure. The electron wavelength comparable with interatomic distances allows observation of various wave-optical phenomena in imaging. In addition, the cathode lens assembly secures acquisition of electrons backscattered from the sample at large angles with respect to the surface normal, which are abandoned in standard microscopes although they provide enhanced crystallinity information and surface sensitivity even at medium electron energies. The imaging method is described and illustrated with selected application examples.