Národní úložiště šedé literatury Nalezeno 4 záznamů.  Hledání trvalo 0.00 vteřin. 
Transmission of very slow electrons as a diagnostic tool
Frank, Luděk ; Nebesářová, Jana ; Vancová, Marie ; Paták, Aleš ; Mikmeková, Eliška ; Müllerová, Ilona
The penetration of electrons through solids is retarded by sequences of their interactions with the matter in which the electron changes its direction of motion and loses its energy. Inelastic collisions, the intensity of which reaches a maximum at around 50 electronvolts (eV) and drops steeply on both sides of this fuzzy threshold, are decisive for the penetration of electrons. Transmission microscopy (TEM or STEM) observes thin samples of tens to hundreds of nanometres in thickness by passing electrons of energies of tens to hundreds of kiloelectronvolts through them. The range below 50 eV has recently been utilized in the examination of surfaces with reflected electrons, where high image resolution is achieved thanks to the retardation of electrons close to the sample surface in the ´cathode lens´ . In this lens, the role of the cathode is played by the sample itself, biased to a high negative potential. This principle can also be utilized in the transmission mode with samples of a thickness at and below 10 nm. This method has recently been implemented and verified on graphene samples prepared by various methods. The results have made it possible to diagnose the continuity and quality of the graphene flakes. Furthermore, series of experiments have been performed involving the observation of ultrathin tissue sections with electrons decelerated to about 500 eV and less, where they provide an image contrast of the cell ultrastructure much higher than that provided by traditional microscopic modes.
Examination of Graphene with Very Slow Electrons
Mikmeková, Eliška ; Frank, Luděk
Although graphene has been available and intensively studied for nearly a full decade, new methods are still required for its examination and diagnostics. Even checking the continuity of layers and the reliable counting of layers of graphene and other 2D crystals should be easier to perform. Scanning electron microscopy with slow and very slow electrons offers an innovative tool enabling one to see graphene samples at nanometer or even sub-nanometer lateral resolution in both transmitted and reflected electrons and to count the number of layers reliably in both imaging modes. Diagnostics can be performed in this way on freestanding graphene samples as well as on graphene grown on the surfaces of bulk substrates. Moreover, bombardment with very slow electrons acts as an ultimate cleaning procedure removing adsorbed gases from crystal surfaces which can be monitored in scanned transmission electron images taken at below 50 eV.
Computer controlled SEM Tesla BS 350 with cathode for detection of slow and Auger electrons
Hrnčiřík, Petr
The goal of the experiment is an in-situ comparison of the signals given by Auger and by slow electrons (down to 10 eV) with a high resolution. These open new possibilities of getting information about the material and topographical contrast from real surfaces. A new experimental device was designed for this intention, which is presented in this contribution.
Examination of semiconductor structures with slow electrons
Frank, Luděk ; Müllerová, Ilona
Possibilities for visualization of the doped areas and variances in the local density of electron states are briefly reviewed. First examples are presented of utilizing very slow electrons in a cathode lens equipped SEM for this purpose. These include acquisition of the doping contrast via secondary electrons and observation of the local energy band structure by means of elastically backscattered electrons.

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