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Transmission mode in scanning low enery electron microscope
Müllerová, Ilona ; Hovorka, Miloš ; Frank, Luděk
We incorporated the cathode lens (CL) principle, well known from the emission microscope, to the SEM in order to operate at very low landing energies. The primary beam electrons of several keV are decelerated to nearly zero energy of landing on the specimen negatively biased to high potential. Reflected electrons are collected on a grounded detector situated above the sample but the same can be done below the sample of a fair transparency for electrons. High collection efficiency and high amplification of both detectors is secured thanks to the cathode lens field. We use a scintillation detector for the reflected mode and a semiconductor structure for the transmitted electron (TE) mode. In this arrangement resolution of few nm is obtainable across the full energy range.
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Prospects of the scanning low energy electron microscopy in materials science
Mikmeková, Šárka ; Hovorka, Miloš ; Konvalina, Ivo ; Müllerová, Ilona ; Frank, Luděk
The use of the scanning low energy electron microscopy (SLEEM) has been slowly making its way into the field of materials science, hampered not by limitations in the technique but rather by the relative scarcity of these instruments in research institutes and laboratories. Various techniques exist which are capable of studying the material microstructure, with the scanning electron microscopy (SEM), (scanning) transmission microscopy ((S)TEM) and focused ion beam (FIB) microscopy being perhaps the most known. A specific way to visualizing the microstructure of materials at high spatial resolution, to achieve a high contrast between grains in polycrystals and very fast data acquisition is to use the cathode lens (CL) mode in SEM. The CL mode in the SEM enables us to detect slow but not only slow, high angle scattered electrons that carry mainly crystallographic contrast based on the electron channeling, mostly in the Mott scattering angular range.
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Imaging of dopants under presence of surface ad-layers
Mika, Filip ; Hovorka, Miloš ; Frank, Luděk
Scanning electron microscopy is widely used for imaging of semiconductor structures. Image contrast between differently doped areas is observable in the secondary electron emission. Quantitative relation exists between the image contrast and the dopant concentration. However, further examination has shown the dopant contrast level of low reproducibility and dependent on additional factors like the primary electron dose, varying energy and angular distributions of the SE emission and also presence of ad-layers on the semiconductor surface.
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Optical and scanning electron microscopies in examination of ultrathin foils
Konvalina, Ivo ; Hovorka, Miloš ; Fořt, Tomáš ; Müllerová, Ilona
Very low energy scanning transmission electron microscopy is emerging as a novel tool for examination of ultrathin foils to learn more about the electron structure of solids. The electron micrographs provide image contrasts governed by the effective thickness of the sample proportional to the inner potential and at lowest energies the local density of electron states in the direction of impact of the electron wave starts to dominate. The optical methods are used during the sample preparation. The laser confocal microscope Olympus Lext OLS 3100 was used for preliminary observations of the 3 nm C foil prepared by magnetron sputtering in nitrogen atmosphere on a flat glass covered by a disaccharide layer.
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Mapping of dopants by electron injection
Hovorka, Miloš ; Konvalina, Ivo ; Frank, Luděk
Dopants in silicon structures locally modify the secondary electron emission, revealing in this way their distribution over the sample. Primary electron beam with energy around 1 keV is usually used for probing the doped structures. However, very low landing energy range has proved itself an efficient tool for mapping dopants in semiconductors.
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