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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.
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Exposure Time Comparison between E-beam Writer with Gaussian Beam and Variable Shaped Beam
Horáček, Miroslav ; Krátký, Stanislav ; Urbánek, Michal ; Kolařík, Vladimír ; Meluzín, Petr ; Matějka, Milan ; Chlumská, Jana
One of the main goals in e-beam lithography is to increase exposure speed to achieve higher throughput. There are basically two types of electron-beam writers, shaped beam lithography systems and Gaussian beam lithography systems. The exposure time of both e-beam writers consist in essence of beam-on time, deflection system stabilization time and stage movement time. Exposure time testing was carried out on two types of patterns. There were completely filled in areas, binary period gratings (ratio 1:1 between exposed and unexposed areas), and multileveled structures (computer generated holograms). Exposures data was prepared according to standard technology (PMMA resist, exposure dose, non-alcoholic based developer) for both systems. The result of experiment shows that variable shaped beam system has advantage in multileveled structures while the Gaussian beam system is more suitable for gratings type of pattern. It was proved that combination of both systems has its use to increase exposures throughput.
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Plasmonic Structures In PMMA Resist
Urbánek, Michal ; Krátký, Stanislav ; Šimík, M. ; Kolařík, Vladimír ; Horáček, Miroslav ; Matějka, Milan
Some metal material can exhibit special physical phenomenon which is called plasmon resonance. This effect can be used in optical applications where designed structures, using this effect, have special function as optical filters, polarizers, holograms etc. This papers deals with preparation of plasmonic structures in poly(methyl methacrylate) (PMMA) resist which is the most common material used for e-beam processing. Designed structures were prepared by e-beam writer with Gaussian beam and accelerating voltage of 100 kV. These structures are usually prepared into negative tone resist hydrogen silsesquioxane (HSQ). We prepared these structures by unusual way into positive resist PMMA due to unavailability and cost of HSQ resist. By this way we are able to achieve high resolution of structures suitable for special optical application. Exposed structures were developed in isopropyl based developer. Final structures after development were coated by two metal layers (first one is Ag layer, second one is gold) by magnetron sputtering and vacuum evaporation. The quality of prepared plasmonic structures was examined by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM).
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