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Deformation of thin self-standing mask at inhomogeneous irradiation.
Koláček, Karel ; Schmidt, Jiří ; Frolov, Oleksandr ; Štraus, Jaroslav ; Chalupský, Jaromír ; Choukourov, A.
Flatness of the mask is one of key features influencing the quality of image. Among factors that can affect mask flatness belongs inhomogeneous illumination. This does not apply to lithography, but to experiments that use only discrete parts of mask e.g. for nanostructuring or other type of material research. It is shown that even single EUV laser shot (laser wavelength ~46.9 nm, pulse duration ~1.5 ns, focused pulse energy ~20 .mu.J, peak fluency 48 J/cm2) not only deforms the mask, but also changes mask-substrate distance. In our case two kinds of grids (one circular with rectangular windows 7.5x7.5 μm and bars 5 micro m (period 12.5x12.5 micro m), other rectangular with rectangular windows 3.2x1.2 μm and bars 0.8 micro m (period 4x2 micro m)) were attached to PMMA substrate and exposed to one or five superimposed focused laser shots. The mask (grid) deformation was inferred from the changes of diffraction pattern engraved into PMMA.
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Density matrix renormalization group calculations and entanglement optimization in quantum chemistry
Antalík, Andrej ; Pittner, Jiří (advisor) ; Chalupský, Jaromír (referee)
Density matrix renormalization group is a powerful numerical approach originating in solid state physics. Since its introduction to quantum chemis- try it has been successfully applied to many challenging problems and proved especially efficient for systems with strong multi-reference character. As the method is not invariant to the change of orbital ordering, we implemented the automatic orbital ordering optimization procedure built around the entan- glement analysis and employing the Fiedler method. A technique for active space selection based on one-orbital entropy is introduced. We followed the study by Berardo et al. in which EOM-CC methods were applied to excited states of TiO2 clusters. Four lowest-lying singlet excited states of monomer, dimer and trimer were calculated by means of the DMRG method. In case of the monomer there was good agreement for two states, but the calculations suffered from insufficient treatment of dynamic correlation. For the dimer our results were in very good agreement with EOM-CCSDT results and for the trimer further study would be appropriate. 1
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Generation of short-wavelength (<160 nm) radiation by conventional lasers
Chalupský, Jaromír ; Malý, Petr (advisor) ; Krása, Josef (referee)
The theoretical part of this diploma thesis seeks to explain the methods used for generation of coherent short-wavelength radiation. It describes the principles and the operation conditions of direct laser sources and indirect coherent radiation sources based on non-linear effects. Special attention is then paid to the short-wavelength free-electron lasers. This work summarizes properties of numerous sources of this kind. The introductory part of the thesis deals with the physical background of the generation and the manipulation of shortwavelength (VUV/XUV) radiation. The experimental part gives a summary of the results obtained at the FLASH facility (Free Electron LASer in Hamburg; earlier known as VUV FEL) operated at DESY. Methods and instrumentation used for investigating the materials damage due to laser ablation are described in this part of the thesis. UV-vis emission spectra of ablation plume were measured. Main goal is here to determine the ablation thresholds and the effective atenuation lengths in poly (methyl methacrylate) (PMMA), quartz (a-SiO2) and monocrystalline silicon irradiated with pulsed (~30fs) short-wavelength (32nm) intense laser radiation.
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