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Analysis and modification of thin layers using ion beams
Jonner, Jakub ; Lörinčík, Jan (referee) ; Bábor, Petr (advisor)
This diploma thesis deals with analysis and modification of thin layers using ion beams. The first part of this diploma thesis deals with phenomena accompanying ion beam bombardment of solid matter. The second part of this diploma thesis is concerned with Secondary Ion Mass Spectroscopy (SIMS) and Low Energy Ion Scattering (LAIS). This work convey some basic information about these two techniques and it also deals with some benefits result in their connection into parallel depth profiling mode (such as better depth resolution of the LEIS profile, quantification of the SIMS). These benefits are demonstrated on MoSi film measurement. Within the framework of this thesis a new UHV manipulator was designed. This new UHV manipulator is equipped with precise stepper UHV motor and since the proportions are smaller, the manipulation with a sample in a space limited UHV chamber is much more comfortable and more precise. The third part of this diploma thesis deals with ion-beam induced transformation of epitaxially grown Fe films with thickness of 22 monolayer (ML) and 44 ML on Cu(100) single crystal at room temperature. Metastable Fe films of 22 ML thickness were prepared in CO pressure and 44 ML Fe films were prepared by co-evaporation of Fe with Fe64Ni36 (invar). Structural changes are analyzed by scanning tunneling microscopy and low-energy electron diffraction. The aim of this thesis is to discuss the influence of the sputtering parameters such as ion dose and ion energy on the nucleation of bcc nanocrystals, their growth, final shape and size. The influence of different Ni concentration on stability of 44 ML thick Fe films is also discussed.
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Upgrade of the UHV manipulator for SIMS and LEIS methods
Dao, Tomáš ; Polčák, Josef (referee) ; Bábor, Petr (advisor)
This bachelor’s thesis deals with the design and the construction of the manipulator, which operates under ultra high vacuum. In the first section, the original design and realization of the manipulator with six motion axis is introduced. Second section deals with the modifications of the manipulator. Advantages and disadvantages of the design are discussed and a new design of the manipulator, based on the experience from manipulator operation, is projected. Section is mainly focused on the design of the sample rotation using a stepper motor working in the ultra high vacuum. The new Faraday cup was also designed and tested. The last section contains the LEIS structural analysis measurement using the manipulator.
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Initial Stage of Mutual Diffusion of Carbide in Iron
Čermák, Jiří ; Král, Lubomír
Initial stage of mutual diffusion close to carbon/iron interface was investigated in the present work. SIMS technique of concentration profiles enabled to study the carbon redistribution in the very early stages, when the diffusion process occurs – at least partly – in regions, where the carbon concentration exceeds the carbon concentration limit. It was observed that carbon diffusion coefficients are much lower under such conditions, than in Fe matrix with equilibrium carbon concentration. The measured carbon diffusion coefficients approached values reported for carbon diffusion in carbides.
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Measurement of Carbon Diffusion Coeficient - Calibration of Sputter Depth
Král, Lubomír ; Čermák, Jiří
Depth profiling mode of MiniSIMS device was applied to diffusion measurement. Calibration of crater depth was done using shearing interference microscope Zeiss Epival Interphako (ZEI) and confocal mikroskope Olympus LEXT OLS3100 with atomic force microscopy (AFM) modul. The ZEI uses one of the classical interferometric measuring methods. Generally this method leads to results with considerable experimental error. AFM is a very high-resolution type of scanning probe microscopy, with typical resolution of the order of fractions of nanometers, which is more than 1000 times better than the optical diffraction limit. However, the results taken by ZEI were in agreement with much more precise results of surface profiling achieved by AFM. It was found, at given experimental conditions (Fe-rich matrix, Ga + primary ions, 5 kV/3nA, DWT=1), that the sputter rate is some 0.3 nm per a single sputter scan of the crater area (50x50 µm). This depth calibration with SIMS technique can be applied to the study of carbon diffusion in BCC iron as an example. Special technique was developed, which avoids radio-tracer measurements with C-14. Obtained results are lower than the extrapolated values, which may be due to limited solubility of carbon in iron.
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Low-temperature diffusion of carbon in iron measured by SIMS technique
Čermák, Jiří ; Král, Lubomír
Depth profiling mode of MiniSIMS device was applied to diffusion measurement. As an example, carbon diffusion in BCC iron was studied. There are sparse experimental diffusion data at temperatures below the eutectic horizontal (996 K). This is caused by the fact that direct measurement of carbon diffusion coefficient in ferrite at low temperatures is complicated by very low solubility of carbon. For practical purposes, the extrapolation of high-temperature data to low temperature region is usually used for estimation of diffusioncontrolled kinetics in ferrite alloys. Present work has shown that the SIMS technique can be applied to the study of carbon diffusivity in iron. Special technique was developed, which avoids radio-tracer measurements with C-14. Obtained results are lower than the extrapolated values, which may be due to limited solubility of carbon in iron.
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Properties of Bi LMIS with ion clusters
Radlička, Tomáš
The ion beams used in SIMS are produced by liquid–metal ion sources (LMIS) which provide fine, optically bright ion beams even for low emission currents around 1 .mu.A or less. The typical energy of the primary beam varies from 10 to 40 keV. The properties of the LMIS are strongly limited by the effect of the Discrete Coulomb Interactions (DCI) near the source. The DCI increase the energy width (Boersh effect) and decrease the brightness of the source due to the trajectory displacement effect. Contrary to the Ga LMIS which contains mostly only Ga+ ions, in case of the Bi LMIS the ion beam consists of several ion types and clusters of ions with similar currents. Because each ion type has different charge and mass they will be accelerated to different velocities, which increase the number of interactions and decreases the quality of the source. The aim of this contribution is a simulation of the effect of the clusters on the source properties based on the MC simulation.
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