|
|
Physically chemical properties of epitaxial films CeO2/Cu(110)
Aulická, Marie ; Veltruská, Kateřina (advisor) ; Nehasil, Václav (referee)
In this work ways of preparation of thin epitaxial cerium oxide film on Cu(110) surface were studied. X-ray photoelectron spectroscopy (XPS), X-ray photoelectron difraction (XPD), low energy electron difraction (LEED), ion scattering spectroscopy (ISS) and scanning tunneling microscopy (STM) were used for the characterization of prepared systems. The island structure of CeO2 was prepared by the method of reactive evaporation in oxygen atmosphere. The influence of temperature on the electronic structure and morphology was studied. At the temperature above 550 ˚C partial reduction to Ce2O3 and reordering of the islands to the CeO2(331) structure was observed. The ceria promoted oxidation of copper surface was approved, since the clean c(6x2) reconstruction of the surface was observed at the oxygen exposure 1,5 order of magnitude lower then on Cu(110) alone. The other model system was prepared by cerium evaporation to the oxygen precovered Cu(110) surface. The mix of (2x1) and c(6x2) surface reconstruction was formed by oxygen exposition at 300 ˚C. Cerium was deposited on this surface, also at 300 ˚C. During the following heating to 500 ˚C the formation of epitaxial film Ce2O3(0001) was observed, accompanied by the formation of large hundreds nm long smooth band structures in the [11̄0] direction.
|
|
|
Low temperature STM study of metal adsorption on Si(100)2×1
Majer, Karel ; Ošťádal, Ivan (advisor) ; Kocán, Pavel (referee)
The thesis covers the preparation of a UHV system enabling low-temperature measurements by scanning tunneling microscope and the study of one-dimensional aluminium structures on the Si(100)2 × 1 surface. Calibration measurements of deposition rate of Al from an evaporator, temperature of the silicon substrate during annealing and temperature of a cooling device during cooling have been carried out. A STM measurement has been carried out at the temperature of 60řC and aluminium chains on the silicon surface have been observed. Their lengths and forms have been analyzed and length distributions at various tem- perature have been created by using previously obtained data. The observed distributions have been discussed concerning the underlying physical processes. 1
|
|
|
Interaction of metal atoms with metastable reconstructions of the Si(111) surface studied by STM
Matvija, Peter ; Kocán, Pavel (advisor) ; Ošťádal, Ivan (referee)
Process of reconstruction of Si(111) surface after vapor deposition of thallium and subsequent desorption is studied by STM. Dependency of surface coverage on temperature is determined and this dependency is afterwards used for determination of ideal conditions for creation of surface with the biggest possible part with metastable reconstructions (mostly (5x5) and (9x9)). This surface is then covered by vapor deposition by different amounts of Al and possibility of creation of magic clusters and other interesting structures is investigated. Structural models for magic clusters on (5x5) are proposed. The work includes description of experimental devices used in measurements as well as description of procedures and physical principles connected with functioning of STM.
|
|
|
PROBA3 Coronograph System Progress Report
Horodyská, Petra ; Melich, Radek
The scope of this document is to provide to CSL and ESTEC a progress report of ongoing activities as described in Project Management Plan v1_1. TOPTEC main activities cover realization of coronagraph optical elements, housing for this elements, HDD and the Lyot stop realization. In year 2016, the DM model was finished and delivered and the STM model was competely realized and delivered. Toptec started to prepare the documents for Critical Design Review (CDR).
|
|
|
Connecting the TV studios
Flimel, Peter ; Křepelka, Václav (referee) ; Filka, Miloslav (advisor)
In this bachelor thesis work is done TV link study in 2020, for the purpose of mediation football matches between studies in Prague and Bratislava. This work deals with optical connections and technology matters to revel in the transmission of large amounts of data.
|
|
|
Single Atomic Catalysts
Závodný, Adam ; Švec,, Martin (referee) ; Čechal, Jan (advisor)
Single atom catalysts are prospective class of materials, which holds promises to reach the ultimate limit of improvement in catalyst performance, selectivity, lifetime and cost reduction. The ability to efficiently capture the adsorbates at the active sites is the key prerequisite for catalytic transformation to the products. In this respect, our experimental study aims to describe the interaction of gas molecules (H2O, CO, O2 and NO) with single metal atoms (Rh, Ir, Cu) on the magnetite surface employing scanning tunneling microscopy.
|
|
|
Design of Low-Temperature Ultra High Vacuum Scanning Probe Microscopes
Pavera, Michal ; Klapetek, Petr (referee) ; Vetushka, Aliaksei (referee) ; Šikola, Tomáš (advisor)
This thesis deals with the development of scanning probe microscopes. Mechanical requirements for microscopes using measuring methods of scanning tunneling microscopy (STM) and atomic force microscopy (AFM) under enviroments of an ultrahigh vacuum (UHV) and variable temperatures are specified. Mechanical designs of two microscopes are discussed and their control electronics described. A special chapter is devoted to description of linear piezo manipulators and mechanical design of these prototypes.
|
|
|
Design and verification of low temperature part of UHV – STM microscope
Voňka, Jakub ; Rotter, Miloš (referee) ; Urban, Pavel (advisor)
The diploma thesis addresses the design and experimental verification of cooling system and low temperature part of UHV - STM working in temperature range of 20K - 300K. Due to the demand of variable temperature, the flow cooling system with cryogenic (~5 K) helium (He) is used. Two variants of the low temperature part of the microscope are studied. First the version with cooling only the sample holder, and second with cooling of the whole STM. Designed cooling system consists of He flow cryostat allowing to connect it to the Dewar vessel with liquid helium (LHe) using a low-loss transfer line. The cryostat consists of He inlet and outlet, heat exchangers and copper strains (i.e. braids) for the thermal connection of the sample holder/STM and radiation shield around the STM with the heat exchangers. The thesis describes the design of the flow cryostat and its initial tests in the designed vacuum chamber. Heat flow through a spot contact is also discussed to estimate thermal conductance of insulation supports based on thermal resistance of spherical contacts. The thesis was elaborated in collaboration with the Institute of Scientific Instruments of the ASCR, v.v.i.
|
|
|
Development of a linear stage actuator for UHV STM/AFM
Pavelec, Jiří ; Jiruše, Jaroslav (referee) ; Šikola, Tomáš (advisor)
The aim of this diploma thesis is to develop a linear positioning stage for Ultra High Vacuum (UHV) environment. Simple prototypes of the linear positioning stage were designed and incorporated as part of a multiaxis sample manipulator for a UHV Scanning Tunneling Microscopy / Atomic Force Microscopy (STM/AFM). Different types of position encoders and linear guideways are discussed. Implementation of the homodyne interferometer as an optimization tool for a slip-stick based linear stage is described. Scalar diffraction theory is used to model the diffraction grating optical position encoder behavior.
|
|
| |
guest ::
