National Repository of Grey Literature 38 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
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.
STM study of adsorption of metals on the Si(111) 7x7 surface
Setvín, Martin ; Ošťádal, Ivan (advisor) ; Nehasil, Václav (referee)
The work is focused on studying of a single silver adatom hopping inside a half unit cell of Si(111)-7×7 reconstruction. It is possible to estimate activation energies and frequency prefactors for hops between particular adsorption sites. It was necessary to make fundamental modifications on a low temperature STM as a part of the work. The modificaations have been made on top of a sample cooling system and on inertial motor for coarse approach of the sample to a tip. The vacuum properties of the STM chamber have been improved. A considerable progress in technology of electrochemically etched tungsten tip preparation has been achieved. Further treatement of the tips has been studied with accent on field emission effect on the tip apex. The 7×7 reconstruction could not be prepared inside the vacuum chamber. Reason is probably a poor degassing of the sample. Further planned experiments could not be performed so far. This thesis contains detailed theoretical analysis of the studying of adsorption sites. The tests of time dependent tunelling spectroscopy method are described in results.
STM study of growing 1D nanostructures composed by III and IV group atoms
Kučera, Michael ; Ošťádal, Ivan (advisor) ; Mysliveček, Josef (referee)
In the presented work we study Al and Sn on a Si(100)2$\times$1 surface by means of STM. Peculiarities of displaying and morphology of metallic structures are investigated. Utilizing the STM to investigate Al and Sn, we obtain the growth characteristics for various coverage and temperatures at deposition. It is shown, that island size distribution is scalable for both metals and has a qualitatively different character. In order to interpret the growth characteristics and obtain unknown microscopic parameters, a new software tool for kinetic Monte Carlo (kMC) simulations of aluminum was conceived.
Solved Problems in Physics for Electronic Collection - Magnetic field
Popová, Markéta ; Koupilová, Zdeňka (advisor) ; Ošťádal, Ivan (referee)
The main focus of this diploma thesis was to create structured tasks from topical unit Magnetic field. They are published in the electronic collection of solved exercises in physics now and they complement the tasks created in previous bachelor's thesis. Each task contains hints, analysis, detailed solution, computation, and is complemented with ilustratived pictures. The structured solutions are aimed at helping the reader with self-study and lead him to thinking about given problems. In the scope of this diploma thesis, were created more complicated tasks for grammar school level that can be used as teacher's preparation for an interesting lesson or seminar, and tasks at the university level of difficulty. The next task was to analyze the topic "magnetic field" from the point of view of elementary school, grammar school and first grade of university, and, on the basis of the term analysis, put the created tasks into the structure of given topical unit and eventually suggest their appropriate use in the education process.
STM study of metal adatom mobility on Si(100) surface
Rozbořil, Filip ; Ošťádal, Ivan (advisor) ; Mysliveček, Josef (referee)
Surface diffusion of group III and IV metals on Si(100) is studied. Three methods for obtaining diffusion barriers are presented and discrepancies in published results are discussed. Room temperature growth of Al on Si(100) is studied using STM, observing a monomodal scaled island size distribution function. A Kinetic Monte Carlo simulation model is employed to obtain bonding energies and diffusion barriers for Al/Si(100). The best agreement between the measured and simulated characteristics is found for strongly anisotropic diffusion with barriers 0.60 eV in the direction orthogonal to the Si dimer rows and 0.80 eV in the parallel direction. Modifications of the cooling system required for observing metal adatom diffusion on Si(100) using STM are described and the first low-temperature experiment is carried out.
Adsorption and mobility of Al adatoms on Si(100) surface
Majer, Karel ; Ošťádal, Ivan (advisor) ; Mysliveček, Josef (referee)
The subject of the thesis is growth of aluminium structures one-dimensional chains on Si(100) surface. Growth characteristics of Al on Si(100) at room temperature and at higher temperature and various coverages were measured using STM. The results are discussed with respect to previous experiments and a way to find the value of activation energy of surface migration is proposed. An important part of the thesis is preparation and tests of a new low-temperature UHV apparatus for STM experiments. Functions of the apparatus are described. A way to prepare clean Si(100) surface as well as the methods of achieving atomic-scale resolution in STM were found in conditions previously unknown. A test of evaporators for Al and Sn is described. Al deposition has not been successful in the new apparatus yet. Sn deposition has been successful and low-temperature structures of tin on Si(100) were observed. They differ from room-temperature structures and contain kinks which were previously observed only in Al structures.
STM study of adsorption and mobility of phtalocyanine molecules on passivated silicon surfaces at lower temperatures
Szabo, Michal ; Ošťádal, Ivan (advisor) ; Matvija, Peter (referee)
The thesis deals with an experiment for studying adsorption of phthalocyanin molecules on silicon surface passivated by a tin reconstruction. The main technique used for imaging surface is scanning tunneling microscopy (STM). The work contains a brief introduction to the studied problem. It deals with the STM method and STM construction. The used ultra-vacuum experimental system is characterized together with particular steps at sample preparation for STM measurements. During the sample preparation all necessary operations were tested on the newly modified system and calibration measurements of sample annealing and tin deposition were performed. A structure of the prepared surface Si(111) 7×7 was investigated by STM and conditions for the preparation in the new system were specified. STM images were used for an evaluation of results at optimizing preparation of the passivated surface. Obtained results are important for further experiments in frame of a research focused on growing molecular structures on silicon surfaces.

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