National Repository of Grey Literature 48 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Histology and micro-CT study of diamond-coated metal bone implants
Potocký, Štěpán ; Ižák, Tibor ; Dragounová, Kateřina ; Kromka, Alexander ; Rezek, Bohuslav ; Mandys, V. ; Bartoš, M. ; Bačáková, Lucie ; Sedmera, David
A conformal coating of a thin diamond layer on three-dimensional metal bone implants was shown directly on stainless steel and TiAl6V4 cortical screw implant using ultrasonic and composite polymer pretreatment method. The best conformation coverage was achieved in the case of the WO3 interlayer for both stainless steel and TiAl6V4 screws. The process of osteointegration of the screw implants into rabbit femurs is evidenced by the formation of a bone edge via desmogenous ossification around the screws in less than six months after implantation. A detailed evaluation of the tissue reaction around the implanted screws shows good biocompatibility of diamond-coated metal bone implants.
Electronic effects at the interface between biomolecules, cells and diamond
Krátká, Marie ; Rezek, Bohuslav (advisor) ; Cifra, Michal (referee) ; Skládal, Petr (referee)
Understanding and control of interactions between biological environment (cells, proteins, tissues, membranes, electrolytes, etc.) and solid-state surfaces is fundamental for biomedical applications such as bio-sensors, bio-electronics, tissue engineering and implant materials as well as for environmental monitoring, security and other fields. Diamond can provide unique combination of semiconducting, chemical, optical, biocompatible and other properties for this purpose. In this thesis we characterize electronic properties of protein-diamond interface by employing a solution-gated field-effect transistor (SGFET) based on hydrogen-terminated diamond, surface of which is exposed to biological media. We elucidate the role of adsorbed protein layer on the electronic response of the diamond transistor. We investigate effects of cells (using mainly osteoblast cells as model) on diamond SGFETs transfer characteristics and gate currents. We employ nanocrystalline diamond (NCD) thin films of different grain sizes (80 - 250 nm) to characterize and discuss influence of grain boundaries and sp2 phase on bio- electronic function of SGFETs. We investigate effects of gamma irradiation on function and stability of hydrogen-terminated diamond SGFETs interfaced with proteins and cells, showing feasibility of...
Fabrication of Graphene and Study of its Physical Properties
Procházka, Pavel ; Rezek, Bohuslav (referee) ; Kalbáč,, Martin (referee) ; Dub, Petr (advisor)
This doctoral thesis is focused on the preparation of graphene layers by Chemical Vapor Deposition (CVD) and their utilization for fabrication and characterization of field effect transistors. The theoretical part of the thesis deals with different methods of graphene production and measurement of its transport properties. In the first part of the experimental section the growth of polycrystalline graphene and individual graphene crystals with sizes up to 300 m is investigated. Further, graphene layer was also grown on an atomically flat copper foils, which were fabricated in order to achieve the growth of graphene of higher quality. Subsequently, the transport properties of field effect transistors produced from the grown layers were measured. The last two chapters deal with a doping of graphene layer by gallium atoms and X-ray radiation. Whereas the deposition of gallium atoms on the graphene surface causes chemical doping of graphene layer by charge transfer, X-ray irradiation of graphene field effect transistors induces the ionization of positively charged defects in dielectrics, which electrostatically dope a graphene layer.
Influence of Si surface passivation on growth and ordering of nanostructures
Matvija, Peter ; Kocán, Pavel (advisor) ; Rezek, Bohuslav (referee) ; de la Torre, Bruno (referee)
Silicon is currently the most widely used semiconductor material with applications ranging from solar cells and sensors to electronic devices. Surface functionalization of silicon with molecular monolayers can be used to tune properties of the material toward a desired application. However, site-specific adsorption of molecules or molecular patterning on silicon surfaces is a difficult task due to the high reactivity of silicon. In this work, we use scanning tunneling microscopy, ab-initio calculations and kinetic Monte Carlo simulations to study adsorption of organic molecules on a bare and thallium-passivated Si(111) surface. We show that the polarity of molecules has a large impact on bonding of the molecules with the bare surface. We demonstrate that, in comparison with the bare surface, molecules or single-atom adsorbates deposited on the Tl-passivated surface have significantly higher mobility. The increased mobility induces formation of 2D gases on the surface and enables formation of self-assembled molecular structures. We propose a novel method to directly visualize the 2D surface gases and we show that a phase of surface gases containing molecule-bound dipoles can be controlled by a non-homogeneous electric field. 1
Back electrode influence on opto-electronic properties of organic photovoltaic blend characterized by Kelvin probe force microscopy
Čermák, Jan ; Miliaieva, Daria ; Hoppe, H. ; Rezek, Bohuslav
Organic photovoltaic (PV) system consisting of P3HT:PCBM blend layer was prepared with an aluminum (Al) back electrode. After the final thermal annealing the Al layer was partially removed. Kelvin Probe Force Microscopy (KPFM) was used to measure photovoltage response to illumination by a solar spectrum light as a function of time (up to 3 weeks). Comparison of the same KPFM measurement on the areas with and without Al revealed differences in both morphology and photovoltage response to illumination. The data are discussed with view to reducing degradation of organic PV devices.\n
Correlated microscopy of electronic and material properties of graphene grown on diamond thin films
Rezek, Bohuslav ; Čermák, Jan ; Varga, Marián ; Tulic, S. ; Skákalová, V. ; Waitz, T. ; Kromka, Alexander
In this work we compare growth of graphene on diamond thin films that enable large area processing. We use films with different crystal size and surface roughness to obtain deeper insight into formation and properties of GoD. The diamond films are coated by a nm thin sputtered Ni layer and heated to 900°C in a forming gas atmosphere (H2/Ar) to initiate catalytic thermal CVD process. The samples are cleaned from residual Ni after the growth process. We employ scanning electron microscopy, Raman micro-spectroscopy and Kelvin probe force microscopy to correlate material, structural, and electronic properties of graphene on diamond. We show how grain size and grain boundaries influence graphene growth and material and electronic properties. For instance we show that the grain boundaries (with non-diamond carbon phases) in diamond films have an important role. They influence the electronic properties and they are beneficial for forming graphene on diamond higher quality.
Spatially separated HOMO/LUMO at interface of polypyrrole physisorbed on oxidized nanodiamond facets
Matunová, Petra ; Jirásek, Vít ; Rezek, Bohuslav
Nanodiamond particles (NDs) have recently risen in popularity owing to their unique and perspective properties. Merging NDs with organic molecules, such as polypyrrole (PPy), into hybrid organic-semiconductor functional systems gives rise to potential applications in photovoltaics (PV), which is supported by prior experimentally observed charge transfer between bulk diamond and PPy. This work focuses on the most relevant (111) and (100) O-terminated ND facets with different coverage of surface terminating oxygens in ether, epoxide, ketone, and peroxide positions. We use density functional theory (DFT) computations employing B3LYP functional and 6-31G(d) basis set. Energetically the most favorable oxidized ND facets were further optimized with PPy in physisorbed configurations. Analysis of geometry, binding energy, HOMO-LUMO gap, and charge transfer was done on the relaxed PPy-ND structures. Multiple hydrogen bonds are formed between PPy amino groups and O atoms on ND surface.
Experimental control of Ce3+ concentration in ceria based model catalysts
Stetsovych, Vitalii ; Mysliveček, Josef (advisor) ; Lykhach, Yaroslava (referee) ; Rezek, Bohuslav (referee)
Concentration of Ce3+ is one of the most important parameters that influence the reactivity of ceria based catalyst. In this work we examine different experimental approaches for controlling Ce3+ concentration in cerium oxide model catalyst systems such as: i) influencing the stoichiometry of ceria, ii) introducing high valence doping agent, and iii) growing ultra thin ceria films with a strong metal substrate interaction. Structure, morphology and chemical state of prepared reduced ceria based systems were examined by means of surface science techniques: scanning tunneling microscopy, low-energy electron diffraction and X-ray photoelectron spectroscopy. In the present work an original method of ceria film reduction was introduced that allows stepwise control on stoichiometry and degree of film reduction (i). Further we introduce preparation procedures for well-ordered tungsten doped ceria model system (ii) and for the high quality 2D ultrathin ceria system on Cu (1 1 1) (iii). Preparation methods and model systems introduced in this work incorporate different physicochemical principles of Ce3+ induction and provide a variety of model systems useful for examining different effects that diversely prepared Ce3+ ions have on the activity of the catalyst.
Structuring and study of electronic and chemical properties of semiconductor surfaces
Verveniotis, Elisseos ; Rezek, Bohuslav (advisor) ; Bartošík, Miroslav (referee) ; Klapetek, Petr (referee)
of thesis Semiconductor materials play a crucial role in modern society as they have become integral parts of our daily life through personal computers, mobile phones, medical implants, solar panels and a plethora of other commercially available electronic devices. The semiconductor industry has been relying predominantly on silicon so far and will continue to do so for a few more years, until the material limits for miniaturization and device engineering are reached. Fortunately, worldwide research has already demonstrated that there are materials exhibiting superior mechanical, electronic, and optical properties and which can thus replace or at least complement silicon. This represents a very important step towards satisfying the ever rising global demand for smaller, faster, energy-efficient and cheaper electronic devices. To that end, nowadays research is focused on fabrication and characterization of diverse materials and nanostructures which are aimed to be integral in electronic devices. Due to the miniaturization, it is essential that the electronic, structural and chemical characterization and modification of those novel materials and structures is performed on the microscopic scale. The relatively young but nevertheless rapidly expanding and exciting field of nanoscience and...

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