Stanislav Haviar

Preparation of Magnetron Sputtered Thin Cerium Oxide Films with a Large Surface on Silicon Substrates Using Carbonaceous Interlayers

The study focuses on preparation of thin cerium oxide films with a porous structure prepared by rf magnetron sputtering on a silicon wafer substrate using amorphous carbon (a-C) and nitrogenated amorphous carbon films (CNx) as an interlayer. We show that the structure and morphology of the deposited layers depend on the oxygen concentration in working gas used for cerium oxide deposition. Considerable erosion of the carbonaceous interlayer accompanied by the formation of highly porous carbon/cerium oxide bilayer systems is reported. Etching of the carbon interlayer with oxygen species occurring simultaneously with cerium oxide film growth is considered to be the driving force for this effect resulting in the formation of nanostructured cerium oxide films with large surface. In this regard, results of oxygen plasma treatment of a-C and CNx films are presented. Gradual material erosion with increasing duration of plasma impact accompanied by modification of the surface roughness is reported for both types of films. The CNx films were found to be much less resistant to oxygen etching than the a-C film.

Thickness dependent wetting properties and surface free energy of HfO2 thin films

We show here that intrinsic hydrophobicity of HfO2 thin films can be easily tuned by the variation of film thickness. We used the reactive high-power impulse magnetron sputtering for preparation of high-quality HfO2 films with smooth topography and well-controlled thickness. Results show a strong dependence of wetting properties on the thickness of the film in the range of 50–250 nm due to the dominance of the electrostatic Lifshitz-van der Waals component of the surface free energy. We have found the water droplet contact angle ranging from ≈120° for the thickness of 50 nm to ≈100° for the thickness of 2300 nm. At the same time the surface free energy grows from ≈25 mJ/m2 for the thickness of 50 nm to ≈33 mJ/m2 for the thickness of 2300 nm. We propose two explanations for the observed thickness dependence of the wetting properties: influence of the non-dominant texture and/or non-monotonic size dependence of the particle surface energy.

Evolution of microstructure and macrostress in sputtered hard Ti(Al,V)N films with increasing energy delivered during their growth by bombarding ions

This letter reports on the effect of the energy Ebi, delivered to the sputtered Ti(Al,V)N film by bombarding ions, on its microstructure, macrostress σ, mechanical properties, and resistance to cracking. The films were deposited by reactive magnetron sputtering. Interrelationships between these parameters were investigated in detail. It was shown that (1) the increase of the energy Ebi makes it possible to convert (1) the film microstructure from columnar to dense, noncolumnar, (2) the macrostress σ from tensile (σ > 0) to compressive (σ < 0), (3) the brittle hard film with low ratio H/E* < 0.1 and low elastic recovery We < 60% to the flexible hard film with high ratio H/E* ≥ 0.1 and high elastic recovery We ≥ 60%, (2) the flexible hard Ti(Al,V)N films with high ratio H/E* ≥ 0.1, high elastic recovery We ≥ 60%, and compressive macrostress can be formed not only in the transition zone (zone T in which the films exhibit a dense, voids-free microstructure) of the Thorntons structural zone model (SZM) but al...

Porcine liver vascular bed in Biodur E20 corrosion casts

BACKGROUND Pigs are frequently used as animal models in experimental medicine. To identify processes of vascular development or regression, vascular elements must be recognised and quantified in a three-dimensional (3D) arrangement. Vascular corrosion casts enable the creation of 3D replicas of vascular trees. The aim of our study was to identify suitable casting media and optimise the protocol for porcine liver vascular corrosion casting. MATERIALS AND METHODS Mercox II® (Ladd Research, Williston, Vermont, USA) and Biodur E20® Plus (Biodur Products, Heidelberg, Germany) were tested in 4 porcine livers. The resins (volume approximately 700 mL) were injected via the portal vein. Corrosion casts were examined by macro-computed tomography, micro-computed tomography and scanning electron microscopy. RESULTS For hepatectomies, the operating protocol was optimised to avoid gas or blood clot embolisation. We present a protocol for porcine liver vascular bed casting based on corrosion specimens prepared using Biodur E20® epoxy resin. CONCLUSIONS Only Biodur E20®Plus appeared to be suitable for high-volume vascular corrosion casting due to its optimal permeability, sufficient processing time and minimum fragility. Biodur E20® Plus is slightly elastic, radio-opaque and alcohol-resistant. These properties make this acrylic resin suitable for not only vascular research but also teaching purposes.

E–beam lithography processing of Au–nanowire contacts for development of gas sensors based on tungsten–oxide nanorods self–assembled on mica

This work describes the processing of Au nanowire arrays on insulating substrate developed to contact tungsten–oxide nanorods self–organised on the mica surface. The combination of electron beam lithography in scanning electron microscope and lift–off process is shown to be effective in fabricating nanocontact finger patterns with a line width of about 270 nm and 400 nm on bare and WO3 nanorod covered mica surfaces, respectively, separated by a few micrometre distance. It is shown that at right selection of the distance between Au nanowires, the applied procedure makes possible to contact WO3 nanorods of different length and density even if the nanostructures do not form an interconnected net. It opens the way for fabrication of single–wire nanosensors grown on insulating substrates.

The use of porcine corrosion casts for teaching human anatomy

In teaching and learning human anatomy, anatomical autopsy and prosected specimens have always been indispensable. However, alternative methods must often be used to demonstrate particularly delicate structures. Corrosion casting of porcine organs with Biodur E20® Plus is valuable for teaching and learning both gross anatomy and, uniquely, the micromorphology of cardiovascular, respiratory, digestive, and urogenital systems. Assessments of casts with a stereomicroscope and/or scanning electron microscope as well as highlighting cast structures using color coding help students to better understand how the structures that they have observed as two-dimensional images actually exist in three dimensions, and students found using the casts to be highly effective in their learning. Reconstructions of cast hollow structures from (micro-)computed tomography scans and videos facilitate detailed analyses of branching patterns and spatial arrangements in cast structures, aid in the understanding of clinically relevant structures and provide innovative visual aids. The casting protocol and teaching manual we offer can be adjusted to different technical capabilities and might also be found useful for veterinary or other biological science classes.

Hard TiN2 dinitride films prepared by magnetron sputtering

This letter reports on the formation of hard TiN2 dinitride films prepared by magnetron sputtering. TiN2 films were reactively sputtered in an Ar + N2 gas mixture using a pulsed dual magnetron with a closed magnetic field B. The principle of the formation of TiN2 films by magnetron sputtering is briefly described. The stoichiometry x = N/Ti of the TiNx films was controlled by deposition parameters, and its maximum value of x = 2.3 was achieved. For the first time, a possibility to form the TiN2 dinitride films by magnetron sputtering has been demonstrated. The mechanical properties of sputtered films were investigated in detail.This letter reports on the formation of hard TiN2 dinitride films prepared by magnetron sputtering. TiN2 films were reactively sputtered in an Ar + N2 gas mixture using a pulsed dual magnetron with a closed magnetic field B. The principle of the formation of TiN2 films by magnetron sputtering is briefly described. The stoichiometry x = N/Ti of the TiNx films was controlled by deposition parameters, and its maximum value of x = 2.3 was achieved. For the first time, a possibility to form the TiN2 dinitride films by magnetron sputtering has been demonstrated. The mechanical properties of sputtered films were investigated in detail.