Magdaléna Kadlečíková

Atmospheric pressure microwave torch for synthesis of carbon nanotubes

The microwave (mw) plasma torch at atmospheric pressure has been studied for carbon nanotube (CNT) synthesis. The depositions were carried out on silicon substrates with 515 nm thin iron catalytic overlayers from the mixture of argon, hydrogen and methane. The optical emission spectroscopy of the torch showed the presence of C2 and CH radicals as well as carbon and hydrogen excited atoms. The vicinity of the substrate influenced the relative intensities and increased the emission of C2. For fixed mw power, the temperature of the substrate strongly depended on its position with respect to the nozzle electrode and on the gas mixture, particularly the amount of H2. The speed of the substrate heating during an early deposition phase had a significant effect on the CNT synthesis. An abrupt increase of the temperature at the beginning increased the efficiency of theCNTsynthesis. Areas of dense straight standing CNTs, 30 nm in average diameter, with approximately the same sized iron nanoparticles on their tops were found in accordance with the model of growth by plasma enhanced chemical vapour deposition. However, the deposit was not uniform and a place with only several nanometres thick CNTs grown on much larger iron particles was also found. Here, taking into account the gas temperature in the torch, 31003900 K, we can see similarities with the dissolutionprecipitation model of the CNT growth by high temperature methods, arc or laser ablation.

Physical Properties of Fluoride Glasses for Ionics

The ionic conductivity and permittivity of glasses based on ZrF4, BaF2, LaF3, AlF3 and NaF (ZBLAN) or PbF2, InF3, BaF2, AlF3 and LaF3 (PIBAL) are studied. The influence of the glass composition on the glass transition temperature (Tg) and on the crystallization temperature (Tx) is reported. For all ZBLAN glasses the temperature dependencies of the ionic conductivity are close one to another (s500 = 8(2)·10-6 S/cm) and their conduction activation enthalpies are equal to 0.82(1)eV. From the point of view of the ionic conductivity, the best glass compositions are the PIBAL50 (50 m/o PbF2) and PIB45 ( 45 m/o PbF2).

Diamond icosahedron on a TiN-coated steel substrate

Diamond layers have been deposited by hot filament chemical vapour deposition (HF CVD) on TiN-coated steel substrates. After deposition, we could observe separate, well-developed diamond icosahedrons and decahedrons on the surface. We have found that a lower content of methane in hydrogen supports their growth, this being a result of multifold twinning. The quality of diamond layers has been evaluated by Raman spectroscopy and scanning electron microscopy.

Indication of Intrinsic Macroscopic Forces Affecting Magnetic Properties of Fe-Nb/Mo-Cu-B-Si Ribbons

Si-rich (at.% Si >; 12) Fe-Nb/Mo-Cu-B-Si nanocrystalline ribbons are already successfully used in industry. Still the impact of intrinsic macroscopic stresses on magnetic anisotropy is not known in enough detail. Domain structure, hysteresis loops and surface chemistry have been studied in the as-annealed (nanocrystalline) state as well as the response to surface removal by etching. Creep-induced anisotropy established during annealing was found to be the essential source of the observed anisotropy. Apparently smooth gradient of transversal to longitudinal creep-induced anisotropy was identified from air-side center across the ribbon width as well as across the ribbon thickness. The relative rise of transversal anisotropy due to surface removal points to different surface etching efficiency. Raman spectroscopy confirmed the presence of ferrous oxides on both the ribbon surfaces. The existence of a defined oxide layer generating the macroscopic stress was not indicated.

Raman bands in microwave plasma assisted chemical vapour deposited films

Raman spectroscopy is employed to characterize thin diamond films deposited by microwave plasma assisted chemical vapour deposition technique using a gas mixture of methane and hydrogen. The surface morfology of the films was analyzed by scanning electron microscopy. We have identified submicron crystals on (100) facets of diamond crystals which gave rise to bands in the Raman spectrum centred at 1170 and 1456 cm-1.

Differentiation of selected blue writing inks by surface-enhanced Raman spectroscopy

Raman spectroscopy and surface enhanced Raman spectroscopy were used to examine 14 blue inks obtained from commercially available stationery. Standard colouring agents in the inks: β-phase of phtalocyanine blue PB15 and some homologues of the methyl violet class, were identified. Surface enhanced Raman spectra were recorded on a firm heterostructure of silver/nanocrystalline diamond/silicon constituting an active substrate providing the possibility to write directly on the surface. Based on the differences in traditional and surface enhanced Raman spectra, two inks were identified unambiguously, the remaining inks were categorised into three groups exhibiting common spectral features. Despite their similarity, surface enhanced Raman spectra exhibited soft variations enabling discrimination of the inks, thus proving the usefulness of the method.

Raman Spectra of Two Samples of Rubrene Layers

Raman Spectra of Two Samples of Rubrene Layers This experimental work deals with measuring Raman spectra of rubrene. The objective is to optimize the measurement procedure of rubrene layers on a substrate. The main outcome of the work is identification of rubrene and of the single-crystalline nature of the measured spots of the rubrene layer.

Study of Carbon Films on Silicon Substrates

Carbon based films on silicon substrates have been studied by high resolution FE SEM equipped by an EDS analyzer. The first type are carbon nanotube (CNT) [1] films prepared on Si/SiO2 substrates with Ni or Fe layers by radiofrequency plasma chemical vapor deposition. Dependence of nanotube films properties on Ni and Fe thickness and deposition conditions have been studied. The second type of films discussed are microcrystalline and nanocrystalline diamond films grown on pre-treated Si substrates by microwave plasma chemical vapor deposition (MPCVD). The pre-treatment was varied and its effect on diamond films was studied.

General Comment on Particle Size Analysis

This article summarizes the main topics related to the issue of particle size analysis. It provides a discussion of the term ’particle’ and briefly describes the advantages and disadvantages of the most important particle size analysis methods.

The principle of a new thermometer in HF CVD reactor

The topic of the submitted article is the issue of measuring the temperature in a hot filament chemical vapour deposition (HF CVD) reactor by a purpose-built electronic circuit. The topical objective is to optimize the substrate temperature, one of the key technological parameters in the synthesis of carbon nanotubes. Design and construction of a functional thermometer and its calibration and, hereby, improved accuracy of temperature measurement is the main outcome of this experimental work.