E.V. Knyazev

An observation of the radial breathing mode in the Raman spectra of CVD-grown multi-wall carbon nanotubes

Abstract MWCNTs grown by chemical vapor deposition on SiO 2 /Si substrates were investigated by Raman spectroscopy, transmission electron microscopy (TEM), Auger spectroscopy, and X-ray photoelectron spectroscopy before and after an annealing at 390 °C for 120 min in air or chemical treatment with a HCl solution. The Raman spectroscopy was focused on the low-frequency (250-300 cm −1 ) band. It is found that the positions and full widths at half maximum of the peaks forming the 250-300 cm −1 Raman band change little with the annealing or chemical treatment. The measured inner diameters of small-diameter CNTs from TEM agree well with those from Raman spectroscopy. These indicate that the low-frequency band originates from the radial breathing oscillations of carbon atoms in the inner walls of small-diameter MWCNTs.

Features of the effect of a high-power ion beam on polymer films deposited onto dielectric substrates

The effect of a nanosecond high-power ion beam on chlorinated polyvinyl chloride, reactive polymer with a conjugation system (poly-vinylene chloride), and FP-383 photoresist thin films, which are deposited onto sodium-silicate glass and ST-50 glass-ceramic substrates, is investigated. It is revealed that submicrometer particles with clearly defined crystallographic facets are formed on the irradiated surface of the chlorinated polymers. These particles include predominantly carbon and are probably carbynoid or diamond-like structures. The possible mechanisms of the observed phenomena are discussed.

AES and XPS studies of a por-Si/SnOx nanocomposite formed using a powerful ion beam of nanosecond duration

The results of the X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM) investigations of tin-oxide nanolayers on samples of por-Si/SnOx composites with varying matrix porosity, formed using a powerful ion beam of nanosecond duration, are presented. It is shown that rapid melting and crystallization of the surface leads to the formation of Si nanoparticles with a maximal size of 200 nm. It is established that tin is included in the structure of the nanocomposite in an oxidized state with a small inclusion of metallic β tin. With increasing porosity, the phase composition of the tin nanolayers becomes closer to the state corresponding to the highest tin oxide (SnO2). It is also shown that, upon an increase in the porosity, the intensity of the tin 4d subvalent line increases, which is, apparently, associated with an enhanced degree of hybridization of tin and oxygen atoms. The changes in the elemental composition of the composite and the depth of tin penetration are estimated from the results of ion etching.

Formation and properties of the buried isolating silicon-dioxide layer in double-layer “porous silicon-on-insulator” structures

The oxidation of mesoporous silicon in a double-layer “macroporous silicon–mesoporous silicon” structure is studied. The morphology and dielectric properties of the buried insulating layer are investigated using electron microscopy, ellipsometry, and electrical measurements. Specific defects (so-called spikes) are revealed between the oxidized macropore walls in macroporous silicon and the oxidation crossing fronts in mesoporous silicon. It is found that, at an initial porosity of mesoporous silicon of 60%, three-stage thermal oxidation leads to the formation of buried silicon-dioxide layers with an electric-field breakdown strength of Ebr ~ 104–105 V/cm. Multilayered “porous silicon-on-insulator” structures are shown to be promising for integrated chemical micro- and nanosensors.

Changes in the chemical state and concentration of iron in carbon nanotubes obtained by the CVD method and exposed to pulsed ion irradiation

Data on the distribution of iron in nitrogen-containing multiwall carbon nanotubes (N-MWCNTs) and changes in its chemical state and concentration under different parameters of irradiation by a pulsed ion beam are obtained by methods of transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersion analysis. It is shown that the irradiation of N-MWCNTs with an energy density of 0.5 J/cm2 lead to the formation, on their lateral surfaces, of structures with a size of 2–10 nm, consisting of metallic iron encapsulated in a carbon shell. An increase in the energy density to 1–1.5 J/cm2 leads to a substantial removal of iron clusters from the tips of carbon nanotubes and a reduction in the amount of iron in the bulk of the N-MWCNT layer.

Study of multilayer carbon nanotubes subjected to the impact of a nanosecond high-energy ion beam

The impact of a nanosecond high-energy ion beam on the structure and morphology of multilayer carbon nanotubes and their ensembles is studied using transmission electron microscopy and scanning electron microscopy. It is shown that ion-beam irradiation leads to a decrease in the outer diameters of carbon nanotubes, which is related to the destruction of their outer layers. In addition, the secondary growth of carbon nanotubes with smaller diameters and the growth of bulblike formations, inside which structures with interplanar distances that are close to those of nanodiamond are fixed, are observed.

Synthesis of nanocomposite CNT/SnO x for Gas microsensors

Nanocomposites on the basis of CNT layers and nonstoichiometric tin dioxide (CNT/SnO<inf>x</inf>) have been obtained. Gas sensitivity to ethanol (C<inf>2</inf>H<inf>5</inf>OH) and nitrogen dioxide (NO<inf>2</inf>) vapor at the room temperature has been established.