A. V. Pavlikov

Synthesis and properties of nanosilicon stabilized by butyl and perfluorobutyl ligands

Nanocrystalline silicon stabilized by butyl and perfluorobutyl ligands that form improper surface states of silicon nanocrystals were synthesized. The presence of perfluorobutyl ligands on the surface of silicon nanocrystals was proved by IR spectroscopy. Nanocrystals with perfluorobutyl ligands form aggregates, which decreases the efficiency of photoluminescence. The nanocrystals with butyl ligands have smaller size but their photoluminescence can be clearly recorded.

Interaction of infrared radiation with free carriers in mesoporous silicon

Features of absorption and reflection of infrared radiation in the range 500–6000 cm−1 are investigated; these features are associated with free carriers in the layers of mesoporous Si (porosity, 60–70%) formed in single-crystal p-Si(100) wafers with a hole concentration of Np≈1020 cm−3. It is found that the contribution of free holes to the optical parameters of the samples decreases as the porosity of the material increases and further falls when the samples are naturally oxidized in air. The experimental results are explained in the context of a model based on the Bruggeman effective medium approximation and the Drude classical theory with a correction for additional carrier scattering in silicon residues (nanocrystals). A comparison between the calculated and experimental dependences yields a hole concentration in nanocrystals of Np≈1019 cm−3 for as-prepared layers and shows a reduction of Np when they are naturally oxidized.

Structural and Optical Properties of Silicon-Carbide Nanowires Produced by the High-Temperature Carbonization of Silicon Nanostructures

Silicon-carbide (SiC) nanowire structures 40–50 nm in diameter are produced by the high-temperature carbonization of porous silicon and silicon nanowires. The SiC nanowires are studied by scanning electron microscopy, X-ray diffraction analysis, Raman spectroscopy, and infrared reflectance spectroscopy. The X-ray structural and Raman data suggest that the cubic 3C-SiC polytype is dominant in the samples under study. The shape of the infrared reflectance spectrum in the region of the reststrahlen band 800–900 cm–1 is indicative of the presence of free charge carriers. The possibility of using SiC nanowires in microelectronic, photonic, and gas-sensing devices is discussed.

Erratum to: “Synthesis and Properties of Nanosilicon Stabilized by Butyl and Perfluorobutyl Ligands”

257 It was found that in the published paper by L.A. Aslanov, V.N. Zakharov, A.V. Pavlikov, S.V. Sa vilov, V.Yu. Timoshenko, and A.V. Yatsenko “Synthe sis and Properties of Nanosilicon Stabilized by Butyl and Perfluorobutyl Ligands” (Russ. J. Coord. Chem., 2013, vol. 39, no. 6, p. 427), the IR spectrum of sili con nanoparticles with perfluorobutyl ligands exhib its absorption bands for dimethoxyethane (solvent), which is removed only partly during drying of silicon nanoparticles obtained in this solvent. The strongest absorption band at 1101 cm–1 proved to be a superpo sition of the strongest solvent band (1110 cm–1) and the Si–O stretching band (1080 cm–1). The positions of 1200 and 1242 cm–1 bands corresponding to the solvent coincided with the positions of the strongest absorption bands of perfluorobutyl ligands. As a result, the band intensities were distorted. The true IR spectrum of silicon nanoparticles with perfluo robutyl ligands will soon be published. Erratum to: “Synthesis and Properties of Nanosilicon Stabilized by Butyl and Perfluorobutyl Ligands” [Russ. J. Coord. Chem., 39, 6 (2013)]

Effect of the initial doping level on changes in the free-carrier concentration in porous silicon during ammonia adsorption

Infrared spectroscopy is used to investigate the effect of ammonia adsorption on the concentration of equilibrium charge carriers in porous-silicon layers with various initial types of dopants at different concentrations. It is found that ammonia adsorption results in an increase in the number of free electrons in n-type samples up to a level exceeding 1018 cm−3. In p-type samples, a nonmonotonic dependence of the charge-carrier concentration on ammonia pressure is observed. The obtained results are accounted for by the appearance of adsorption-induced shallow donor states that, along with the initial-dopant and surface-defect states, specify the charge-carrier type and concentration in the silicon nanocrystals of the porous layer after ammonia adsorption.

Analysis of the Structure and Conductivity of Kinked Carbon Chains Obtained by Pulsed Plasma Deposition on Various Metal Substrates

Linear-chain carbon films with a thickness of order 100 nm were studied by tunneling spectroscopy. The oscillating dependence of the differential conductivity of the investigated structures is established. The results obtained are interpreted using a model of charge-density wave formation in regular structural kinks of carbon chains. The Raman spectra of the films are recorded. The simulated spectra of harmonic oscillations of polyines (–C≡C–)n and cumulenes (=C=)n of carbon films are theoretically compared.

Antireflection Layers for Solar Cells Based on Silicon Nanowires Produced on a Doped Wafer

In this paper, the layers of quantum silicon nanowires produced on highly-doped wafers were studied via the Raman spectroscopy and IR reflection spectroscopy methods. The porosity of layers of different thickness has been determined from IR spectroscopy data using the Bruggeman effective medium model. According to Raman spectroscopy data, the concentration of the free charge carriers in quantum silicon nanowires drops in comparison with that in the wafer. On the basis of these results we conclude that the thickness of a quantum nanowires layer of 2 μm is optimal for its use as an antireflection coating in solar cells. Layers with thicknesses of 10 and 15 μm were studied. It was demonstrated that there is no effect of Raman-scattering enhancement in these layers.

Strength Characteristics of the Filaments and a Basalt Fiber Roving at Different Clamping Lengths and Deformation Rates

The strength properties of filaments and a basalt fiber roving of industrial production were investigated at different clamping lengths and deformation rates. The deformation rate for filaments was varied from 1 to 20 mm/min, but the clamping lengths selected were 10, 20, 30, and 50 mm. No clamping-length-dependence of strength parameters of the roving in the range of 350-600 mm was detected. The results found for basalt fiber filaments were compared with published data for Kevlar29 aramid, T300 carbon, and Advantex glass fiber filaments.

Analysis of the Raman Spectrum of Kinked Carbon Chains Taking into Account the Model of Various End Groups

The Raman spectra of kinked carbon chains with a set of end groups composed of hydrogen, silver, and copper atoms are calculated. It is analyzed how end groups, as well as the positions of impurity atoms in the chain, affect shifts characterizing the main peaks of the harmonic vibrations of chemical bonds between carbon atoms in polyyne- and cumulene-like (respectively, (–C≡C–)n and (=C=)n) chains.

Increasing the Strength of Single Filaments and Yarns of a Paraaramid Fiber by Their Processing with an Aqueous Suspension of Carbon Nanoparticles

The paper presents the results of increasing the strength and modulus of single filaments and yarns of a paraaramid fiber by their processing with an aqueous suspension of carbon nanotubes in the production process