A. G. Kurenya

Synthesis and structure of films consisting of carbon nanotubes oriented normally to the substrate

Films consisting of oriented carbon nanotubes (CNTs) are synthesized by thermal decomposition of a carboniferous compound + ferrocene mixture and studied by scanning electron microscopy. It is shown that the thickness and structure of the films depend on the synthesis conditions, specifically, on the way the reaction mixture is introduced. Multiple injection of the reaction mixture causes growth of multilayer CNT films, the number of layers in which equals the number of injections. The basic possibility of CNT continuous growth normally to the substrate surface is demonstrated. A mechanism behind the layered structure of the films consisting of oriented CNTs is suggested.

Effect of oxidative treatment on the electrochemical properties of aligned multi-walled carbon nanotubes

Vertically aligned multi-walled carbon nanotubes (MWNTs) were grown on the surface of electroconductive silicon substrate by catalytic chemical vapor deposition (CCVD) of a mixture of toluene and ferrocene vapors at 800°С. The anisotropic structure of the array that is due to the mutual orientation of MWNTs makes such materials attractive for use as supercapacitor electrodes. The effect of iron nanoparticles encapsulated in MWNTs as a result of synthesis on the electrochemical capacity of the sample in a 1 М H2SO4 solution was studied. Iron was removed during the thermal treatment of the MWNT array in a 20% H2SO4 solution under the normal or hydrothermal conditions. The contribution of redox processes involving iron was shown to be comparable to the contribution of the double-layer capacity of MWNTs. The hydrothermal treatment allows easy separation of the array from the silicon substrate without any loss of electric coupling of MWNTs.

The field emission properties of carbon nanotubes and SiC whiskers synthesized over Ni particles deposited in ion tracks in SiO2

Carbon nanotubes (CNTs) and SiC whiskers are synthesized by the pyrolysis of acetonitrile vapor over Ni nanoparticles deposited in the pores obtained by etching heavy ion tracks in dielectric SiO2 layers on single crystal silicon substrates. The structures obtained are studied by scanning electron microscopy and Raman spectroscopy, and their field emission characteristics are measured. The formation of CNTs or SiC whiskers as a result of catalytic hydrocarbon pyrolysis is found to depend on the occupation of ion tracks by nickel clusters. It is shown that the threshold of electron emission appearance is 1 V/µm for both types of the samples and that differences in the shape of current-voltage characteristics are explained by differences in the electronic structure of CNTs and SiC whiskers.

A Laboratory CVD Reactor for the Synthesis of Vertically Oriented Carbon Nanotube Arrays

The functional structure and the design of a CVD reactor for the synthesis of vertically oriented carbon nanotube (VOCNT) arrays on silicon substrates are described. To synthesize VOCNTs, various organic compounds, viz., toluene, cyclohexane, and acetonitrile, and their mixtures in the liquid state were tested under normal conditions.

The Automation of a CVD-Reactor for the Synthesis of Vertically Oriented Carbon Nanotube Arrays

The functional diagram and the automation system of a CVD-reactor for the synthesis of vertically oriented carbon nanotube arrays on silicon substrates are described. The system is intended predominantly for recording the physical parameters of the CVD-reactor in real time, generating the instructions for the operator on the selected synthesis-process flow, on-screen display of the selected parameters, and management of the automatic protection of the reactor units and assemblies against contingencies or unspecified actions of the operator. The structure of the system for data acquisition, visualization of synthesis variables, and the CVD process control that allows the synthesis of vertically oriented carbon nanotube arrays is presented.

An X-ray spectroscopy study of CdS nanoparticles formed by the Langmuir–Blodgett technique on the surface of carbon nanotube arrays

The composition and electronic structure of cadmium sulfide (CdS) nanoparticles formed by the Langmuir–Blodgett (LB) technique on clean silicon wafers and the surface of vertically aligned carbon nanotube (CNT) arrays are studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The samples were annealed in a vacuum at 175 °C and 225 °C to remove the organic matrix of the LB film. From the analysis of the XPS data the increased concentration of sulfate groups on the surface of CdS nanoparticles formed on CNTs and the electron density transfer from CdS to CNTs are determined. An increase in the LB film annealing temperature causes an increase in the degree of crystallinity and the CdS crystallite size and a decrease in the photoluminescence intensity of a CdS–CNT hybrid.

Effect of iron nanoparticles in the films of composite materials and carbon nanotubes on the angular dependence of X-ray emission

The angular dependences of X-ray emission were measured for a series of polymer film samples with different concentration of finely dispersed iron. X-ray fluorescence maximum was found to shift toward higher angles with increasing the iron concentration in a sample. The form of angular dependences of X-ray emission was calculated taking into account the particle absorption coefficients in a composite material for incident and emitted radiation. The experimental and theoretical dependences were compared to estimate the content of nanoparticles in the polymer composite and iron nanoparticles in the samples of oriented carbon nanotubes.

THERMAL CVD SYNTHESIS OF CARBON NANOTUBES IN SWIFT HEAVY ION TRACKS OF SILICON DIOXIDE

During the last years, a growing interest in the creation of micro- and nanoelectronic devices by use of the swift heavy ion track technology in a combination with carbon nanotubes (CNTs) is observed in several research centers worldwide. The CNTs were grown in etched ion tracks in SiO2 layers on Si. For this purpose, Ni-catalyst nanoclusters were electrochemically deposited within the ion tracks. The geometry of the obtained nanostructures has been analyzed. Structure features of CNTs obtained by thermal chemical vapor deposition have been investigated.