Yu. A. Ivanova

On the morphology of Si/SiO 2 /Ni nanostructures with swift heavy ion tracks in silicon oxide

Si/SiO2/Ni nanostructures are fabricated by the irradiation of an oxidized Si surface with swift heavy ions, nanopore etching in the SiO2 layer, and the electrochemical deposition of nickel in the nanopores with their partial (∼50%) or complete filling. Studies of the morphology of the metal in the nanopores shows that the nickel-cluster structure is rather homogeneous and formed by crystallites ∼30–50 nm in size. The effects of deposition modes and structure morphology on current transport are analyzed with the use of test temperature dependences of the magnetoresistance. The reproducibility and stability of the magnetoresistance values for the case of homogeneous structure and pore filling with nickel make the Si/SiO2/Ni system promising for application as the base element for high-sensitivity low-temperature magnetic field sensors.

Photoelectrochemical processes on TiO2 electrodes sensitized by lead selenide nanoparticles

The effect of spectral sensitization of photoelectrochemical processes on the surfaces of mesoporous TiO2 modified by electrochemically deposited PbSe nanoparticles has been observed.

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.

Enhanced magnetoresistive effect in the arrays of nickel nanorods on silicon substrates

It is shown that the magnetoresistive properties of n–Si/SiO2/Ni, nanostructures containing nanogranular nickel rods in a SiO2 layer’s vertical pores substantially differ from the similar properties in the earlier studied nanogranular Ni films electrodeposited onto the n–Si plates. From the point of view of the electrophysical properties, the nanostructures studied are analogous to a system of two Schottky Si/Ni diodes, which are connected to each other. The magnetoresistance of such structures has been studied in the temperature range from 2 to 300 K and the magnetic field range of up to 8 Tl. It is established that at temperatures of 17–27 K the structures possess a positive magnetoresistive effect, whose value depends on the transverse voltage applied to the structure and increases with a decrease in the longitudinal (along the rods) current intensity. At a current of 100 nA, the relative magnetoresistance in the field of 8 Tl increases from 500 to 35000% by an increase in the transverse voltage from 0 to–2 V. The observed magnetoresistive effect is associated with the influence of the magnetic field on the processes of impact ionization of impurities resulting in an avalanche breakdown of the Ni/Si Schottky barrier. Thus, the possibility of controlling the magnetoresistive effect in n–Si/SiO2/Ni template structures by applying an additional (transverse) electric field to the nanostructure between the silicon substrate (as the third electrode) and nickel rods is proven.

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.