Mikhail Yu. Vasilkov

Spectral optical properties of synthesized ceramic nanoporous membranes based on anodic aluminum oxide coated silver in saturated ammonia gas flow have been experimentally investigated. Based on the measured transmission spectra and detected interference part of the spectra in wavelength range from 550 to 900 nm, temporal and spectral dependencies of the effective optical thickness and its changes in non-equilibrium conditions were obtained due to adsorption of ammonia molecules on silver film surface. According to detected and measured interference maximum shifts up to 14 nm in transmission spectra of Al₂O₃ + Ag membranes in ammonia gas flow, the possibility of constructing a selective interferometric optical sensors with 10–15 min response time is shown.

The results of experimental studies of ohmic conductivity degradation in the ensembles of nanostructured anatase bridges under long-term effect of direct current are presented. Stochastic sets of interelectrode partially conducting bridges consisting of close-packed anatase nanoparticles were formed by the seeding particles from drying aqueous suspensions on the surfaces of silica substrates with interdigital platinum electrodes. Multiple-run experiments at room temperature have shown that ohmic conductivity degradation in these systems is irreversible. It is presumably due to accumulated capture of conduction electrons by deep traps in anatase nanoparticles. The scaling analysis of voltage drops across the samples at the final stage of degradation gives a critical exponent for ohmic conductivity as 1.597. This value satisfactorily agrees with the reported model data for percolation systems. At an early stage of degradation, the spectral density of conduction current fluctuations wihin the frequency range of 0.01 Hz - 1 Hz decreases approximately as , while near the percolation threshold the decrease trend changes to . This transition is interpreted in terms of an increasing contribution of blockages and subsequent avalanche-like breakdowns of part of the local conduction channels in the bridges into electron transport near the percolation threshold.

A method is presented for obtaining thin-film mesoporous coatings for protective glasses in nano- and optoelectronic devices for various purposes, including: obtaining titanium oxide sols with the addition of silver nitrate, applying coatings by the “dipcoating” method with further heat treatment. The kinetic constants of Smoluchowski's fast and slow coagulation and the activation energy of the process at various concentrations of silver nitrate were calculated. The optimal concentration of silver nanoparticles in the ash was determined by the least squares method.

The results of experimental studies of the effect of degradation of macroscopic charge transport in ensembles of close-packed anatase nanoparticles under long-term action of a constant electric field are presented. The degradation is presumably due to the increasing degree of blocking of statistically independent conduction channels formed in ensembles of particles under the field action. A phenomenological model is considered for estimating the number of active conduction channels in an ensemble of particles near the percolation threshold in the system. Keywords: nanoparticles, anatase, charge transfer, percolation threshold.

The results of experimental studies of the effect of degradation of macroscopic charge transport in ensembles of close-packed anatase nanoparticles under long-term action of a constant electric field are presented. The degradation is presumably due to the increasing degree of blocking of statistically independent conduction channels formed in ensembles of particles under the field action. A phenomenological model is considered for estimating the number of active conduction channels in an ensemble of particles near the percolation threshold in the system.

Spectral optical properties of synthesized ceramic nanoporous membranes based on anodic aluminum oxide coated silver in saturated ammonia gas flow have been experimentally investigated. Based on the measured transmission spectra and detected interference part of the spectra in wavelength range from 550 to 900 nm, temporal and spectral dependencies of the effective optical thickness and its changes in non-equilibrium conditions were obtained due to adsorption of ammonia molecules on silver film surface. According to detected and measured interference maximum shifts up to 14 nm in transmission spectra of Al₂O₃ + Ag membranes in ammonia gas flow, the possibility of constructing a selective interferometric optical sensors with 10-15 min response time is shown. Keywords: porous anodic aluminium oxide, membrane, silver film, light interference, ammonia vapors, effective optical thickness, interference maximum shift.

Spectral optical properties of synthesized ceramic nanoporous membranes based on anodic aluminum oxide coated silver in saturated ammonia gas flow have been experimentally investigated. Based on the measured transmission spectra and detected interference part of the spectra in wavelength range from 550 to 900 nm, temporal and spectral dependencies of the effective optical thickness and its changes in non-equilibrium conditions were obtained due to adsorption of ammonia molecules on silver film surface. According to detected and measured interference maximum shifts up to 14 nm in transmission spectra of Al2O3 + Ag membranes in ammonia gas flow, the possibility of constructing a selective interferometric optical sensors with 10 − 15 min response time is shown.

Experimental results related to the photoactivated dc conductance of anatase TiO₂ nanotubular arrays (aTNTAs) under pulsed irradiation by a laser light inside and outside the fundamental absorption band are presented. It is found that the mobility and diffusion coefficients of charge carriers in the examined aTNTA are extremely low due to a strong charge-phonon coupling, abundance of shallow traps, and hopping conductivity between adjacent nanotubes. We consider that the confining electric field appeared within the array structure due to the difference in the local concentrations of excess electrons and holes at large values of the dc conductance suppresses the drift current. In this case, the dc conductance of such aTNTAs is mainly matured by the diffusion of mobile carriers. A recurrent kinetic model for evolution of the dc conductance of aTNTAs under laser irradiation has been proposed to interpret the experimental results.