Physics, Chemistry and Application of Nanostructures

FOREWORD.

CONTENTS.

First-principles ground-state calculations on different kind of materials are currently carried out within density functional theory. On the other hand a correct description of the electronic excitations, which are at the origin of many experimental spectra, requires more refined theories. In this paper we summarize the main equations of the theoretical many-body approach used to describe electronic and optical properties of real materials. Some examples of excited state calculations in bulk and low dimensional semiconducting systems are given.

Germanium quantum size films and wires have been investigated regarding their electronic and optical properties. Ab initio calculations within the linearized augmented plane wave method have been employed for this purpose. Quantum confinement is found to shift the fundamental band gap of the bulk germanium to the blue energy range. The value of the upshift as well as the nature of the gap depends strongly on the surface symmetry. Strong direct gap absorption in the visible energy range has been predicted for germanium quantum films and wires.

3D opal nanocomposites or photonic crystals represent a new category of materials for nanoelectronics and optoelectronics. The results are presented on novel nanocomposites with optical and magnetic active clusters in intersphere voids of 3D cubic opal structures consisting of SiO₂ nanospheres.

The paper summarizes our experimental results in the development of nanostructured novel optical coatings. Examples include metal island films and grating waveguide structures. Their application potential as building blocks for narrowline reflectors and spectrally selected absorbers is demonstrated.

Metal nanoparticles interact strongly with their immediate nanoenvironment. Nanoparticles absorb energy from surface bound fluorescent molecules but also change their radiative rate. Hence, fluorophore/gold-nanoparticle composite systems are promising resonant energy transfer pairs. Furthermore, a change in the refractive index of the surrounding shifts the scattering spectrum of the nanoparticles. This can be used in a single gold nanoparticle biosensor, which is sensitive to approx. 100 protein molecules.

PbS nanoparticles have been prepared via a colloidal route and were incorporated into silica-titania or hybrid organic-inorganic sol-gel films. X-ray defraction showed the presence of crystalline particles with 3-4 nm diameter. Strong quantum confinement was revealed by the large blue shift of the optical absorption offset. Strong photoluminescence emission was found when pumping at 514 nm. A saturated optical non linearity was observed with a nonlinear refractive index n₂ of the order of 10⁻¹¹ cm²/W.

We fabricated nanodevices based on a composite PMMA/H₃SiW₁₂O₄₀ system and investigated the effects of electrode material, electrode distance and molecular concentration on the electronic transport characteristics. It is found that in the case of electrode distances smaller than 50 nm, tunneling effects appear, which are discussed using tunneling theory models. These effects are primarily dependent on the electrode distance and molecular concentration and less on the electrode material.

Electrochemical doping of nanocarbons is an elegant alternative to chemical doping with redox active molecules. Single-wall carbon nanotubes (SWCNT), fullerene peapods (C₆₀@SWCNT, C₇₀@SWCNT) and double-wall carbon nanotubes (DWCNT) have been studied in detail during the last 5 years. The favorable features of electrochemistry consist in precise control of the doping charge and large variability in the selection of counterions compensating electronic charge at the carbon nanostructure. The optical and Raman spectra of nanocarbons acquired in situ reflect complex feedback to electrochemical tuning of the population of electronic states near the Fermi level. This allows the addressing of fundamental questions about the electronic structure and physical properties of carbon nanotubes and related species. Besides aqueous and aprotic electrolyte solutions, ionic liquids are readily applicable for Vis-NIR and Raman spectroelectrochemistry of nanocarbons in a broad interval of electrochemical potentials. This paper reviews the salient data, acquired on optical and Raman spectroelectrochemistry of SWCNT, fullerene (C₆₀, C₇₀) peapods and DWCNT.

We calculate nanocrystal excitation energies using a ΔSCF method with occupation constraint, thus including both self-energy and Coulomb effects. We find the well-known r^-1 dependence. The energies are found to follow the pressure dependence of the relevant gaps in the bulk materials; while Ge nanocrystals have a positive pressure dependence, the contrary holds for Si. For the pressure dependence of the excitation energies in Si_xGe_1-x nanocrystals, we find the transition from Ge-like to Si-like behavior at a composition of about x=0.3.

We present a study of the electronic structure and optical absorption spectra of Si(Ge)-capped Ge(Si) nanocrystallites (NC's) by means of ab initio pseudopotential plane-wave calculations. In certain aspects the capped Si(Ge) NC's are similar to the analogous Si/Ge heterojunctions. A compensation effect involving the overall composition of the nanocrystallite and quantum confinement effects is predicted for the Si-capped Ge NC's.

We investigate ultrafast nonlinear optical properties of periodic structures based on ZnSe/ZnS using interband and two-photon excitation of ZnSe sublattice by ultrashort laser pulses. A considerable shift of reflection spectrum and large relative reflection changes were observed in a wide spectral range corresponding to the transparency region of ZnSe far from the intrinsic absorption onset. Large relative reflection changes were observed in a wide spectral range. The nonlinear refraction is supposed to be controlled by population induced absorption changes in ZnSe. The relaxation time is controlled by a transition from non-equilibrium to quasi-equilibrium distribution of electrons and holes.

Molecular structure and frictional properties of self-assembled monolayers formed at the interface between reconstructed Au(111) surfaces and liquid n-alkanes (C_nH_2n+2, n = 10, 12, 14, 16) have been studied by scanning tunneling microscopy and friction force technique. We show that under the regime of boundary lubrication, kinetic friction coefficient, μ, strongly depends on the length of the alkane molecule. With increasing C_nH_2n+2 chain length from n=10 (decane) up to n=16 (hexadecane), μ decreases from ~1.7 to ~0.35. The variation of μ is related to the dramatically lowered sliding force for the molecules with a length close to the coincidence period between the -CH₂-CH₂- chain (period ≈2.51 Å) and the atomic rows on Au(111) oriented along the <110> direction (period ≈2.88 Å).

We have investigated the carrier capture and relaxation processes in InAs/GaAs self-assembled quantum dots (QDs) at room temperature by a photoluminescence (PL) up-conversion technique. We found that the carrier capture rate is faster than the intra-dot relaxation within the range of excitation densities that we have investigated. Under high excitation intensity, the electronic states in the dots were populated mainly by carriers directly captured from the barrier. However, at low excitation densities, the PL rise times were influenced by the carrier diffusion.

Thin layers of SiGeSn alloys were deposited on (001) Si wafers by MBE followed by thermal treatment at 600-1000°C for 10-150 min in N₂ or O₂ atmospheres. Based on TEM and RBS investigations, we report on phase separation and Sn surface segregation after treatment in an N₂ atmosphere. Formation of Ge_1-xSn_x crystals, however, takes place during oxidation of SiGeSn alloys. The Ge_1-xSn_x crystals are of nanometer size and of lens-like or sphere-like facetted shape. The formation of Ge_1-xSn_x crystals takes place as a result of Sn and Ge segregation at the moving SiO₂/Si interface.

The photoluminescence of nanocomposites doped with erbium and other rare earth elements is studied versus the concentration of rare earth ions. The optimum ratio of rare earth ions in opal nanocomposites is defined.

A new technique for measuring the nonlinear refractive index and absorption coefficient of thin film structures is presented. It is based on the analysis of the two-dimensional spatial intensity distribution of the reflected laser beam in excitation of the lightmode in nonlinear dielectric structures doped by CdSe nanocrystals.

Metal nanoparticles in an active part of an electroluminescent cell possess to increase the average electric field inside the cell and, as a consequence, electroluminescence brightness and efficiency, and to decrease the threshold of electroluminescence, due to improving conditions of electron tunneling as a result of potential barriers shape change. The role of electron warming up into molecule excitations is not essential.

The local fields influence on the strong coupling regime between an isolated quantum dot (QD) and monochromatic field has been theoretically investigated. Bifurcation and anharmonism in the Rabi oscillation dynamics has been revealed. It has been obtained that as a result of the local field influence quantum dot photoluminescence spectrum demonstrates a generation of additional satellites that correspond to the higher orders of the Rabi frequency.

Bleaching relaxation in PbS quantum dots of various sizes under different pump intensities has been studied. The observed bleaching relaxation features are explained in the context of the proposed spectroscopic model. The model takes into account transitions of excited charge carriers both in the system of quantum-confined energy levels and defect trap states of the dots. Characteristic times of direct electron-hole recombination, carriers trapping to defect states as well as cross-sections of “ground-state” and “excited-state” absorption of carriers can be evaluated from the experimental data using this model.

Treatment of helium implanted silicon at up to about 920 K under enhanced hydrostatic pressure (HP, up to 1.2 GPa) of Ar results in a creation of buried nano-structured layer composed of thin walled helium-filled cavities and bubbles. The Si:He samples treated at even higher temperature indicate the presence of disturbed/dislocated buried zones. HP affects diffusivity of implanted atoms and of defects produced at implantation and promotes creation of smaller cavities and of other extended defects near the range of implanted He.

The micro-Raman and photoluminescence (PL) spectra of colloidal CdTe nanocrystals deposited on a spherical microcavity are reported. Due to the feedback of the light trapped in the microcavity, a strong enhancement of the Raman signal is obtained. Periodic structure with very narrow peaks in the Raman spectra of a single microsphere was detected both in Stokes and anti-Stokes spectral regions, arising from the coupling between the emission from nanocrystals and spherical cavity modes.

We have studied optical properties of 3D confined photon states in a photonic molecule (PM) formed from two melamine-formaldehyde (MF) spherical microcavities containing CdTe nanocrystals. Utilizing different excitation conditions we have detected space-selective optical switching effect, the splitting of the resonances originating from bonding (BN) and anti-bonding (ABN) branches of the photonic states and fine peak structure resulting from lifting of the mode degeneracy.

It was shown that by using especial interruptions during growth of InGaN quantum dots (QDs) carrier localization in the QDs can be significantly enhanced. Deviation from nonequilibrium carrier distribution was revealed at the temperatures up to 600 K. In this case peak position behavior does not obey the σ²/k_BT law in contrast to the structure with shallow QDs.

We have studied optical properties of nanoporous metal polaritonic crystal surfaces. Reflection spectra of such surfaces in the framework of the self-consistent electromagnetic multiple-scattering layer-KKR approach have been calculated. Two types of plasmon excitations on the surface of nanoporous polaritonic metal crystals were investigated: surface plasmon-polaritons excited at the planar surface of metal and Mie plasmons in the lattice of voids buried in metal just beneath the surface. Special attention has been given to the coupling effects between these two types of plasma oscillations.

Structures of silicon nanocrystals in erbium-doped silicon dioxide (nc-Si/SiO₂:Er) exhibit efficient photoluminescence of Er³⁺ ions at 1.5 µm. The population inversion of Er³⁺ energy states can be achieved under strong optical pumping because of the energy transfer from the excitons in Si nanocrystals to the ions. The results obtained are discussed in view of possible applications of nc-Si/SiO₂:Er structures in optical amplifiers and lasers compatible with Si-based technology.

We investigate the amplitude of mesoscopic fluctuations of the conductance of a semiconductor two dimensional electron gas mesoscopic junction at arbitrary bias voltage. The oscillation features of the conductance with the magnetic field are predicted to be due to quantum interference of electron waves.

Artificial optical media based on nanostructured silicon fabricated through electrochemical porosifying of Si substrates are investigated. The strong optical anisotropy in the infrared and visible spectral ranges is found and discussed in the framework of a model of anisotropic silicon nanocrystals. The observed absorption anisotropy of surface vibrations agrees with the model proposed.

In this paper we introduce a novel structure of waveguide quantum wires, which is the binomially tailored sequence of Dirac delta function potentials with binomial distribution law. We have assumed scattering of electrons solely from the geometric nature of the problem. The transmission through the quantum wire in the allowed band is almost the unity without any ripple after some small kd/π values, which is an interesting feature of this structure.

The field emission from the semiconductor 2D layer was discussed taking into account the finite depth of the potential well and normal to the surface electron velocity distribution. The current density of the field emission as a function of the layer thickness and temperature was calculated in quasi-classical approximation.

A novel method of laser electrodispersion, based on cascade fission of microdrops charged in laser torch plasma was used for fabrication of monodisperse Ni nanostructures consisting of one or several monolayers of amorphous Ni grains covered by an oxide layer. Optical and conductivity properties of Ni nanostructures formed in a magnetic field reveal a strong anisotropy, which is determined by the structural characteristics.

For the first time, superlattices in the Ga_0.8In_0.2As–GaAs system have been grown using Si and C for quasi-δ-doping by the metal-organic hydride epitaxy method. At low-temperature photoluminescence of the superlattices, the edge band of 1.488 eV related to recombination in the GaAs layers and a weak peak of 1.15 eV, which is associated with transitions in the Ga_0.8In_0.2As quantum wells are observed. In the long-wavelength part of the spectrum the intensive tunable structural band with the maximum at 0.9 eV is found as well. This band displays changes in the potential relief of the hetero-superlattice under the excitation.

The photoluminescence (PL) parameters for the same CdSe/ZnS nanoparticles in aqueous solutions and on the surface of silanated glass are compared. As it is revealed, chemisorption and assembling of nanoparticles in 2D ensembles not only leads to an increase in PL quantum yield, but also prevents PL quenching in a polar environment.

We report on sol-gel synthesis of Eu- and Er-doped garnets in porous anodic alumina, revealing the strong luminescence in visible and near IR ranges associated with the ⁴I_13/2→⁴I_15/2 and ⁵D₀→⁷F_j (j=1, 2, 3, 4) transitions of trivalent Er and Eu ions, respectively.

Silicon molecular beam epitaxy atop β-FeSi₂ nanosize islands with density of 5·10⁹ cm^-2, grown on Si(111)7×7 surface and Si(111)-Cr surface phases, have been observed at 800 °C by LEED and atomic force microscopy. It was shown, that silicon thickness 0.1 µm is not enough for a full burying of iron disilicide clusters in silicon. It was revealed from in situ electrical measurements that the minimal influence on electrical properties of the silicon layer render iron disilicide clusters grown on Si(111)7×7-Cr surface phase.

Strong 1.54 µm photoluminescence response retaining its sharp pronounced features at room temperature has been obtained from the erbium doped Fe₂O₃ xerogels fabricated on porous anodic alumina films. The luminescence behavior and availability of these structures for future photonics applications are discussed.

Two types of the samples comprising erbium doped titanium xerogels were fabricated on porous silicon and porous anodic alumina. Strong 1.54 μm luminescence from the structures is reported and discussed.

Er-doped nanosize silicon structures have been fabricated by magnetron sputtering of a composite target (Al + Er₂O₃ + Si) and its electrochemical anodization at room temperature. The fabricated structures have been investigated with secondary ion mass spectrometry and electroluminescence measurements. The 1.53 μm electroluminescence peak at high current was attributed to Er³⁺ ion light emission. The high value of the pick width can be explained by the dislocation related electroluminescence observed in the investigated structures too.

Room temperature, green photoluminescence from erbium-doped titania and indium-tin oxide xerogel films confined in porous anodic alumina has been examined. The dependence of the photoluminescence intensity and the shape of the spectra on xerogel composition, erbium concentration and degree of pore filling is shown.

The sol-gel technique was developed for preparation of silica glasses doped with europium and copper selenide nanoparticles. Their luminescence behavior was studied. The features of luminescence of europium in the co-doped materials are interpreted as an energy transfer between copper selenide nanoparticles and Eu³.

The technology of solid-phase growth of one-layer and three-layer structures with buried magnesium silicide (Mg₂Si) clusters with nanometer sizes and density of 2·10⁹ cm^-2 has been developed. According to the data of AFM and far IR spectroscopy, Mg₂Si islands remain in depth of the Si layers at 650 °C. A contribution of buried magnesium silicide clusters in Si to the optical functions is observed at 0.5-2.5 eV. The huge increase of a Seebeck coefficient (in 50-180 times) for samples with buried Mg₂Si clusters in comparing with one for the bare p-type silicon substrate has been observed.

Transmittance and photoluminescence of SiO₂ opaline photonic crystal with HEuEDTA molecules embedded into it were studied. Angular distribution of the emission intensity and changes in structure of Eu³⁺ emission bands were observed.

Temperature dependence of photoluminescence(PL) from CdS nanoclusters formed in the matrix of a Langmuir-Blodgett film has been investigated. At room temperature the PL spectrum of nanoclusters in the matrix has a band with a maximum at 2.2 eV. After removing the matrix by heating in vacuum the PL spectra consist of a high energy band at 2.9 eV and lower energy band at 2.2 eV. After heating a sample in NH₃ the PL spectrum consist of three bands, the intensive high energy band at 2.7 eV and two low energy bands at 2.2 eV and 1.8 eV. Temperature dependence of the maximum of the high energy band at 2.9 eV can be described by the empirical Varshni formula with the coefficient α=4·10^-4 eV/K (for bulk cadmium sulfide crystal α=8·10^-4 eV/K). This decrease of α is explained as a reduction of the electron-phonon coupling potential in the quantum confined nanoclusters.

Current methods for synthesizing and studying nanochannel structures based on Al₂O₃, SiO₂ and polymers are discussed in this paper. Processes of self-organization provide the ordered patterns of such nanocapillaries. Potential applications of these nanochannel structures and ordered carbon nanotube arrays grown on them are treated.

Simple approach based on the effective mass theory has been developed and successfully applied to simulate thermoelectric properties of monocrystalline and grained nanocrystalline films accounting for the confinement effect and interactions between the grains. Thermoelectric efficiency was evaluated in the wide temperature range from 50 to 900 K. Quantum confinement was found to influence figure of merit (ZT) values only for the films with the thickness less than 5 nm. The highest ZT values varied from 0.63 to 0.72 depending on the film thickness as well as on the lateral size of grains. Inclusion of the grains inside the film induces a considerable increase of the bend gap and decrease of the thermal conductivity as compared to the monocrystalline film of the same thickness.

A 3D Monte Carlo study of electron transport in GaAs/AlGaAs superlattices exposed to static and high-frequency fields is presented. We analyze an effect of electron interfacial roughness scattering on an amplification coefficient of superlattices with different miniband widths at low temperature (10 K). We show that electron scattering at optic phonons prevents strong suppression of the Bloch gain caused by superlattices interface roughness.

The method is proposed to form of azimuthally and radially polarized Bessel light beams based on the interaction of radiation with layered periodic medium containing defects. The possibility to control the given process by variation of cone angle of an incident light beam is demonstrated.

Single-electron states in a quantized cylindrical layer for the case of finite confining potential are observed. The transcendental expressions are derived within the effective-mass approximation. They allow to obtain the energy spectrum and envelope wave functions of transversal motion of charge carriers in the layer. The dependence of energy levels on the size of the system and effective masses of carriers is shown for the GaAs/Ga_1-x Al_xAs/GaAs heterostructure.

The new form of size distribution function of small nanoclusters is obtained by means of the principle of maximum information entropy. Surprisingly, for saturated and supersaturated vapor this function is not a monotonic one. It was shown that normalization constant of this distribution function depends on supersaturation in the system. Some new results of calculation of nucleation rate of graphite-like carbon clusters are presented. The transition to barrierless nucleation of carbon clusters is predicted for relatively small supersaturations.

We demonstrate the inapplicability of standard weak-coupling-based van der Waals interaction models in a close vicinity to a nanotube surface.

The interaction of a single-wall carbon nanotube (CNT) with the external electromagnetic field has been investigated theoretically on the basis of the quantum kinetic equations for π-electrons in CNT. The quantum kinetic equations have been solved analytically by the perturbation method and the third-order polarisabiliy in CNT has been calculated. The comparison of the obtained results with the data of the pump-probe measurements has been performed. The good agreement with the experiment has been obtained.

Optical spectra of Au/C₆₀ planar nanostructures fabricated by the combined evaporation of gold and fullerenes are studied in the visible and near infrared spectral regions. Dependence of the Au surface plasmon absorption band on surface density of gold and fullerenes is discussed in correlation with structure parameters and electron/photon confinement conditions.

The rate of electron-phonon energy transfer at low temperatures has been calculated within the framework of the tight-binding model for the electron spectrum of single-wall “armchair” carbon nanotubes. This rate is proportional to T²(T − T₀), where T and T₀ are the electron and phonon temperatures.

The paper describes reproducible creation of probe tips of carbon nanotubes for a use in an atomic force microscope (AFM). Existing ways of the AFM probe tip modification have been reviewed. Experiments implementing two selected approaches: growing of nanotubes on the tips and transfer of carbon nanostructures on to the tip from a suspension. TEM and AFM analysis showed that the precalibrated carbon nanostrucures are advantageous for the probe tip modification.

We report here on the platelet surface morphology changes and platelet aggregation as a function of time after addition of 10^-5 M ADP and 5·10^-3 M H₂O₂ to cause reversible platelet aggregation by scanning force microscopy. Different stages of the platelet shape change from the initial formation of filopodes to slowly reverting back to discoid shape platelets were investigated. The periodical chain-like structure with irregular size of 40-55 nm and fiber structure with the width of ~ 3 nm on the filopodia surface were observed. Analysis of the activated platelet surface morphology reveals details of the cytoskeleton rearrangement.

On the basis of the volume integral equation formalism we have developed the method for calculation of local fields inside and near the surface of particles, including particles of complex shape metallic spherical and cylindric nanoparticles. Numerical simulations were made for bispheres and shell-coated spheres in the spectral range close to the surface plasmon absorption resonance of copper and silver. A high sensitivity of near-field characteristics to the shape and internal structure of metallic nanoparticles examined is shown. Characteristic regions of “hot spot” localization and local field attenuation coefficients are determined.

We present examples of the use of AFM devices produced by NT-MDT for characterization and investigations of a large scale polymer morphology, the study of polymer melting and crystallization with a molecular and submolecular resolution.

In this work a new technique for domain imaging in ferroelectric materials is shown. A combination of scanning electron microscope (SEM) and atomic force microscope (AFM) in which the electron beam and the cantilever interact with the sample simultaneously is used. Since both are acting only at the sample surface, surface acoustic waves (SAW) are generated and detected. With these waves the ferroelectric domain structure in BaTiO₃ can be made visible.

We present a theoretical study of spin transport in semiconductors in a drift-diffusive regime. The electron spin motion is defined by a modified spin length, which is strongly dependent on current density. The evaluations made for the case of moderately doped n-type silicon (n~10¹⁶ cm^-3) gives the diffusion length as high as several microns at room temperature. We emphasize also the difference between the electron spin polarization and current polarization. The study of spin transport through a n/n+ junction shows that in contrast to the ferromagnetic metal/normal metal junctions, the conductivity mismatch has no impact on the current polarization, but strongly affects the carrier polarization.

The quasiclassical theory of a nanosize point contacts (PC) between two ferromagnets is developed. The maximum available magnetoresistance in PC is calculated for ballistic and diffusive transport at the area of a contact. In the ballistic regime, the magnetoresistance in excess of few hundreds percents is obtained for the iron-group ferromagnets. The regime of quantized conductance through the magnetic nanocontact is considered. It is shown that magnetoresistance is tremendously enhanced at small number of open conductance channels. The quantum spin valve realization is discussed in detail, and recent observations of huge (up to 100 000 %) magnetoresistance in the electrodeposited nickel nanocontacts are discussed in the framework of the developed theory.

The theory of nanosize point contacts made of ferromagnetic metals is developed. A general quantum scattering theory is applied to calculate conductance of the nanocontact with domain wall located in the constriction. Exact solution of the electron motion in the potential of the linear domain wall is used as a zero-order approximation. Spin-conserving and spin-flip conductivities are calculated by perturbation theory up to the second order in difference between the model and actual potentials of the domain wall. The spin-flip conductivity imposes natural limitation on magnetoresistance of a point contact, which otherwise diverges in the regime of quantized conductance through the contact.

We propose two types of low-dimensional current sources supplying spin-polarized charge carriers. One of them is based on the magnetic subband depopulation effect in a quantum wire made of a semiconductor, placed in a magnetic field. The other one employs a quantum point contact in a diluted magnetic semiconductor. The quantum mechanical model describing transport of charge carriers in these structures was developed within Green's function formalism. Operation of the quantum wires and the quantum point contacts as sources of spin-polarized currents are discussed. They are predicted to provide 80-100 % of spin polarization in a single-mode regime.

We studied effects of domain wall pinned at nanoconstrictions created in ferromagnetic Ga_0.99Mn_0.01As layers on their magnetoresistance (MR). Negative MR observed at 1.5 K is likely dominated by the suppression of weak localization (WL) in a magnetic field. In constricted samples, additionally, jumps of an enhanced conductance appear, whose positions reflect the hysteresis loop of magnetization. We argue that these are manifestation of the suppression of WL due to the nucleation of a domain wall in the constriction.

We have studied the electron transport and have observed a new phenomenon, the positive injection magnetoresistance in heterostructures GaAs/granular film where the granular film is either SiO₂ with Co nanoparticles or TiO₂ with Co island layers. A theoretical model of the effect is based on surmounting of injecting electrons on potential barriers in the spin-polarized accumulation electron layer, which is formed in GaAs near the interface.

Electrical transport properties of LCMO/YBCO/LCMO trilayers have been studied by resistivity versus temperature measurements in external magnetic fields up to 8 Tesla. The samples were characterized by similar LCMO thickness and different YBCO thickness. The experimental results show resistive transitions which reflect different properties of the samples related to the role of the magnetic LCMO on the differently thick YBCO layers.

The angular dependence of the upper critical magnetic field, H_c2(Θ), for Nb/Pd proximity coupled multilayered nanostructures with a thickness of Nb and Pd layers of the order of the superconducting coherence length were investigated. We show that the deviation of the experimental data from the theory is temperature dependent. The performed precise analysis reveals the existence of an angular and temperature range where the deviations reach their maximum. The obtained results indicate that the parameter of the localization of the superconducting wave functions could be appropriated for describing the H_c2(Θ) curves.

Magnetic force microscopy (MFM) was used to study domain structures in micron-sized stripes of a cobalt film of 40 nm thickness. The observed MFM images were used to set a sketch of domain structure (initial magnetization) for computer simulations. Micromagnetic calculations were performed using web-version of the NIST software.

We demonstrate MFM (magnetic force microscopy) tip induced remagnetization effects in ferromagnetic elliptical nanoparticles varying in thickness, size and aspect ratio. These arrays of particles are produced by interference laser lithography and e-beam lithography methods. It is found that Fe-Cr particles with a high aspect ratio show reversible switching of the single domain magnetization state. At the same time, Co nanomagnets with a low aspect ratio exhibit tip induced transitions between the single domain and the vortex state of magnetization.

A systematic theoretical study of electronic and spin properties of various carbon nanoclusters has been done using ab initio (Hartree-Fock, DFT) and semiempirical (PM3, AM1) quantum-chemical methods. We have studied two classes of carbon nanoclusters with embedded [NV]⁻ defect center: (i) the hydrogen passivated C₃₆H₄₂[NV]⁻, C₆₉H₈₄[NV]⁻, C₈₄H₇₈[NV]⁻ nanoclusters and (ii) the nonpassivated C₃₆[NV]⁻, C₆₉[NV]⁻, C₈₄[NV]⁻ clusters. The study of spin properties for the defect-embedded carbon nanoclusters was done for the first time. The geometrical cluster structures were optimized by the total energy minimization. The passivated carbon nanoclusters were shown to be relaxed to the diamond-like structures. Contrary, non-passivated clusters exhibited reconstruction to fullerene-like structures in the form to be depend on number of atoms in the clusters and the initial geometry. For the [NV]⁻-defect-embedded hydrogen passivated clusters the simulated spin density was localized at the carbon atoms, which are the nearest neighbors to the vacancy. In the case of nonpassivated clusters the spin density was localized at the nuclei of the surface atoms.

The magnetic breakdown development under uniaxial stress has been detected for the first time in 2D hole gas at p-GaAs/Al_0.5Ga_0.5As heterointerface. The effect is connected with the specific character of the Fermi surface transformation.

The method of differential reflection spectroscopy (DRS) has been applied to study thin iron films during their growth on Si(111) or Si(100) surfaces at room temperature (RT). Some details on the dynamic standard method in DRS method are given. A dependence of dielectric function of the films on the deposit amount is presented. The difference is shown between the iron films grown on Si(100) and Si(111).

A quantum calculation cluster containing silicon magnetic isotope chains on a step surface of a silicon substrate as a qubit ensemble is proposed. The resonance frequency separation between chains of silicon magnetic isotope nuclear spins is realized with a gradient of magnetic field and the nuclear spin polarization is achieved by the excitation of electron transitions in nanosize silicon regions. It is shown, that the ensemble qubit resonant frequency separation in the cluster is effective in the region of 2.5-4.0 µm and at the distance between qubits of 2-3 nm. In this case the necessary magnetic field gradient is 0.04 T/µm.

We have designed and modeled a quantum computing cluster containing quantum indium wires on silicon (111) surface. Nuclear spin polarization is realized by excitation of electrons in paramagnetic centers on the silicon surface. Resonant frequency separation between the wires is achieved employing a gradient of external magnetic field. It is shown that effective separation of resonant frequencies for ensemble qubits in the cluster takes place when the distance between the wires is 0.8 nm and the magnetic field gradient ranges from 0.05 to 0.07 T/µm.

A general synthetic strategy for the synthesis of PbX (X = S, Se, Te) is introduced. The resulting material qualities of size and monodispersity are discussed with respect to the injection temperature, growth temperature, growth time and solvent mixture. Some material characterisation data gathered with the aid of transmission electron microscopy (TEM), X-ray diffraction (XRD) and optically using absorbance and emission spectroscopy are presented and discussed.

A series of double well quantum dots consisting of alternating CdS and HgS layers have been synthesized. The structures have been investigated with UV/VIS/NIR absorption and emission spectroscopy and transmission electron microscopy. Furthermore, the results of the optical spectroscopy are compared to theoretical calculations within the effective mass approximation.

Electrochemical studies of thiol-capped semiconductor nanocrystals in an aqueous solution have demonstrated several distinct oxidation and reduction peaks in the voltammograms, with the peak positions being nanocrystal size dependent. It has been demonstrated that the method is very sensitive to the nanocrystal surface state, providing complementary information for better understanding of special optical properties of semiconductor nanocrystals.

A new method for modifying substrate surfaces has been developed: preliminarily aminated substrates of various compositions and shapes are linked with water soluble high luminescing CdTe nanocrystals through the formation of an amide bond between the carboxylic groups of mercaptoacid-capped nanocrystals and the amino groups of the substrates.

To fabricate a well-ordered monolayer of CoPt₃ nanoparticles that covers large areas a spin coating technique was used. Prior to particle deposition poly(vinyl pyridine) (PVP) and poly(ethylen oxide) (PEO) were used as surface modifiers of oxidized silicon wafers. Grazing incidence small-angle X-ray scattering, atomic force and electron scanning microscopy were used to characterize the polymer and particle layers and to study the influence of polymers as substrate modifiers on the particle packing.

A reduction of GeO₂ towards Ge within GeO₂ and SiO₂-GeO₂ thin films was studied. Spectral-luminescent features of the films were investigated. Luminescence with λ_max=445 nm was observed for Ge-SiO₂ films on excitation with the light of λ=280 nm.

Two different components were introduced in the polyelectrolyte multiplayer shells of capsules – either Ag-nanoparticles or IR-dye – to induce absorption of light. Under laser illumination the capsules containing Ag-nanoparticles or IR-dye were deformed or cut, thus providing a venue for remote release of encapsulated materials. The experiments were conducted with a low power near infra-red continuous wave laser diode.

CulnSe_2xTe_2(1-x) nanoparticles of the ten-nanometer size range were fabricated within silicate glass matrices distinguished by alkali components. The type of the glass matrix has an essential effect upon production of the solid solutions with variable x. Optical features of the glasses depend also on Se/Te ratio and do not reproduce the bulk counterparts. These variations are considered as a result of phase transformations, which deviate properties of the particles with a selected composition from the original ones.

In solutions of variable polarity at 77-293 K, non-covalent binding interactions via the key-hole scheme “Zn–pyridyl” have been used for the formation of porphyrin triads and pentads as well as for the surface passivation of pyridyl–substituted tetrapyrroles on the core– shell semiconductor CdSe/ZnS quantum dots (QDs). CdSe/ZnS QD emission quenching by attached porphyrins (due to energy and/or charge transfer) depends strongly on the number of anchoring groups, their arrangement in the porphyrin molecule as well as on QD size and number of ZnS monolayers. Simultaneous presence of porphyrin triads/pentads and QDs in a solution leads to an equilibrium competition between multiporphyrin complex formation (complexation constant K_C ≈ 2·10⁷ M⁻¹ for 1:1 interaction) and appearance of CdSe/ZnS QDs passivated by pyridyl–substituted porphyrins (K_C ~ 10⁷ M⁻¹ for one QD and number <n> of porphyrin molecules).

Ag films obtained by RF magnetron sputtering are X-ray amorphous. They yield pseudospherical nanoparticles of γ-Agl upon iodization as seen by SEM. The disorder induced by the sputtering process apparently favours controlled growth of γ-Agl nanoparticles as seen by sharp and characteristic excitonic features. The kinetics of AgI formation from disordered Ag is being explored.

Preparation of particles consisting of the dielectric core (MnCO₃, MnO₂) and the metallic shell (Ag, Ni) is proposed. Their potential application as microwave absorbes is outlined.

Fast oxidation of porous silicon in air was found to manifest itself as a combustion or an explosion. The combustion process takes place in porous layers with a thickness smaller than 60 µm, while the explosion is observed in thicker layers. The explosion is supposed to develop via thermal overheating due to an exponent increase of the reaction rate with the temperature rise.

Size, shape and optical properties of silver nanoparticles in photosensitive layers on the basis of AgHal in the redox-dispergation process are considered. The significant effect of particle shape and aggregation on colour and absorption spectra of the layers, containing specified particles is emphasized.

Formation of silver alcosols by the destruction of Ag(I) complex (synthesized by us) with 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]-acetic acid in alcohols (methanol, ethanol, propanol-2, butanol-1) was studied. Size and assembling of silver nanoparticles in alcosols were examined by means of absorbance spectroscopy, TEM and AFM.

The methods of nanosized gold particles formation are developed using tetrachloroaurate ion reduction with sodium borohydride in the presence of high-molecular (HM) and low-molecular (LM) stabilizers compatible with living organisms. The most stable sols with 2-3 nm particles and high monodispersivity are formed with HM stabilizers such as PVA, gelatin, PVP. Correlations have been found between stability of sols and the ξ-potential. The most stable sols have the ξ-potential of (60-76) mV.

It is shown that the adsorption of Sn(II) compounds proceeds by chemical mechanism when ion exchange with carboxyl groups is realized on the polyimide film from the acid and not aged SnCl₂ solutions and by physical mechanism which includes colloidal particles sticking on the alkali silica glass from the acid and alkaline, freshly prepared and aged solutions. The adsorbed nanoparticles fulfill the function of the growth centers. It is determined that only chemical adsorption can provide the formation of island-type uniform monolayer film, which consists of the particles 5-10 nm in sizes at a quantity of 300-600 µm⁻² and covers the dominating part of the substrates.

Experimental studies show the interaction between FeCoB nanoparticles with different stabilizing agents. Magnetic nanoparticles of complicated structure with active functional groups on the surface are obtained. All samples are characterized with TEM, XRD, IR-spectroscopy and electron spin resonance technique.

Present work demonstrates the possibility to use the oxide nanoparticles as a reservoir for the storage and prolonged release of the corrosion inhibitor offering the effective self-healing properties. The zirconia nanoparticles not only reinforce the hybrid matrix but also absorb inhibitor ions releasing them during contact with moisture. The “intelligent” release of the inhibitor provides long term corrosion protection of the metallic substrate compared to the case when the inhibitor is added to the sol-gel matrix.

Nanocrystalline Ce_0.45Zr_0.45La_0.10O_2-δ powder was prepared by organic-free modification of the sol-gel technique. Crystallization of amorphous precursor starts at 600 °C and results in the formation of highly dispersed (4÷5 nm) cubic fluorite solid solution, stable up to 1100 °C. The ESR studies showed that the incorporation of La(III) into the Zr_0.5Ce_0.5O₂ lattice leads to increasing concentration of Ce³⁺ defects. This may contribute to the high catalytic activity towards partial oxidation of dry methane. The methane oxidation on composite Ce_0.45Zr_0.45La_0.10O_2-δ/Pt anodes in a model SOFC-type reactor provided 73 % CO selectivity with 54 % conversion efficiency at 900 °C and CH₄:O₂ ratio equal to 2.

According to the experimental results obtained by XRD, ESR and TEM, the inorganic sol-gel technique of CeO₂-ZrO₂-Al₂O₃ synthesis is shown to be the worthwhile method to produce materials with catalysis demanding properties. The conversion of precipitate into the colloidal state results in an increase of thermal stability, phase homogeneity and dispersity of the final products.

A number of nanostructured phosphate-oxide composite materials based on titanium dioxide has been synthesized and investigated for photocatalytic applications. Aluminum phosphate AlPO₄, titanium phosphate TiOHPO₄ and hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ were used as support materials for the deposition of nanocrystalline titanium dioxide. The enhanced photocatalytic activity of these composite materials is due to the combination of a very high specific surface, chemical stability, minimal concentration of recombination centers in mesoporous phosphate matrixes, and the presence of anatase-enriched titanium dioxide nanoparticles.

Nanostructured alumina fibers prepared by impregnation of polymer fibrous material with aluminium salt solution followed by heat treatment posses a high adhesion to alumochromphosphatic binder (ACPB). The main technological factors affecting wetting and impregnation are the solution viscosity and fiber texture. The role of these factors predominated over another parameters: composition, fiber specific surface and ACPB surface tension. A thermally resistant composite material was prepared by subsequent annealing.

The work deals with the study of porous silicon (PS) photoluminescence (PL) spectra changes as a result of adsorption on its surface of polynucleotides (DNA, poly(rA), poly(rU)) and mononucleotides (AMP and ATP). It was established that polynucleotide layers on the surface of nanocrystallites brings the appearance of a band of luminescence at room temperature with a maximum of 710-730 nm for PS samples, which initially did not produce PL in the visible region and increase PL intensity for the samples that had visible PL. PS with mononucleotide layers did not expose essential changes in PL spectra in the visible region.

We have developed the method for the synthesis of nanocrystalline hydroxyapatite gel in aqueous alkaline medium. The morphology and crystalline structure of nanocrystalline hydroxyapatite gel and xerogel has been investigated by SEM, AFM microscopy, FTIR spectroscopy and X-ray diffraction analysis. Hydroxyapatite gel has been used for the preparation of drugs and bioactive coatings for ophthalmologic implants.

Solid solutions of lanthanum manganites (1−x)La_0.75Sr_0.25MnO₃−xLa_0.6Pb_0.4MnO₃ were synthesized in air at 700 °C for 1 h by using the sol-gel method. Size of precursor particles, the specific magnetization of saturation and temperature of ferromagnetic-paramagnetic phase transition (Curie temperature) were investigated.

The potentiodynamic electrochemical frequency response of atomic layers underpotential deposition (UPD) shows different kinds of constituents in reversible and irreversible processes in a cyclic potential scan. The total response of reversible UPD decomposes into the constituent responses of double layer and Faradaic processes represented by adsorption capacitance and resistance in equivalent electric circuit (EEC). Anions that affect metal monolayer deposition give a separate RC branch in the EEC with characteristic R and C dependencies on the potential. The EEC of irreversible UPD does not contain adsorption capacitance. The Faradaic part of the response is revealed by charge transfer resistance and the Warburg impedance, showing hysteresis in cyclic scans. Nonideal double layer capacitance in the irreversible UPD is well represented by constant phase element.

Deposition of Cu on porous silicon (PS) by chemical corrosive treatment in copper sulfate and aqueous solution of hydrofluoric acid was investigated. It was defined that Cu deposits on PS surface as a nanosized grainy film. Distributive character of the deposited metal and factors that influence Cu film structure are described. It is shown that variation of the PS porosity and corrosive treatment time enable to create new nanocomposite PS-Cu structures.

The technique of photoelectrochemical preparation of In₂Se₃, CdSe, ZnSe and PbSe nanoparticles has been developed. The nanoparticles were produced by illumination of Se electrode at a cathodic potential in acidic solutions of corresponding nitrates. The average size of the particles was 40–80 nm. Nanoparticles were synthesised both at the Se cathode surface and in the electrolyte. The concentration of metal ions in the electrolyte was found to be the main controlling parameter of the photoelectrochemical reaction influencing the localization of the metal chalcogenide nanoparticles formed.

The mechanism of electrochemical formation of Cu_xSe_y on Se electrode as well as on Se rods has been studied. Copper electrodeposition onto Se occurs at potentials more positive than the equilibrium Cu²⁺/Cu⁰ potential. The interaction of Cu adatoms with selenium results in formation of Cu_xSe_y. High efficiency of copper diffusion into Se allows to control the deposition and produce not only nanoparticles on Se surface but also layers of nano- and micrometer thickness and bulk Cu₃Se₂ (Cu₂Se·CuSe) film. The Cu_xSe_y nanoparticles and nanolayers modify the Se surface and result in appearance of electronic surface states in Se bandgap, thus promoting electron exchange processes between the valence band and redox species in the solution.

The effect of a static treatment of polypropylene (PP) band by atmospheric pressure plasma in rare gases was investigated. The surface properties have been characterized by measuring the contact angle, frictional forces and topography exploration.

Well-aligned multi-wall type carbon nanotube (CNT) film was deposited on silicon and glass substrates by the radio frequency (RF) plasma assisted chemical vapor deposition (CVD) at the substrate temperature of 550 °C. The selective growth of CNTs was also demonstrated. The CNTs were 7 and 17 nm in the inside and the outside diameter, respectively. The RF plasma CVD is show to be a promising technique to grow the well-aligned carbon nanotubes on a large substrate at low temperature.

A novel paths for the fabrication of bio- and chemical sensors is introduced by using scrolled Si/SiGe heterostructures. In this paper, particular emphasis is put on the fabrication and stability of helical nanostructures. The shape of these structures, namely their helical angle, chirality, pitch and diameter are controllable in a reproducible fashion. The structures offer an excellent surface to volume ratio with easy access to the whole surface area.

The requirements for mass production of electronic and optoelectronic devices call for the expansion of MOCVD reactor capacity by the increase of the wafer number and size. Today, MOCVD reactors with capacities of 24×2 inch and 8×4 inch are readily available. Growth experiments on 4 inch wafers, however, require careful process and reactor hardware design since effects related to strain and resultant wafer bow are more pronounced in larger wafers.

Sintering of SnO₂, ZnO and Ga₂O₃ powders under argon flow leads to the formation of different elongated micro and nanostructures on the sample surface. Nanowires have been grown on the three materials investigated, while in the case of SnO₂. tubes were also obtained. The samples have been characterized by scanning electron microscopy (SEM) and by cathodoluminescence in the SEM. The nanostructures show different luminescence properties than the sample background. The luminescence properties of the elongated structures are discussed.

Electron-beam nanolithography with fullerite films was developed using different substrates. Fabrication of the ordered patterns with feature size in the range of tens of nanometres was demonstrated.

In the first part, we present an overview about a new family of electronic structures that makes use of ion irradiation, to induce electrical anisotropy in one of its components. These structures can, in principle, be scaled down to nanometric dimensions. In the second part, we summarize as an example our recent results on such a structure that contains an organometal.

Proximity effects have been observed during the formation of silicon oxide lines on silicon under the probe of an atomic force microscope. The essence of this effect is that the first line of the oxide creates a lateral barrier for diffusion of oxygen inducing an asymmetry in the cross profile of a subsequently formed nearby the oxide line.

MDM structures with a tunnel anodic oxide of aluminum were electrochemically fabricated. The offered technology has allowed producing a nanometer thin film dielectric layer with a vacuum evaporated top-metal electrode. The main features of the developed technology and main processing characteristics are presented.

Cadmium telluride (undoped and iodine doped) nanocrystalline thin films were prepared by spraying CdTe and CdTe:1 nanoparticles, dispersed in 1-butanol on the glass substrates. The nanoparticles were prepared using the solvothermal method. The presence of iodine in the films was confirmed by the sign of voltage generated (positive relative to the cold end) in the hot probe method and by XPS studies. The effects of iodine doping on the structural and surface morphology in these thin films are reported.

Two types of hollow structures – halloysite nanotubes and polyelectrolyte capsules are proposed as new nanoreactors for spatially confined synthesis of composite materials of core-shell type. Halloysite nanotubes are utilized as a biomineralization nanoreactor on example of the urease-catalyzed CaCO₃ formation. Precipitated CaCO₃ completely fills the inner nanotube lumen and exhibits the metastable vaterite-phase structure. Crystallization conditions inside polyelectrolyte capsules of 2.4 or 4 µm in diameter lead to the fabrication of crystalline fluorescent nanoparticles (La_0.95Eu_0.05PO₄, Ce_0.9Tb_0.1PO₄, and La_0.4Ce_0.45Tb_0.15PO₄), metal and metal oxide nanophase (Cu, Ag, etc.), and hydroxyapatite possessing high catalytic activity and surface area without additional thermal treatment.

Epoxy/clay nanocomposites were prepared using a so-called ‘slurry-compounding’ process. The amount of organic modifier used in this process is only 5 wt% of clay. The resulting epoxy/clay nanocomposites exhibit a high degree of clay exfoliation and dispersion, and show excellent thermal mechanical properties.

Silver–copper bimetallic nanoparticles were synthesized by pulsed laser ablation of the combined target. The target consisted of two tightly pressed silver and copper plates, immersed into the cell with liquid (acetone, water). Experiments were made by using two 10 Hz pulsed Nd:YAG lasers, operating at 1064 nm (IR) and 532 nm (green). Laser beams were focused on the Ag-Cu interface. The optical properties of the fabricated particles were found to be sensitive to the additional 532 nm laser irradiation. The experimental optical extinction spectra of the prepared colloids and post-irradiated ones were dependent on the production step sequence resulting in different types of nanoparticles, namely, segregated, alloyed or coated. The optimal conditions favoring formation of nanoparticles with a desired structure were found.

Different techniques for deposition of materials into porous anodic alumina are compared with regard to homogeneous and partial filling of pores and filling of pores by nanoparticles. Electrochemical and chemical deposition techniques such as successive ion layer adsorption reaction are used. Metals and metal sulfides have been deposited into pores of about 10 µm length and 10-50 nm diameter. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), optical and photovoltage spectroscopy confirms successful synthesis of nanocrystals with desired properties.

A surface morphology in the binary metal systems treated by compression plasma flow is studied. Formation of cellular structure is shown. The size of the cells is 500-1000 nm depending on the particular system. The mechanism of low-dimensional cellular structure formation is described on the basis of the concentration overcooling model.

The structure of Ni/a-C:H films was investigated as a function of carbon content. Ni₃C crystallites of 5-20 nm were formed when concentration of CH₄ was in the range of 15-30 %. The matrix in the films with atomic ratio C/(Ni+C)>47 % has appeared to be hydrogenated amorphous carbon with the ratio sp²/sp³=1/5 and the size of carbon clusters of 1 nm.

We present structure and surface morphology investigations of nanosized coatings on silicon fabricated by compression plasma flows studied by an atomic force microscopy and scanning electron microscopy. It was found that the exposure of semiconductor materials to compression plasma flows generated in the magnetoplasma compressor simultaneously with electrical explosion of metal wires resulted in deposition of a finely structured single-layer coating composed of metal-based spherical particles of 100-200 nm.

An original instrument intended to integrate the advantages of scanning probe microscopy, near and far field optical microscopy is presented. The device is supposed to be a powerful tool for high resolution analysis in different fields such as material sciences (optical and optoelectronic, magnetic, semi- and superconducting materials), polymers and biological sciences (structural biology, molecular and cell biology, microbiology, etc.).

The paper reports about the possibility of managing the structure and properties of multilayer protein films by varying the nature of polymeric surfaces. Collagen, fibronectin, and human serum albumin have been chosen as model systems. The kinetics of adsorption was studied in various protein solutions by means of in situ quartz crystal microbalance (QCM) with dissipation monitoring on poly(methylmetacrylate), poly(hydroxymethylsilane), ε-poly(caprolactone) and polyelectrolyte films. The structure and the mechanical properties of the adsorbed protein layers were studied by atomic force microscopy (AFM). The results allowed us to identify different adsorption processes as a function of the surface wettability. As a special case, the mechanism of collagen adsorption and reorganization on different polymer surfaces has been investigated.

A possibility to use mono- and multilayer Langmuir-Blodgett films of 2,4-heneicosanedione as an “ink” for microcontact printing for silicon surface patterning has been shown.

We consider different approaches to implementation of porous silicon as a biomedical material employing concepts of formal creative thinking. The performed analysis shows wide possibilities of porous silicon application in the formation of different nanosize composite materials and structures for orthopaedic implants.

High electron mobility transistors (HEMT) with a 2-dimensional electron gas (2DEG) channel formed by an AlGaN/GaN heterointerface were fabricated from MOCVD-grown heterostructures on Si (111) and sapphire substrates. The electrical characterization including C-V profiling and DC as well as RF measurements evidenced good transistor properties of all structures under study. Typically, comparable structures on Si (111) show output characteristics up to 50 V in drain-source voltage and cut-off frequencies of f_t/ f_max=7 GHz /12 GHz. Optical characterization by means of PL and reflection spectroscopy demonstrated the high quality of the samples and allowed to estimate the values of strain in the AlGaN/GaN heterointerface region. The presence of this heterointerface leads to a modification of the reflection spectra compared to an uncapped GaN layer surface, which may be a future basis for understanding and estimating the interface parameters such as surface charge density or the field distribution in the vicinity of the 2DEG channel.

During the last years, a growing interest in the creation of micro- and nanoelectronic devices by use of the Swift Heavy Ion (SHI) track technology has been observed. First prototypes of transformers and capacitors for nanotechnology applications were created in this way on the base of polyimide (PI) foil with etched ion tracks. Complex testing of the obtained devices has shown their good operational ability for the use in various industrial applications.

Hole transport through strained Si/Si_1-xGe_x/Si double barriers has been investigated and simulated accounting for processes of resonant tunneling and thermally activated charge transfer. Two resonant peaks were found in the current-voltage characteristics of the stack resulting from the contribution of heavy and light holes transfer components. The strain induced critical thickness of the constitutive layers of the structure allows a design for which a peak-to-valley ratio up to ~1300 is calculated for the heavy hole current component. Due to the relatively high potential barrier height, the contribution of the thermally activated transfer is found to be negligible.

The current-voltage characteristics of CaF₂ films are presented. This paper report the negative differential resistance effect caused by dynamic effets temporal. This observation is validated by a simulation from an equivalent circuit made up of resistances and capacities.

The structure of opal matrices (ordered SiO₂ nanospheres) and multilayer structures based on opal matrices (opal matrix/diamond-like carbon, opal matrix/nickel/diamond-like carbon and other) are considered. Cold cathodes formed on the basis of layer structures and regular cubic SiO₂ packing and diamond-like materials are studied.

Amplitude and phase spectra of light reflection from distributed Bragg reflectors and Fabry-Perot microcavities based on α-Si:H/α-SiO_x:H thin films have been studied with an ellipsometric technique. The TM-TE phase shift for complex amplitude reflection coefficients is measured within photonic band gaps of the periodic structures fabricated. The phase spectrum exhibits predominantly monotonic, close-to-linear frequency behavior except for the photonic band gap edge regions and narrow spectral ranges including the microcavity eigenmode singularities. A method exploiting the analysis of amplitude-phase reflectance spectra is proposed for fine structural characterization of multilayer microcavity systems.

A comparison of the formfactors calculated using envelope wave functions with the formfactors for the ideal quantum wire structure was done. These formfactors have the significant difference. Moreover, the gate voltage influences the values of formfactors.

Carbon nanotubes (CNT) are being intensively developed for novel electronics. Electron cooling by superconductor-insulator-nanotube (SIN) tunnel junctions could be extremely effective due to the small volume of the CNT. A novel concept of a cold-electron bolometer with a CNT as an absorber should demonstrate record sensitivity due to the very low temperature that is predicted to be reached in the CNT (less than the phonon temperature). Objectives of this work are to demonstrate effective electron cooling in superconducting nanostructures comprising of carbon nanotubes and to develop a supersensitive cold-electron bolometer based on a cooled carbon nanotube as absorber.

A nanoelectromechanical memory device including a carbon-nanotube-bridge was investigated by atomistic simulations based on empirical potentials. In the device, the electrical-induced potential energy is changed to the mechanical energy and the van der Waals interactions between the bridge and the oxide are very important. As the distance between the bridge and the oxide decreases and the van der Waals interaction energy increases, the pull-in bias of the carbon-nanotube-bridge decreases and the nonvolatility of the nanoelectromechanical memory device increases while the pull-out voltages increases.

A new process for fabrication of horizontally oriented carbon nanotubes is presented. Diode and triode I-V characteristics are investigated. High reproducibility of the electrical parameters at large surface area is demonstrated. The developed technology of planar vacuum emission device fabrication opens wide perspectives of their application in micro- and nanoelectronics.

Waveguiding properties of coupled nanopillar periodic waveguides with out-of-phase coupling are studied. Two regimes, namely, weak and strong coupling, are realized by arranging dielectric nanopillars in vertices of triangular lattice with Γ-J and Γ-X lattice orientations, respectively. Based on unique dispersion and transmission properties of the coupled periodic waveguides, efficient photonic components are proposed.

Optical anisotropy introduced into a constituent material of a binary multilayer nanostructure with sharp transmission peaks is shown to cause resonance transmission peak splitting. Introducing optical gyrotropy along with anisotropy, we show that the output polarization for split components can be sufficiently modified, while the split component frequencies are unchanged. Based on this, the design of a frequency-selective polarizer with arbitrary output polarization is proposed.

Porous anodic films were grown by a multi-step anodization on sputtered aluminum and subjected to open-circuit dissolution to modify the pores and improve the film structure. The anodic films were used as a support material for magnetron sputtering-deposition of thin layers of WO₃ with gas-sensing properties. Uniform continuous layers of WO₃ of 250-700 nm thicknesses were deposited in the alumina pores of diameters of 60-160 nm. Test sensors showed the response to ammonia in the temperature interval of 250-300 °C.

The possibility to improve sensitivity of a spectral-absorption sensor to ammonia vapors of low (less than 1 vol.%) concentrations using the methyl red azodye as an indicator in a sensing element on the basis of nanoporous glass is shown. The possible mechanism of this improvement and spectral features of the nanocomposite material are discussed.

AUTHOR INDEX.