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The possibility of modifying the photoluminescence properties of porous silicon by irradiation with low doses of γ photons from a 226Ra radioisotope source and bremsstrahlung is demonstrated. The position of the longest photoluminescence wavelength tends to shift to the short-wavelength region of the spectrum. The emission efficiency increases upon irradiation of both the substrate and the layer formed.

The paper presents the method of tunneling microscopy study of mass transfer in the structure containing nanometer layer AgI. The possibility of using of interface Ag-AgI-insulator-metal as a resistive switching memory with charge ∼5 pC and multiplicity of resistance ∼20 is shown.

Electrical and photoelectric properties of porous silicon with introduced silver nanoparticles have been studied. It is shown that in the “dark–light–dark” operation mode, an abrupt jump of the dark current is observed upon illumination (with light spectrally close to sunlight), which is three to five times the initial dark current and the photocurrent. The voltages at which these abrupt changes in current are observed correspond to the range of existence of traps formed when the starting mesoporous silicon is obtained. It was found that the increased value of the dark current exhibits a long-term memory effect. The “current jump” can be attributed to the maximum capture of the generated photocarriers by traps, followed by their release in an electric field after the illumination.

The photoelectric and photovoltaic properties of structures based on mesoporous silicon passivated with iron (SiMP:Fe) are studied. It is shown that these properties ambiguously depend on the iron concentration. In the case of a sample with space-charge-limited currents (SCLCs), the charge-transport mechanism in the Al-SiMP:Fe-p-Si-Al heterostructure changes under illumination from the SCLC type to the barrier type. Passivation with 0.1–0.2 at % iron stabilizes not only the electrical, but also the photoelectric and photovoltaic properties of the structures. A further increase in the Fe concentration gives rise to new traps caused by the appearance of iron and silicon oxides, which leads to instability of the properties. The structures exhibit high sensitivity under low-level illumination. The open-circuit voltage is 16 mV under AM-1 irradiation (∼2 mW/cm2).

The possibilities of modifying the IR spectra of porous silicon under irradiation by low doses of gamma — quanta of radioisotope source of 226Ra and bremsstrahlung radiation are investigated.

The electrical and photoelectric properties of nanostructures with porous silicon layers obtained by electroless etching of silicon have been investigated. It is found that the photoelectric and photovoltaic properties of these structures depend on their morphology and are determined by not only the properties of the modified layer, but also the presence of possible barriers in the layered porous silicon. The ratio of the photoconductivity to the dark conductivity reached 102−5 × 102. An open-circuit voltage V oc was detected that amounted to ∼250 mV at an incident light power close to AM-1 (∼100 mW/cm2). In this case, the density of short-circuit current I sc was about 20 μA/cm2.

The possibility of multiparametric determination of properties of structures from the data on the dependence of reflectances Rp and Rs for polarized radiation and ratio Rp/Rs on the angle of incidence θ and from the angular dependence 1/Rp(ΔR/Δθ) is investigated. The results of natural and computer experiments revealed a high sensitivity of the angular dependence Rp(θ) of the reflectance to the values of optical constants and thickness of layered structures. Quantitative results of multiparametric measurements are verified by the independent method of spectral ellipsometry. The possibility of multiparametric determination of the properties and thickness of nanometer dielectric, metallic, and semiconducting layers on various substrates and the properties of substrates in such structures is established.

The results of numerical simulation of a nanodimensional film-transition layer-absorbing substrate structure are presented. It is found that the transition layer affects the accuracy of determining the refractive index and thickness of the nanodimensional coating. It is shown that the introduction of the effective values of the refractive index and absorption coefficient of the substrate improves the accuracy of ellipsometric measurements of the nanodimensional film parameters. Physical (full-scale) and numerical experiments demonstrate that, when the thickness and refractive index of a nanodimensional film on a substrate with an unknown transition layer comparable in thickness with the film are measured, it is appropriate to replace the substrate-transition layer structure by a substrate with effective optical parameters. It is found that a change in the thickness of the transition layer does not noticeably affect the accuracy of determining the thickness and refractive index of the film deposited when the effective values of the refractive index and absorption coefficient of the substrate are used.

A noncontact method for the express-testing of the relative deformation of lattice parameter (Δa/a ) of semiinsulating GaAs has been developed. This method is based on measuring the reflected radiation in band-to-band regions L3v - L1c and X5v - X3c. The suggested method ensures a resolution of 4 × 10-5 in determining (Δa/a ) and has a measurement accuracy of about 0.5%.

In situ measurement of the formation process of low-dimensional porous silicon (PS) structures was developed. The measurements are based on the analysis of polyharmonic time dependence of the reflected radiation. The results show high sensitivity to H 2 S in PS based structures with catalytic (Pd, Ni) and ohmic (Al) electrodes. In the best samples the appearance of three molecules H 2 S on 10 9 molecules N 2 increased the electrical current value by a factor of 2–3. The structures selectively measure H 2 S concentration from 0.02 to 1000 ppm. It was found that unusually high reversible and nonreversible optical properties change because of the influence of gas solvents and alcohol. The exposure of PS layers to ethyalcohol vapor changes the color of PS from bright blue to crimson and the refraction coefficient in the IR region changes up to 0.06.

In the present study a novel approach to caries management based on the application of nanoparticles of different nature to increase the mineral phase of demineralized dentin has been developed. Silver nanoparticles have been tested as a material for dentine matrix infiltration. Research findings clearly show that collagen fibers of demineralized dentine could be considered as a scaffold for mineral component delivery and the place where mineral growth can occur. Keywords : dental research, demineralized dentine, dentin collagen fibers, nanotechnologies, silver nanoparticles, nanoparticle infiltration, scanning electron microscopy 1. INTRODUCTION The first stage of caries developing is characterized by hard tooth tissue demineralization. A series of methods are being developed to manage the caries process; one of the most popular is the application of remineralizing therapy along with demineralized dentine collagen matrix protection. In clinical practice a variety of strategies of dentine and enamel remineralization based on the application of bioactive glasses, calcium hydroxiapatite, fluoride delivering materials, artificial saliva and others are in common use

Memristor structures based on tunnel-thin organic dielectric and porous silicon layers are investigated.

In this study the methodology of biological sample preparation for dental research using SEM/EDX has been elaborated. (1)The original cutting equipment supplied with 3D user-controlled sample fixation and an adjustable cooling system has been designed and evaluated. (2) A new approach to the root dentine drying procedure has been developed to preserve structure peculiarities of root dentine. (3) A novel adhesive system with embedded X-Ray nanoparticulate markers has been designed. (4)The technique allowing for visualization of bonding resins, interfaces and intermediate layers between tooth hard tissues and restorative materials of endodontically treated teeth using the X-ray nano-particulate markers has been developed and approved. These methods and approaches were used to compare the objective depth of penetration of adhesive systems of different generations in root dentine. It has been shown that the depth of penetration in dentine is less for adhesive systems of generation VI in comparison with bonding resins of generation V, which is in agreement with theoretical evidence. The depth of penetration depends on the correlation between the direction of dentinal tubules, bonding resin delivery and gravity.

The possibilities of creating sensors on the basis of silicon structures with classical and quantum-dimensional effects have been researched theoretically and experimentally. The technology of forming qnantuln-well and wire structures of porous and amorphous silicon and their modifications by multiparameter monitoring in situ has been studied. H 2 S sensor samples, developed on this basis, have a high sensitivity (on the level 10-20 ppb), low operating voltage (1-1.5 V), low power consumption (not more than 10 -8 -10 -6 W) and relative selectivity to hydrocarbons, CO and CO 2 . The most sensitive to H 2 S ate structures having p = 0.03 Ω cm, oxidized porous silicon layer thicknesses of 6-10 μcm, porosity of 0.75-0.8 and Pd layer thicknesses of 50-60 nm. The obtained results verify the principle possibilities in solving all growing contradictions between information processing and its reception by using low-dimensional structures.

In sectional operation the basic attention is given to clearing up of dependences between an acting voltage and change of properties of an aggregate in field before failure of system, in which the realization both continuous, and jump changes of properties is possible. This field is of interest for those applications in an electronics, in which the hysteresis of properties and storage of action is not necessary.

The possibilities of micro- and nanoelectromechanical systems analogs of structures with PCMS have been researchers, theoretically. The offered structure is considered, in which the series switching of devices from one state in another is implemented and the self-distribution of the switched state along structure and its transition to a new state (principle of a domino) is carried out. On the base of the solution of differential equations linking cantilever bias (sag) to its design parameters and an affixed voltage it was established, that in meshes with d>100-150 nm to the defining speaker of meshes and processes of failure (the switching) are forces of Coulomb and elasticity, the Casimir force become essential at d

We discuss the possibility of determining the electrophysical properties of semiconducting materials based on the determination of their optical constants by the method of broken total internal reflection. As the material for the total-internal-reflection prism it is proposed to use the experimental material, but with a much lower carrier concentration, The possibilities of the proposed method are demonstrated using as an example high-resistance silicon for the TIR prism and the experimental sample of n-type silicon.

A nondestructive method of determining the parameters of epitaxial film systems is proposed based on a variational method of computing the coefficients of reflection and transmission of an electromagnetic wave in lamellarly inhomogeneous semiconductor structures. Structures of the type low-alloy film-transition layer-high-alloy substrate are considered with various prescriptions for varying the concentration of the alloying additives in the transition layer near the plasma resonance of the charge carriers in the substrate. Preliminary experimental investigations of the epitaxial N-N+ structures of silicon are in satisfactory agreement with computed data. The proposed method makes it possible to determine the thickness of the low-alloy layer and of the transition layer separately on the basis of the spectral dependence of the reflected radiation.

The reflection coefficient R and the phase angleϕ of the reflected electromagnetic wave are calculated with an account of various scattering mechanisms (scattering by ionized impurity and by optical phonons) for wavelengths in the 2-mm range at room temperature. Simplified semiclassical equations for the complex reflection coefficient R* are shown to be valid. The equations are used to calculate R and ϕ for n-type GaAs as functions of the dimensionless frequencies y = ω/ωp and ωpτ. The experimental values of R and ϕ for n-type GaAs single crystals at 2.2 mm agree with the theoretical values, within the experimental error. The concentrations and mobilities determined from the experimental data agree well with the results of Hall measurements.

Bistability of the optical properties with respect to radiation power was observed for vanadium dioxide films. An analysis was made of nonlinear temperature switching waves and of waves involving switching of the optical properties associated with this bistability. A switching wave was observed experimentally.