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Experimental data have been obtained for the relaxation rates of population, orientation, and alignment of the 174Yb(6s6p)3P1 level due to collisions of 174Yb atoms with atoms of noble gases.

The nonmonotonic kinetics of a collision-induced photon echo has been investigated for a number of buffer atoms. The collision-induced photon echo was generated at the 174Yb (6s2) 1S0 ↔ (6s6p) 3P1 (0 ↔ 1) transition by a pair of linearly and mutually orthogonally polarized resonant radiation pulses in ytterbium vapor and its mixtures with He, Ne, Ar, Kr, and Xe. The kinetics of the conventional photon echo generated by pulses with identical linear polarizations was recorded in the same mixtures. The derived decay rate constants for both types of echo are equal to within the measurement errors. For the collisions of 174Yb atoms between themselves and with other ytterbium isotopes in a natural mixture of isotopes, an upper limit for the anisotropy parameter has been estimated, 0.22 ± 0.07 of the photon echo signal decay rate.

A broadband near-IR photodetector based on a large-area G12180-250A InGaAs photodiode (Hamamatsu) with a 5-mm-diameter photosensitive area was developed and tested. It is designed for detecting the IR luminescence of singlet oxygen. A circuit for signal amplification is assembled on the basis of broadband low-noise operational amplifiers with the subsequent filtering of a signal with an adjustable passband f varied from 15 to 600 kHz, thus allowing one to obtain a time resolution of better than 1 µs, a sensitivity level of 107–109 V/W, and a noise equivalent power NEP [W/Hz1/2] ≈ 1.4 × 10–14λ–1[µm] f [kHz] in a frequency band of 15–600 kHz.

For the first time, a complete set of decay parameters, due to collisions of 174Yb atoms with noble gas atoms and with ytterbium atoms, was experimentally found for the 174Yb (6s6p) 3P1 level. The method of stimulated photon echo with special angles between the polarization vectors of light pulses forming an echo at the 174Yb (6s2) 1S0—(6s6p) 3P1 transition (type 0 ↔ 1 ) is used. For each buffer gas of He, Ne, Ar, Kr, Xe, and Yb, the decay rate constants of population, orientation and alignment for the collision destruction of the 3P1 level of 174Yb atoms are determined. All the decay rates demonstrated their linear increase with a buffer gas pressure, and the corresponding relaxation constants are determined. Each of the indicated relaxation constants, as well as the difference between the alignment and orientation relaxation constants, increases with the increasing buffer gas mass.

The phase and elemental compositions of GeSi heterostructures deposited on non-refractory substrates are analyzed by using a non-destructive express technique, i.e., the Raman spectroscopy. It is shown that application of pulsed laser annealing allows one to vary the elemental composition and size of nanocrystals formed from solid alloys of germanium and silicon.

Silicon nanocrystals are formed in the i layers of p–i–n structures based on a-Si:H using pulsed laser annealing. An excimer XeCl laser with a wavelength of 308 nm and a pulse duration of 15 ns is used. The laser fluence is varied from 100 (below the melting threshold) to 250 mJ/cm2 (above the threshold). The nanocrystal sizes are estimated by analyzing Raman spectra using the phonon confinement model. The average is from 2.5 to 3.5 nm, depending on the laser-annealing parameters. Current–voltage measurements show that the fabricated p–i–n structures possess diode characteristics. An electroluminescence signal in the infrared (IR) range is detected for the p–i–n structures with Si nanocrystals; the peak position (0.9–1 eV) varies with the laser-annealing parameters. Radiative transitions are presumably related to the nanocrystal–amorphous-matrix interface states. The proposed approach can be used to produce light-emitting diodes on non-refractory substrates.

Raman scattering spectroscopy is powerful, express and non-destructive method for control of phase composition of different materials. To determine the crystalline part, one should know the ratio of Raman cross sections of crystalline to amorphous phases. In this Letter we report on accurate comparative measurements of the Raman scattering from monocrystalline and nanocrystalline Ge, as well as from amorphous Ge films. Being accompanied by the respective optical transmittance/reflectance measurements, these data allowed us to estimate the integrated Raman scattering cross section ratios of monocrystalline and nanocrystalline Ge to amorphous Ge, for the first time. For monocrystalline Ge the obtained ratio is equal to 4, while for nanocrystalline Ge this ratio decreased monotonously with a decrease of the nanocrystal sizes. Some physical reasons of the experimentally observed dependence are proposed.

Silicon nanocrystals and germanium nanolayers and nanocrystals were created into i-layers of p–i–n structures based on thin hydrogenated amorphous silicon films. The nanocrystals were formed using pulsed laser annealing with an excimer XeCl laser generating pulses with the wavelength of 308 nm and the duration of 15 ns. The laser fluence was varied from 100 (that is below the melting threshold) to 250 mJ/cm2 (above the threshold). The laser treatment allowed the formation of the nanoscrystals with the average size from 2 to 5 nm, depending on the laser-annealing parameters. The size of nanocrystals (in Si and Ge layers) and their Si-Ge composition (in GeSi alloy structures) was estimated through Raman spectra analysis. The structural parameters of Si, Ge and GeSi nanocrystals were also studied using electron microscopy and atomic force microscopy. Current–voltage measurements showed that the p–i–n structures exhibit diode characteristics. The diodes with Si nanocrystals produced the electroluminescence peak in the infrared range (0.9–1.0 eV), which spectral position was dependent on the laser annealing conditions. It was suggested that radiative transitions are related to the nanocrystal/amorphous silicon matrix interface states. The proposed approach can be used for producing of solar cells or light-emitting diodes on non-refractory substrates.

Photon echo generated at the inter-combination transition (6s2) 1S0 − (6s6p) 3P1 of 174Yb was investigated for pure ytterbium vapor and for its mixtures with atomic buffers. In pure ytterbium vapor, the polarization of photon echoes at this 0–1 transition coincides with the polarization of the second exciting pulse for all combinations of linear and circular polarizations of exciting radiation pulses. Photon echo does not appear either for linear orthogonal or for opposite circular polarizations of exciting pulses in pure ytterbium. In mixtures of ytterbium with atomic buffers (Kr, Xe), collision induced photon echo arises only for exciting pulses of linear orthogonal polarizations, its power is essentially less than that of the ordinary echo generated by pulses with parallel polarizations in the same mixture. Polarization of collision induced echo is linear, and it coincides with polarization of the first exciting pulse. Experimental results agree with calculations, and they confirm that the collision induced photon echo at this transition arises exclusively due to anisotropy of depolarizing collisions.

A great variety of coherent transient processes in atomic and molecular gases is investigated. The degeneracy with respect to magnetic sublevels, which is typical of working levels of atomic and molecular transitions in gases, leads to new phenomena. In particular, the non-Faraday rotation of the coherent-response polarization vector at the 0 ↔ 1 transition is investigated in the presence of the longitudinal magnetic field in the 174Yb vapor for both photon echo and stimulated photon echo. A specific relaxation channel that involves the depolarizing collisions emerges in a gas due to the degeneracy of working levels. Such collisions are especially important for atoms and are also observed in molecules. The anisotropy of the depolarizing collisions leads to a new phenomenon of the collision photon echo, which is experimentally demonstrated for the 0 ↔ 1 transition in the 174Yb mixtures with atomic buffers. The velocity-dependent relaxation rates are observed for various coherent phenomena in molecular gases. The coherent control of a few coherent transient processes is implemented.

Polarization properties of photon echo generated at the inter-combination transition (6s2) 1S0 ↔ (6s6p) 3P1 of 174Yb (transition of type 0 ↔ 1) are for the first time investigated experimentally for a complete set of polarizations of two exciting pulses of resonant radiation (linear-linear, circular-linear, linear-circular, and circular-circular) in a pure ytterbium vapor. In all cases the photon echo polarization coincides with polarization of the second exciting pulse. Photon echo in a pure gas does not appear neither for exciting pulses of mutually orthogonal linear polarizations, nor for the pulses of opposite circular polarizations. Experimental results are in agreement with theoretical predictions.

The photon echo method was used to detect an increase in the relaxation rate in the vibrational-rotational transition of fluoromethane in 13CH3F gas and a 13CH3F-argon mixture upon an increase in the velocity of active particles. For a photon echo in the 0–1 transition in a Yb + Xe mixture, the dependence of the relaxation parameters on the direction of the translational velocity of Yb leads to qualitative changes and a collision photon echo arises.

The shortening of the absorption recovery time by a factor of more than 50 is observed for the semiconductor nanostructure consisting of ten GaAs/InxGa1-xAs/GaAs quantum wells irradiated with the nanosecond pulses of the XeCl laser.A possible reason for such a significant variation in the optical properties lies in the generation of point defects,which are responsible for recombination of charge carriers.The result can be employed in the UV photomodification of optical properties of semiconductor nanostructures.

The effect of translational velocity of active atoms and molecules on the properties of photon echo is investigated using the technique of coherent transient processes. A variation in the photon-echo decay with a frequency detuning of the excitation radiation relative to the center of the vibrational-rotational transition 0 ↔ 1 ν3 R(4, 3) is observed in a mixture of 13CH3F with atomic buffers. The results are interpreted using the dependence of the echo decay rate on the magnitude of the translational velocity of active particles. The dependence of the relaxation matrix on the direction of the velocity of active atoms results in a new phenomenon of the collision-induced echo, which is investigated at the transition 0 ↔ 1 174Yb in mixtures with atomic buffers.

The polarization properties of the photon echo generated by two linearly polarized pulses of resonant radiation at the (6s6p)3 P 1 ↔ (6s 2)1 S 0 transition of 174Yb are investigated. A complicated polarization behavior of the photon echo versus an angle between the polarization vectors of the excitation pulses is revealed in a mixture of ytterbium vapor with inert gas. For the angles ranging from 0° to 75°, a conventional echo with its linear polarization coinciding with the second excitation pulse dominates and the echo amplitude decreases with an increasing angle. For the angles ranging from 75° to 89°, the photon echo is elliptically polarized. Finally, for an angle of 90°, the conventional echo disappears and the collision echo becomes linearly polarized along the first excitation pulse.

Isotropic depolarizing collisions are studied using a stimulated photon echo with a specific polarization of the excitation radiation pulses in a mixture of ytterbium with krypton for the J = 1 ⇄ J = 0 transition of 174Yb. The difference between the relaxation rates of orientation and alignment γb(2) − γb(1) of the 3P1(6s6p) 174Yb level is measured as a function of the krypton pressure. The collision photon echo at the J = 1 ⇄ J = 0 transition induced by the anisotropic relaxation is studied for the Yb + Xe mixture. The power of the collision echo increases from zero with the addition of a buffer gas to ytterbium, reaches an optimal level, and decreases with an increase in the buffer gas pressure. The polarization of this collision-induced echo differs from the polarization of the conventional echo. The experimental results are in qualitative agreement with theoretical predictions.

Collision induced photon echo generated at the inter-combination transition (6s6p) 3P1 ↔ (6s2) 1S0 of 174Yb in the mixture Yb+Xe is investigated. Collision echo is generated by two unidirectional pulses of resonant radiation with linear and mutually orthogonal polarizations. The collision induced echo appears exclusively due to Yb collisions with buffer, and its polarization coincides with polarization of the first exciting pulse. Experimental results are in qualitative agreement with theoretical predictions for anisotropic depolarizing collisions.

Thin (90 nm) a-Si:H films on Corning 7059 glass substrates have been crystallized by 120 fs pulses of Ti:sapphire and nanosecond pulse XeCl and KrF excimer lasers. Initial films were deposited using low-temperature plasma enhanced deposition technique. The structural properties of the films were characterized using the spectroscopy of Raman scattering, excited by the argon laser (line 514.5 nm) and using electron microscopy. For the femtosecond pulse treatments the ablation threshold was found to be some more than 65 mJ/cm2. When pulse energy density was lower than ~30 mJ/cm2 no structural changes were observed. In optimal regimes the films were found to be fully crystallized with needle grain structure, according to the Raman scattering and electron microscopy data. Estimates show the pulse energy density was lower than the Si melting threshold, so non-thermal “explosive” impacts may play some role. The main result in nanosecond XeCl and KrF laser pulse crystallization is the narrower window between beginning of crystallization and ablation for KrF laser (wavelength 248 nm) than for the XeCl laser (wavelength 308 nm). So, the possibility of the femtosecond and nanosecond laser pulses to crystallize a-Si films on non refractory glass substrates was shown. The results obtained are of great importance for manufacturing of polycrystalline silicon layers on non-refractory large-scale substrates for giant microelectronics.

Characterisation of three-layer dielectric embedded into MDS-structure (Metal- Dielectric-Silicon) was provided in the dark and under light illumination. In the dark, increasing of differential capacitance, simultaneously, with variation of differential conductivity of MDSstructures was detected. In the light strong changing of capacitance part of impedance was firstly observed, demonstrating decreasing almost to zero values and restoring up to maximal values in narrow bang of voltage applied. Variation of capacitance exceeds significantly so called dielectric layer capacitance, what interpreted as carriers exchanging between substrate and electronic states in SiNx probably due to three-layered kind of its nature.

The possibility for echo signal switching-off and the switching of echo polarization between the ±45° positions is demonstrated for the photon echo (PE) and stimulated photon echo (SPE) generated in Yb vapor at the (6s6p) 3 P1 - (6s 2 1S 0 transition by two pulses of the resonant linearly polarized radiation at appropriate experimental parameters in the weak magnetic field limit. The experimental data are in qualitative agreement with the theoretical analysis and the calculations made for the 1 ↔0 transition. The strong magnetic field limit leads to unpolarized PE and SPE signals generated by linearly polarized radiation pulses. The possibility of the generation of a long-lived echo in ytterbium vapor due to the magnetic field induced mixing of the upper working level with the metastable level is discussed. The results can be employed for the optical data storage and processing.

First proposal is made to measure the ratio of stimulated photon echo power corresponding to two different mutual orientations of exciting pulses polarizations as a function of the buffer gas pressure to extract the spectroscopic information concerning the relaxation rates difference of orientation and alignment from these measurements. The absolute value of the difference between relaxation characteristics |γb (1)-γb (2)| corresponding to orientation and alignment of 3P1 (6s6p) level of 174Yb due to it's collisions with krypton atoms is measured. The fact of the difference between orientation and alignment relaxation rates is reliably stated.

Polarization of the stimulated photon echo (SPE) at the 0 ↔ 1 transition in ytterbium vapors in the presence of a longitudinal magnetic field of 0–40 G is experimentally and theoretically studied. The SPE is generated using three light pulses with identical linear polarizations, so that the SPE polarization is the same at zero magnetic field. In the presence of a weak magnetic field, the SPE polarization vector rotates around the magnetic field vector and the depolarization of the SPE signal takes place. Each of the SPE polarization components exhibits biharmonic oscillations depending on the magnetic field. In the presence of a strong magnetic field, these oscillations vanish and the SPE becomes depolarized. The experimental data are in qualitative agreement with the results of the numerical calculations performed with the method of the evolution operator for the finite-duration excitation pulses. The application of the results for the processing of optical data is discussed.

The laser assisted formation of silicon nanocrystals in SiNx films deposited on quartz and silicon substrates is studied. The Raman spectroscopy revealed creation of the Si cluster and crystallite after excimer laser treatments. Photoluminescence signal from the samples was detected at room temperatures. I-V and C-V measurements were carried out to examine carries transfer through dielectrics film as well as recharging of electronics states.

Two fractions of membrane fragments—the pellets precipitated at 1300 and 20000 g (fractions G1.3 and G20, respectively)—were isolated from pea (Pisum sativum L.) chloroplasts after solubilization with digitonin. These fragments assigned to grana displayed the following differences: (1) in spectra of low-temperature fluorescence, the ratio of short-wave and long-wave band intensities, as well as integrated intensity of the whole spectrum, were higher for G1.3 than for G20 fraction; (2) in excitation spectra of long-wave fluorescence, the ratio of peaks at 650 and 680 nm and integrated intensity of the spectrum were higher for G1.3 than for G20 fraction; and (3) the shapes of fluorescence excitation spectra differed for G1.3 and G20. These results indicate that the two fractions examined differed in proportion of photosystem I and photosystem II complexes, as well as in organization of these complexes. The size of light-harvesting antenna was larger in PSI complexes of G1.3 fraction, owing, in particular, to a higher content of chlorophyll a/b-protein complexes in this fraction. After repeated digitonin fragmentation of G1.3 and G20 preparations, more than 80% of G1.3 fraction was decomposed into lighter fragments, whereas G20 fraction was resistant to fragmentation (it lost about 10% of its material). Analysis of the data suggests the presence of two structurally different types of thylakoids in grana. The yield of G20 fraction (about 20%) is comparable to the ratio between the number of intergranal thylakoids, connected to granum in pea chloroplasts, and the total number of thylakoids in this granum. Based on these data, we assume that G20 fraction represent the fragments of intergranal thylakoids that extend into the granum.

Shape correlation and magnetic field control of stimulated photon echo (SPE) are investigated as basic properties useful for optical data storage and treatment. The SPE polarization was investigated in ytterbium vapour at the intercombination transition (6s6p) 3P1 → (6s2) 1S0 for the first time in a wide range of longitudinal magnetic field strength. SPE was generated by three resonant laser pulses of identical linear polarization and wave vectors directed symmetrically at small angles to the axis of cylindric vapour cell. SPE polarization is close to linear one in zero magnetic field. As magnetic field increases, the SPE polarization acquires ellipticity with the ellipse axis rotated around magnetic field vector. Components of SPE polarization show oscillations versus magnetic field with higher contrast of the oscillations in the weak field.

Two fractions of the light fragments enriched in the photosystem I (PSI) complexes were obtained from pea (Pisum sativum L.) thylakoids by digitonin treatment and subsequent differential centrifugation. The ratio of chlorophyll a to chlorophyll b, chlorophyll/P700 spectra of low-temperature fluorescence, and excitation spectra of long-wave fluorescence were measured. These characteristics were shown to be different due to variation in the size and composition of the light-harvesting antenna of PSI complexes present in the particles obtained. The larger antenna size of one of the fractions was related to the incorporation of the pool of light-harvesting complex II (LHCII). A comparison with the data available allowed us to identify these particles as fragments of intergranal thylakoids and end membranes of granal thylakoids. The suggestion that an increase in the PSI light-harvesting antenna in intergranal thylakoids is related to the attachment of phosphorylated LHCII is discussed.

Detailed experimental analysis of photon echo polarization in a longitudinal magnetic field is performed for the first time at the simplest quantum transition J = 1 ↔ J = 0 for which the non-Faraday rotation of photon echo polarization plane was predicted. The echo was generated at the intercombination transition (6s6p) 3P1 → (6s2) 1S0 of 174Yb by two resonant laser pulses of linear (parallel or mutually orthogonal) polarization, and the angled echo optical scheme was applied for the detection. At the magnetic field strength ℬ ⩽ 5 G the photon echo has polarization very close to linear one; its polarization plane rotates around magnetic field vector, and photon echo polarization components and integral echo power oscillate versus ℬ from its maximum value to zero, in agreement with theory. At a stronger magnetic field ℬ ∼ 40 G photon echo power oscillations disappear, no preferable orientation of polarization vector is observed; the fluctuations of exciting radiation spectrum are supposed to be responsible for this "non-polarized" echo.

Grana-core and grana-margin fragments were obtained from pea (Pisum sativum L.) thylakoids, and both fractions contained photosystem I (PSI) complexes. The yield of these fractions exhibited variations for the plants grown during various periods of the summer season. Low-temperature fluorescence spectra, excitation spectra of long-wave fluorescence, and P700 kinetic characteristics were recorded for these fractions. PSI complexes in central granal regions were associated with PSII and the light-harvesting complexes of PSII, which followed from the excitation spectra of long-wave fluorescence and the kinetic characteristics of P700 light oxidation and dark reduction. The characteristics of the margin regions were changed depending on the fraction yield. If the yield was low, marginal fragments contained mainly PSI complexes. When the yield increased, PSI associates with PSII appeared. A spatial distribution and state of PSI complexes in granal thylakoids are discussed as related to the size and composition of the light-harvesting antenna.

In the present study, the photoionization spectrum of the SO2 molecule in a molecular beam was studied in detail using radiation of the ArF (λ = 193 nm) and XeCl (λ = 308 nm) excimer lasers. No signals corresponding to the Van der Waals complexes or clusters of the SO2 could be detected. The profile of the SO + and S + peaks at 193 nm could be fitted by superposition of two Gaussian functions, while at 308 nm a single Gaussian was sufficient. Power dependencies studied show that photoionization is a multiphotonic process in both cases. © 2002 Elsevier Science B.V. All rights reserved.

Using Raman scattering, it was ascertained that silicon nanocrystals with sizes exceeding 2 nm are formed in amorphous silicon films exposed to nanosecond ultraviolet laser radiation with energy densities ranging from 75 to 150 mJ/cm2; it is shown that these nanocrystals have sizes no smaller than 2 nm and have preferred (100) orientation along the normal to the film surface. In a system of mutually oriented Si nanocrystals, anisotropic behavior of the Raman scattering intensity was experimentally detected in various polarization configurations, which made it possible to determine the volume fraction of oriented nanocrystals. The orientational effect is presumably caused by both the macroscopic fields of elastic stresses in the film and the local fields of elastic stresses around the nanocrystals.

Polarization effects in gases are investigated by two methods of coherent spectroscopy - stimulated photon echo in molecular gas and laser-induced fluorescence in atomic vapour. A well developed photon echo experimental technique permitted us not only to measure relaxation rates of population, orientation and alignment on degenerated resonant levels in molecular gas but also to study their dependence on particles' longitudinal velocity. The degree of polarization of laser-induced fluorescence in Yb vapour in a mixture with Xe proves a large contribution of depolarizing collisions. The complicated non-exponential fluorescence decay at higher Yb pressures is explained by the radiation trapping.

Thylakoids of pea chloroplasts isolated from plants grown during various time intervals from June to August were subjected to fragmentation. Using a modified procedure, a fraction of larger particles was separated from those previously considered as fragments of intergranal thylakoids. The particles of the fraction isolated were identified as fragments of marginal regions of granal thylakoids (margins). The relative yield of these fragments depended on the time interval of plant growth. Two types of low-temperature fluorescence spectra corresponding to a high and low yield of the fraction were detected. The characteristics of the first one were a high fluorescence intensity in the short-wave region and the presence of bands with maxima at 687 and 696 nm emitted by photosystem II (PSII). The ratio of PSII to PSI complexes (PSII/PSI) in the fractions characterized by a low and high yield varied from 1 to 5. The analysis of excitation spectra of long-wave fluorescence of PSI showed that PSI complexes in the margin fragments obtained at a low fraction yield were depleted in chlorophyll forms with a 682-nm absorption maximum and enriched in those with a 668-nm maximum. Since an increase in the yield of the margin-fragment fraction is due to an increased unstacking of granal thylakoids, the differences in the characteristics of fragments obtained with a low and a high yield reflect the changes in the composition of granal thylakoids in the direction from the margin to the centrum, that is, a decrease in the relative content of PSI complexes and alterations in the composition and size of its light-harvesting antenna. The consistency between the data obtained and the present view concerning the different functions of PSI located in different thylakoid regions is discussed.

A photon echo induced exclusively by collisions of ytterbium atoms with buffer gas atoms has been observed at a 0 ⟷ 1-type1S0(6s2)-3P1(6s6p) 174Yb transition. The polarization properties of a collision echo and the buffer gas density dependence of its intensity agree with theoretical predictions of a model of depolarizing collisions that takes into account the dependence of a relaxation matrix on the velocity of active particles. Thus, direct experimental evidence of the relaxation anisotropy due to depolarizing collisions has been obtained.

Anisotropy of Raman scattering is observed in the system of silicon nanocrystals inside amorphous films. The observed anisotropy is established to be the result of planar correlated orientation of nanocrystals which have (1 1 0) orientation in the normal direction. Preferred orientation is proposed to be due to the deformation contribution in the process of nanocrystals formation under nanosecond laser impact.

Furnace annealing, cw- and pulse laser treatments were app lied for crystallization of amorphous Si nano-layers and Si nanoclusters in SiN x -Si 3 N 4 and Si-SiO 2 multilayer nanostructures. The as-deposite d and annealed structures were studied using optical methods and electron micros copy techniques. The influence of hydr ogen on crystallization and formation of Si nanoclusters was studied. Regimes for pulse laser crystallization of amorphous Si nanoclusters and nanolayers were found. This approach is applicable for the creation of dielectric films with semiconductor nanoclusters and silicon nanostructured films on non-refr actory substrates for all-silicon tandem solar cells. Keywords: Si based nanostructures, pulse laser crystallizatio n, Raman scattering, all-silicon tandem solar cells 1. INTRODUCTION Interest to dielectric films containing many periodical layers of Si nanoclusters or Si quantum wells is growing due to their perspectives of practical application [1]. For example, growing interest to crystallization of amorphous silicon films and silicon based heterostructures on non-refractory not expensive substrates is stimulated by demands of giant microelectronics. The enlargement of sizes of flat panel displays with active thin film transistor matrix can be described as “reverse Moor’s low” [2]. Dielectric films with amorphou s or crystalline Si clusters show promise as a material for optoelectronic and flash-memory applications. The most important application areas are silicon-based optoelectronic devices, non-volatile memory, and tandem solar cells based on lateral Si/SiO

A new idea based on the collision-induced stimulated photon echo in the presence of weak longitudinal magnetic field is applied to the depolarizing collisions research in a gaseous mixture of ytterbium vapour with xenon. Comparison of experimental data with theoretical prediction for the collision-induced stimulated photon echo in the weak magnetic field shows that the alignment decay rate of state 3P1 in 174Yb is higher than the orientation decay rate.

Polycrystalline silicon films on polyimide substrates were obtained by a method based on the crystallization of amorphous films under the impact of nanosecond pulses of excimer laser radiation. Characteristics of the film structure were studied by methods of Raman scattering and high-resolution electron microscopy. For the laser crystallization regimes employed, nanocrystalline silicon films with an average grain size of 5 nm were obtained. The results are of interest for the development of large-scale microelectronic devices (active thin-film transistor matrices) on cheap flexible substrates.

A collision-induced photon echo arising at the transition $0\ensuremath{\leftrightarrow}1$ of ytterbium in the presence of heavy atomic buffer is investigated. Collision-induced echo signal appears in the case of mutually orthogonal linear polarizations of exciting pulses and it is absent without buffer. Collision-induced echo power grows with buffer pressure up to the maximum value and decays exponentially at further buffer pressure growth. Collision-induced echo power is essentially less than that of the ordinary echo generated by pulses with parallel polarizations in the same mixture, and its polarization is linear with the polarization vector directed along that of the first exciting pulse. All the properties of collision-induced photon echo are explained on the basis of collision relaxation dependence on the direction of active atom velocity.

Characterisation of three-layer dielectric embedded into MDS-structure (Metal-Dielectric-Silicon) was provided in the dark and under light illumination. In the dark, increasing of differential capacitance, simultaneously, with variation of differential conductivity of MDS-structures was detected. In the light strong changing of capacitance part of impedance was firstly observed, demonstrating decreasing almost to zero values and restoring up to maxim al values in narrow bands of voltage applied. Variation of capacitance exceeds significantly so called dielectric layer capacitance, what interpreted as carriers exchanging between substrate and electronic states in SiN x probably due to three-layered kind of its nature. Keywords: silicon nanocrystals, non-volatile memory, Raman scattering, photoluminescence 1. INTRODUCTION Attraction of silicon nanocrystals connected with their possible application in non-volatile memory. Earlier, laser treatment was shown to be a useful tool for modification of Si clusters in silicon nitride films, been deposited by pyrolytic decomposition method [1]. In this work we investigated silicon-nitride films with silicon clusters produced by plasma-chemical vapor deposition technique. This deposition technique provides essentially lower deposition temperatures, what could be important for some applications, in particular, for flat display technologies. Equipping flat display with memory elements made within on-chip low temperature technology looks very promising for further development in this area. Moreover, varying band gap of SiN