Search

The aim of this work was the formation of multilayer structures of macroporous silicon and the study of their structural, morphological, and optical properties in comparison with the properties of multilayer structures of mesoporous silicon. The paper presents the results of the development of techniques for the formation of multilayer structures of porous silicon por-Si by stepwise change in the current with two-stage modes of electrochemical etching.The data on the morphology, composition, and porosity of macroporous and mesoporous silicon samples were obtained using scanning electron microscopy, IR spectroscopy, and X-ray reflectivity. It was shown that with the two-stage growth of porous silicon layers, the depth of the boundary between the layers of the structure was determined by the primary mode of electrochemical etching, while the total layer thickness increased with an increase in the current density of electrochemical etching.A comparative analysis of the relative intensity and fine structure of vibrational modes of IR spectra indicated a significantly more developed specific pore surface and greater sorption capacity of mesoporous silicon as compared to macroporous silicon. REFERENCES 1. Pacholski C. Photonic crystal sensors based on porous silicon. Sensors. 2013;13(4): 4694–4713. https://doi.org/10.3390/s130404694 2. Harraz F. A. Porous silicon chemical sensors and biosensors: A review. Sensors and Actuators B: Chemical. 2014;202: 897–912. https://doi.org/10.1016/j.snb.2014.06.0483. Qian M., Bao X. Q., Wang L. W., Lu X., Shao J., Chen X. S. Structural tailoring of multilayer porous silicon for photonic crystal application. Journal of Crystal Growth. 2006;292(2): 347–350. https://doi.org/10.1016/j.jcrysgro.2006.04.0334. Len’shin A. S., Kashkarov V. M., Turishchev S. Yu., Smirnov M. S., Domashevskaya E. P. Effect of natural aging on photoluminescence of porous silicon. Technical Physics Letters. 2011;37(9): 789–792. https://doi.org/10.1134/S10637850110901245. Kheifets L. I., Neimark A. B. Multiphase processes in porous media. Moscow: Khimiya Publ.; 1982. 320 p. (In Russ.)6. Canham L. Handbook of porous silicon. Switzerland: Springer International Publishing; 2014. 733 p.7. Zimin S. P. Porous silicon – material with new properties. Soros Educational Journal. 2004;8(1): 101–107. Available at: http://window.edu.ru/resource/217/21217/files/0401_101.pdf (In Russ., abstract in Eng.) 8. Seredin P. V., Lenshin A. S., Goloshchapov D. L., Lukin A. N., Arsentyev I. N., Bondarev A. D., Tarasov I. S. Investigations of nanodimensional Al2O3films deposited by ion-plasma sputtering onto porous silicon. Semiconductors. 2015;49(7): 915–920. https://doi.org/10.1134/S10637826150702109. Seredin P. V., Lenshin A. S., Mizerov A. M., Leiste H., Rinke M. Structural, optical and morphological properties of hybrid heterostructures on the basis of GaN grown on compliant substrate por-Si(111). Applied Surface Science. 2019;476: 1049–1060. https://doi.org/10.1016/j.apsusc.2019.01.23910. Seredin P. V., Leiste H., Lenshin A. S., Mizerov A. M. Effect of the transition porous silicon layer on the properties of hybrid GaN/SiC/por-Si/Si(111) heterostructures. Applied Surface Science. 2020;508(145267): 1–14. https://doi.org/10.1016/j.apsusc.2020.14526711. Lenshin A. S., Barkov K. A., Skopintseva N. G., Agapov B. L., Domashevskaya E. P. Influence of electrochemical etching modes under one stage and two Stage formation of porous silicon on the degree of oxidation of its surface layer under natural conditions. Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases. 2019;21(4): 534–543. https://doi.org/10.17308/kcmf.2019.21/2364 (In Russ., abstract in Eng.) 12. Buttard D., Dolino G., Bellet D., Baumbach T., Rieutord F. X-ray reflectivity investigation of thin p-type porous silicon layers. Solid State Communications. 1998;109(1): 1–5. https://doi.org/10.1016/S0038-1098(98)00531-613. Lenshin A. S., Seredin P. V., Agapov B. L., Minakov D. A., Kashkarov V. M. Preparation and degradation of the optical properties of nano-, meso‑,and macroporous silicon. Materials Science in Semiconductor Processing. 2015;30: 25–30. https://doi.org/10.1016/j.mssp.2014.09.04014. Ksenofontova O. I., Vasin A. V., Egorov V. V., Bobyl’ A. V., Soldatenkov F. Yu., Terukov E. I., Ulin V. P., Ulin N. V., Kiselev O. I. Porous silicon and its applications in biology and medicine. Technical Physics. 2014;59(1): 66–77. https://doi.org/10.1134/S1063784214010083

Nanocrystalline PdO films have been characterized by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The results demonstrate that thermal oxidation in an O2 atmosphere causes ~35-nm-thick nanocrystalline Pd films on SiO2/Si(100) substrates to undergo a sequence of phase transformations resulting in PdO formation, followed by PdO decomposition into metallic Pd at T > 1120 K. In the range 670–970 K, the a and c tetragonal cell parameters of the nanocrystalline PdO films increase monotonically with increasing temperature. The present and previously reported data have been used to construct a model for the unit cell in the crystal structure of palladium(II) oxide. Based on the quasi-chemical approach, we propose a model that accounts for the observed increase in the tetragonal cell parameters and the p-type conductivity of the nanocrystalline PdO films in terms of the formation of excess interstitial oxygen atoms.

В работе методами растровой электронной микроскопии и ультрамягкойрентгеновской эмиссионной спектроскопии были проведены исследования особенностейформирования многослойных структур пористого кремния и установлено влияние изменения плотности тока при электрохимическом травлении монокристаллических пластин кремния на фазовый состав поверхностных слоев сформированной пористой структуры. ЛИТЕРАТУРА1. Moshnikov V., Gracheva I., Lenshin A., Spivak Yu. Porous silicon with embedded metal oxides for gassensing applications // Journal of Non-Crystalline Solids, 2012 v. 358(3), pp. 590–595. DOI: https://doi.org/10.1016/j.jnoncrysol.2011.10.0172. Pacholski C. Photonic crystal sensors based on porous silicon // Sensors, 2013, v. 13(4), pp. 4694–4713.DOI: https://doi.org/10.3390/s1304046943. Harraz F. Porous silicon chemical sensors and biosensors: A review // Sensors and Actuators B, 2014,v. 202, pp. 897–912. DOI: https://doi.org/10.1016/j.snb.2014.06.0484. Jane A., Dronov R., Hodges A., Voelcker N. Porous silicon biosensors on the Advance // Trends in Biotechnology, 2009, v. 27(4), pp. 230–239. DOI: https://doi.org/10.1016/j.tibtech.2008.12.0045. RoyChaudhuri C. A review on porous silicon based electrochemical biosensors: beyond surface areaenhancement factor // Sensors and Actuators B: Chemical, 2015, v. 10, pp. 310–323. DOI: http://dx.doi.org/10.1016/j.snb.2014.12.0896. Canham L. Properties of porous silicon. Ed. by Canham L., Malvern: DERA, 1997, 400 p.7. Lenshin A., Kashkarov V., Spivak Yu., Moshnikov V. Investigations of nanoreactors on the basisof p-type porous silicon: Electron structure and phase composition // Materials Chemistry and Physics, 2012,v. 135(2–3), pp. 293–297. DOI: https://doi.org/10.1016/j.matchemphys.2012.03.0958. Lenshin A., Kashkarov V., Turishchev S., Smirnov M., Domashevskaya E. Effect of natural aging onphotoluminescence of porous silicon // Technical Physics Letters, 2011, v. 37(9), pp. 789-792. DOI: https://doi.org/10.1134/s10637850110901249. Seredin P., Lenshin A., Goloshchapov D., Lukin A., Arsentyev I., Bondarev A., Tarasov I. Investigationsof nanodimensional Al2O3 fi lms deposited by ion-plasma sputtering onto porous silicon // Semiconductors,2015, v. 49(7), pp. 915–920. DOI: https://doi.org/10.1134/s106378261507021010. Qian M., Bao X.Q., Wang L.W., Lu X., Shao J., Chen X.S. Structural tailoring of multilayer poroussilicon for photonic crystal application. // Journal of Crystal Growth, 2006, v. 292(9), pp. 347–350. DOI:https://doi.org/10.1016/j.jcrysgro.2006.04.03311. Verma D., Khan F., Singh S. Correlation between refl ectivity and photoluminescent properties ofporous silicon fi lms // Solar Energy Materials & Solar Cells, 2011, v. 95(1), pp. 30–33. DOI: https://doi.org/10.1016/j.solmat.2010.05.03012. Theiß W. The dielectric function of porous silicon – how to obtain it and how to use it // ThinSolid fi lms, 1996, v. 276 (1–2), pp. 7–12. DOI: https://doi.org/10.1016/0040-6090(95)08036-813. Caballero-Hernandez J., Godinho V., Lacroix B., Haro M., Jamon D., Fernandez A. Fabrication of opticalmultilayer devices from porous silicon coatings with closed porosity by magnetron sputtering // ACS Appl.Mater. Interfaces, 2015, v. 7(25), pp. 13889–13897. DOI: https://doi.org/10.1021/acsami.5b0235614. Terekhov V, Kashkarov V, Manukovskii E., Schukarev A., Domashevskaya E. Determination of thephase composition of surface layers of porous silicon by ultrasoft X-ray spectroscopy and X-ray photoelectronspectroscopy techniques // J. Electron. Spectrosc., 2001, v. 114–116, pp. 895–900. DOI: https://doi.org/10.1016/s0368-2048(00)00393-515. Shulakov A. X-ray emission depth-resolved spectroscopy for investigation of nanolayers. // Journalof Structural Chemistry, Supplement, 2011, v. 52(S1), pp. 1–12. DOI: https://doi.org/10.1134/s002247661107001816. Mashin A., Khokhlov A., Mashin N., Domashevskaya E., Terekhov V. X-ray spectroscopic studyof electronic structure of amorphous silicon and silicyne // Semiconductors, 2001, v. 35(8), pp. 956–961.DOI: https://doi.org/10.1134/1.139303517. Domashevskaya E., Kashkarov V., Manukovskii E., Shchukarev A., Terekhov V. XPS, USXS and PLSinvestigations of porous silicon // J. Electron. Spectrosc., 1998, v. 88–91, pp. 969–972. DOI: https://doi.org/10.1016/s0368-2048(97)00274-018. Lenshin A., Kashkarov V., Domashevskaya E., Bel’tyukov A., Gil’mutdinov F. Investigations of thecomposition of macro-, micro- and nanoporous silicon surface by ultrasoft X-ray spectroscopy and X-rayphotoelectron spectroscopy // Applied Surface Science, 2015, 359, pp. 550–559. DOI: https://doi.org/10.1016/j.apsusc.2015.10.14019. Suriani Yaakob, Mohamad Abu Bakar, Jamil Ismail, Noor Hana Hanif Abu Bakar, KamarulaziziIbrahim. The formation and morphology of highly doped N-type porous silicon: effect of short etchingtime at high current density and evidence of simultaneous chemical and electrochemical dissolutions //Journal of Physical Science, 2012, v. 23(2), pp. 17–31. Available at: http://jps.usm.my/wp-content/uploads/2014/10/23.2.2.pdf (accessed 11.11.2019)

We develop a technique for the sorption of inulinase from Kluyveromyces marxianus on the KU-2 matrix cation-exchanger. The most appropriate conditions for immobilization are: 25 °C, pH 4.5, incubation time 1.5 h, protein content during immobilization 10 mg/g of carrier. At higher (20–100 mg/g) concentrations, inulinase forms local high-concentration domains on the ion-exchanger surface, the enzyme is adsorbed on the protein, not on the carrier. 62% of the initial catalytic activity of inulinase is immobilized on KU-2 by the adsorption method. Upon the enzyme immobilization on KU-2, the number of unordered structures in the protein is reduced by ~10%, that points to the compaction of the molecule. Hydrogen bonds are formed only between the sulfo groups of carrier and the protein molecule, without affecting other structures of the cation exchanger. The highest activity of the inulinase immobilized on KU-2 was observed at 70 °C (cf. 50 °C for the native enzyme). Heating of the solution for 60 min in the temperature range of 50–80 °C failed to inactivate completely the immobilized enzyme; the complete loss of its ability to hydrolyze inulin was achieved only after more than 1 h incubation at 90 °C.

Objective – risk-oriented assessment of the current epidemiological situation on West Nile fever in the Astrakhan Region.Materials and methods. Utilized were the data collected by the Astrakhan Plague Control Station, Rospotrebnadzor Administration in the Astrakhan Region, and A.M. Nichoga Regional Infectious Clinical Hospital. The key method of study was epidemiological analysis of West Nile fever incidence among the population of the Region during the period of 2000–2016. 145 case records were investigated.Results and discussion. Retrospective analysis provided for identification and featuring of the main categories of epidemiological risk of infection with West Nile fever in the Astrakhan Region in 2000–2016. It was established that men of 19 to 70 age range ( 82.1 %) are infected more often (95 out of 145 – 65 %). WNF infections in women occur among the same age group (75.8 %), and also among children aged below 6 years old (9.0 %). Analysis of the risk territories showed that the level of risk is high in one district, medium – in one district, low – in four districts, and very low – in six. When investigating the conditions of infection (risk factors) with WNF, it was determined that in the majority of cases (107 – 73.8 %) the risk factors were not specified. Out of those that were identified, one should pinpoint the bite of mosquito inside the households, basements, while fishing (16.3 %), as well as the bite, removal or squashing of a tick with unprotected hands (6.9 %). The period of the highest risk is from May to October with the maximum values of incidence in August (55.1 %).

Lead telluride films have been grown on Si (100) and BaF2 (100) substrates by a modified hot-wall method using a graphite reaction chamber. According to X-ray diffraction, X-ray microanalysis, and scanning electron microscopy characterization results, the average growth rate of PbTe films having compositions within the homogeneity range of lead telluride increases with increasing lead vapor partial pressure and decreases with increasing tellurium vapor partial pressure, independent of the nature of the substrate. The rate of PbTe film growth has been shown to be maximal in the initial stage of the process and decrease monotonically over time, independent of the nature of the substrate. Independent of the growth time, the average growth rate of the PbTe films on the Si (100) substrates is considerably higher than that on the BaF2 (100) substrates. Reflection high-energy electron diffraction data indicate that the texture of the PbTe films on Si (100) corresponds to the substrate orientation and that the misorientation angle of the mosaic blocks does not exceed 20°. On the BaF2 (100) substrates, we observe epitaxial PbTe film growth with the orientation relationship (100), [011] PbTe ║ (100), [011] BaF2.

Методами растровой электронной микроскопии, локального рентгеноспектрального анализа, рентгенофазового анализа и атомно-силовой микроскопии изучен количественный элементный состав, фазовая природа, а также морфология поверхности гомогенных пленок теллурида свинца, синтезированных модифицированным методом «горячей стенки» на подложках Si (100). При повышении температуры Si (100) подложки до Т = 593 - 608 К синтезированы мозаичные монокристаллические пленки PdTe с текстурой (100). Установлено, что повышение температуры Si подложки при остальных постоянных режимах синтеза способствует увеличению средних латеральных размеров кристаллитов пленок. Показано, что средняя величина латеральных размеров кристаллитов пленок PbTe на подложках Si (100) увеличивается с ростом толщины и продолжительности синтеза. Установлено, что средние значения шероховатости пленок PbTe/Si (100) увеличиваются с ростом средней толщины пленок PbTe. При этом поликристаллические пленки PbTe/Si (100) при одинаковых значениях средней толщины характеризуются более высокими значениями шероховатости по сравнению с мозаичными монокристаллическими образцами PdTe (100). Экспериментальные исследования были проведены с помощью научно-технической базы ЦКПНО ВГУ.

Using scanning electron microscopy and infrared spectroscopy, some peculiarities in the formation of multilayer porous silicon were investigated. The effect of the changes in the current density during electrochemical etching of silicon on the composition of chemical bonds for the obtained porous structure was found.

Nanofilms have been grown on InP in the presence of V2O5 introduced into the system by different procedures and methods (within one procedure) and their thickness has been determined by spectral ellipsometry. The phase composition of the films has been determined by X-ray diffraction, and their surface morphology and structure have been analyzed by atomic force microscopy and transmission electron microscopy. The characteristics of the films have been shown to depend on the procedure (through the gas phase in the course of oxidation or by deposition on the surface before oxidation) and method (magnetron sputtering or deposition from gel) used to introduce the chemical stimulator into the system.

In the work some peculiarities in formation of the porous silicon, its morphology and composition were investigated, as well as some optical properties of this material. Porous silicon was obtained on the substrates of single-crystalline Si as well as on the silicon structures with p–n junctions. In order to obtain nano-, meso- and macroporous silicon as well as multi-layered porous structures several technological parameters (were controlled) varied—orientation of the substrates, conductivity type and composition of the etchant. Correlation between photoluminescence intensity of the obtained samples and intensity of the absorption band in their IR spectra (the band at 616 cm −1 ) that is due to the presence of Si–Si bonds in porous layer was observed. The influence of the porous silicon storage in the air on the degradation of its photoluminescence parameters was also estimated.

Porous silicon (por-Si) has a unique combination of physicochemical parameters: well-developed surface and hence high sorption. Depending on technology it is possible to form nanometer size pores and clusters in porous silicon which makes this material promising for developments in the field of optoelectronics and sensors. However the high surface activity makes por-Si unstable when exposed to atmosphere. In this work we have studied the effect of por-Si surface treatment in a polyacrylic acid water solution on the composition and photoluminescence (PL) of the material. Por-Si was produced from two fluoric acid solutions. One was a standard solution of fluoric acid, isopropyl alcohol and hydrogen peroxide, and the other was a mixture of fluoric acid and dimethylformamide. We have shown that depending on por-Si technology, its treatment in polyacrylic acid solution allows increasing and stabilizing por-Si PL or changing PL band position and significantly increasing its integral intensity.

The composition and optical properties of composite materials based on porous silicon with iron, cobalt, and nickel deposited by the sol-gel technique are studied. It is shown that the deposition of metal-oxide films onto the surface of porous silicon enables stabilization of the photoluminescence and an increase in its intensity, as well as the storage of hydrogen in the porous layer.

Morphology, composition, and optical properties of porous silicon on single-crystal-silicon substrates and p-n junctions are studied. Substrate orientation, type of conduction, and composition of etching agent are varied to obtain nano-, meso-, and microporous silicon and multilayer porous structures. A correlation of the photoluminescence intensity and intensity of the IR absorption band peaking at 616 cm−1 is related to the presence of Si-Si bonds.

The morphology of the surface of MK-40 and MA-40 ion-exchange membranes in the swollen state after chemical and thermal treatment is studied using scanning electron microscopy. The distribution of portions of the ion exchanger on the surface of heterogeneous membranes is found to be of a complex stochastic nature; their sizes for the MK-40 and MA-40 membranes are 5–30 and 8–40 μm, respectively, while the sizes typical for the secondary porous structure are 2–8 μm. An increase in the share of the ion-exchange component of the surface (by 20–40%), the sizes of the ion-exchange portions (by 20%), and the surface porosity (by two-three times) in the samples subjected to thermal treatment is revealed.

Evolution of morphology of surface and the composition of layer near the surface in the process of thermooxidation of V x O y /InP formed by soft and hard methods is shown. Dependence of morphology of film surface on the way of application of chemostimulator and the regime of thermooxidation is established. Both methods permit to obtain layers with the sufficiently smooth surface, but while using the hard method nanostuctured films are finally formed.

Hydroxyapatite (HAP) is a substance that is most actively used in orthopedia and dentistry as a biocoating of implants in order to improve its osteointegration with bone tissue. HAP was synthesized by precipitation technique with the use of the biological source — hen's eggshell. X-ray diffraction (XRD) investigations, IR-spectroscopy, scanning electron microscopy (SEM) demonstrate that the obtained powder-like material in the form of globules from 4 to 5 μm in size is single-phase, thermally stable up to 900 °C and morphologically uniform. The globules consist of nanocrystals with the average size of about 30 nm.

The structural and optical properties of porous silicon prepared by anodic etching of an n-Si(111) wafer with a p +-homoepitaxial layer on one side are studied by scanning electron microscopy and multiple-crystal X-ray diffraction. A considerable difference between the microstructures on the sides of the wafer is found. Upon aging for 4.5 months, diffraction peaks of the por-Si structures shift from that of the substrate by δθ = −42″ for the n-Si porous layer and −450″ for the p +-Si porous layer. The photoluminescence band associated with the p +-layer is twice as narrow as the band associated with the n-layer and is shifted toward shorter wavelengths (higher energies) by 0.4 eV, with the intensities of the bands being the same.

We investigate the change in the composition and optical properties of porous silicon (por-Si) obtained by electrochemical etching of a palate made of n-type (111) silicon single crystal under high-temperature annealing and processing in tetraethyl orthosilicate (TEOS). It is shown that TEOS processing and annealing prevent contamination of a sample stored for a long time in atmosphere. The processing of por-Si in TEOS does not change the position of the photoluminescence (PL) peak and suppresses PL to a smaller extent as compared to annealing of por-Si. This increases the reliability of optoelectronic devices based on por-Si.

The chemical modification of porous silicon (PS) surfaces makes it possible to eliminate weak silicon-hydrogen bonds and prevent the formation of Si-O and Si-OH groups deep in pores and on a corrugated silicon surface. Hence, the effect of PS aging is not observed during its storage in air, and the porous layer’s composition is stable. Surfaces have been modified in polyacrylic acid solutions. The surface composition is analyzed on the basis of X-ray absorption spectra, and the morphology is investigated via scanning electron microscopy. It has been ascertained that the composition and morphology of a surface treated in polyacrylic acid solutions depend on the PS preparation method.

X-ray electron probe microanalysis (EPMA) was used to study the concentration profiles of the main reaction components in the Ga2Se3-GaAs heterojunction obtained as a result of thermally stimulated heterovalent anion substitution. It has been found that the quasi-equilibrium and quasi-steady diffusion modes for delivery of chalcogen to the reaction zone are different with respect to the kinetics of the A2IIIC3VI layer growth. Independent of this, the concentration profiles of the reaction elements are self-organized with time, which allows heterostuctures with a sharp interphase boundary to be reproduced.

The surface of GaAs(100) and InAs(100) substrates thermally treated in selenium vapor has been investigated by transmission electron microscopy (TEM) and reflection high-energy electron diffraction. Transmission electron microscopy and high-energy electron diffraction data on these heterostructures confirms the epitaxial pseudomorphic growth of the gallium selenide Ga2Se3(100) and indium selenide In2Se3(100) phases with ordered stoichiometric cation vacancies. A model of the atomic structure of the Ga2Se3(100) and In2Se3(100) surfaces is proposed, and the 2 × 2 reconstruction of the GaAs(100) and InAs(100) surfaces after treatment in selenium vapor is discussed within this model.

The surface of GaAs(111) and InAs(111) substrates has been investigated by transmission and scanning electron microscopy after thermal treatment in selenium vapor. A pseudomorphic growth of single-crystal phases of indium selenide In2Se3(111) and gallium selenide Ga2Se3(111) is found; these compounds are crystallized into a sphalerite lattice with ordered stoichiometric cation vacancies. A model of an atomic surface is proposed for the In2Se3(111) and Ga2Se3(111) structures. The reconstruction of the (√3 × √3)-R30° surface of GaAs(111) and InAs(111) after treatment in Se vapor is considered within this model.

Hydroxyapatite nanoparticles were obtained in the course of reaction in microemulsion system stabilized by surfactant (sodium bis-2-ethylhexylsulfosuccinate). By the methods of X-ray phase analysis, IR spectroscopy, elemental analysis, and electron microscopy the presence of crystals in the samples of hydroxyapatite as the main phase, and detected the formation of additional calcium phosphate compounds was demonstrated.

The effect of the nature of bath anions (Cl−, SO 4 2− and CH3COO−) on the characteristics of the electrochemical plating of nickel coatings, namely, parameters of the cathodic polarization curves, bath stability, and current efficiency, as well as the composition and morphology of deposits and their catalytic activity in the anodic oxidation of hypophosphite ions and cathodic evolution of hydrogen, is studied. The anionic composition of the baths is found to substantially affect not only the kinetics of the deposit growth, but also the properties of the deposit. The differences observed are determined by the complex-forming and buffering properties of the anions.

A method for the galvanic deposition of iron-group metals onto porous silicon (por-Si) substrates has been developed. The morphology and phase composition of por-Si nanocomposites containing galvanically deposited particles of Fe, Co, and their mixtures have been studied by scanning electron microscopy (SEM), ultrasoft X-ray emission spectroscopy (USXES), and X-ray absorption near-edge structure spectroscopy (XANES) techniques. It is established that iron uniformly covers the surface of porous silicon, whereas cobalt penetrates deep into pores in the form of nanoparticles. During the galvanic codeposition of both metals from a mixed solution of their salts, cobalt favors the penetration of iron in depth of the pores.

Porous silicon is an utterly unique material. Since 1990 when Canhem revealed visible photo-luminescence in por-Si [1], the number of publications concerned with technology of its producing, the study of its properties as well as its real and possible applications in various fields of science and industry continuously grows. Fabrication of porous silicon is based on the etching (chemical or electrochemical) of the wafers of single- or poly-crystalline Si. Fluoric acid (HF) is applied as one of the main components in solutions for etching. However, this acid is a potent substance and is really dangerous for the human health and can be hazardous for the environ-ment. Therefore, we have tested and improved an alternative technique for electrochemical etching of silicon [2, 3], where the concentrated aqueous solution of ammonium fluoride NH4F is used instead of HF. Since mobility of NH ions in aqueous solution is much less than that one for hy-drogen ions if HF solution is used as an etchant then sili-con is etched at a less rate. Therefore, a strong oxidant must be added to the solution, in our case it was nitric acid. The aim of this work was the study of the properties of por-Si obtained with the use of this new improved tech-nique of etching. For the analysis we applied the following experimental techniques: scanning electron microscopy (SEM), ultrasoft X-ray emission spectroscopy (USXES), X-ray absorption spectroscopy near absorption edge (XANES) and X-ray photoelectron spectroscopy of the core levels. Moreover, basing on the elaborated computer program [4] an estimation of the phase composition for the near-surface layers of obtained por-Si was performed.

Morphology and phase composition of porous silicon with electrochemically deposited Fe and Co particles as well as the particles of their mixtures were investigated by scanning electron microscopy (SEM) and X-ray emission and absorption spectroscopy. Iron was shown to cover the surface of porous silicon while cobalt penetrates inside the pores in the form of nanoparticles. Iron Iron is present in the form of the phase of Fe2O3 with an admixture of FeO and Fe3O4. Cobalt forming nanoparticles is involved as metallic Co and Co2O3. Under co-deposition of these metals from solution of their salts mixture cobalt favored penetration of iron inside the pores. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of composites by calcium phosphates with chondroitin sulfate and gelatin obtained at excess content of calcium ion in solution is studied by the methods of X-ray phase analysis, IR spectroscopy and electron microscopy. Inclusion to the crystals of hydroxyapatite as the main phase and the absence of chemical interaction of biopolymers with calcium phosphate is proved and some features of the effect of reagents addition order to the studied system calcium-ammonium hydrogen phosphate-organic component are elucidated.

Structural and optical properties of two- and three-layer epitaxial heterostructures containing GaInP/Ga x In1 − x As y P1 − y quaternary alloy layers were studied. Domain formation due to spinodal decomposition of the quaternary alloy was detected in three-layer heterostructures. As a result, an additional long-wavelength band appears in the photoluminescence spectra, and an additional doublet of the % MathType!MTEF!2!1!+- % feaagaart1ev2aaatCvAUfKttLearuqr1ngBPrgarmWu51MyVXgatC % vAUfeBSjuyZL2yd9gzLbvyNv2CaeHbd9wDYLwzYbItLDharyavP1wz % ZbItLDhis9wBH5garqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbb % L8F4rqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaqpe % pae9pg0FirpepeKkFr0xfr-xfr-xb9adbaqaaeGaciGaaiaabeqaam % aaeaqbaaGcbaaceaGaa83qaiaa-vhacqWGlbWsdaWgaaWcbaaccaGa % mair+f7aHnacas0gaaadbGaGejadaseIXaqmcWaGejilaWIamairik % daYaqajairaaWcbeaaaaa!480D! $$ CuK_{\alpha _{1,2} } $$ line appears in X-ray diffraction patterns of the (006) line. The domain composition was determined on the basis of Vegard’s law and the Kouphal equation.

Spatial separation of activator oxides in MnO2 + PbO and MnO2 + V2O5 binary compositions helps to locate the interactions between the oxides that lead to nonlinear joint effects of the compositions on GaAs thermal oxidation. The mutual enhancement of the chemostimulating activity (a positive nonlinear effect) was discovered in the solid phase, whereas vapor-phase processes led to a considerable negative nonadditivity of the joint chemostimulating effect.

The contribution from the solid-phase interactions in the PbO + Sb2O3 and PbO + Bi2O3 activating compositions to the multichannel process of GaAs thermal oxidation has been determined by spatial separation of the oxides. The solid-phase interactions make a positive contribution to the overall negative nonlinear effect in the dependence of the oxide film thickness on the GaAs surface on the activator batch composition. The contributions from the oxide interactions on the semiconductor surface and in the gas phase have been evaluated for the PbO + Sb2O3 composition.

The effect of preliminary doping of sulfo cation-exchange material KU-23 15/100S with a chemically deposited metal (Ag, Cu) on the rate of copper ion electroreduction is investigated. It is shown that the threshold dependence of the reaction current of copper electroreduction on the amount of doped metal is due to the formation of a single percolation cluster in an ion-exchange grain and, as a result, to the appearance of electron conductivity. It is established that preliminary doping changes the nucleation mechanism from a gradual to an instantaneous one. Results from a local X-ray spectral microanalysis provide the basis for concluding that copper electrodeposition is uniform throughout the volume of an ion-exchange grain. The average size of the copper particles formed is 100 nm.

The morphology and phase composition of porous silicon with galvanically deposited Fe and Co particles were investigated by ultrasoft X-ray emission spectroscopy, X-ray absorption near-edge structure spectroscopy, and scanning electron microscopy. It is shown that iron uniformly covers the surface of porous silicon, whereas cobalt penetrates into pores in the form of nanoparticles. It is established that iron is present mainly in the Fe2O3 phase with an admixture of FeO and Fe3O4. Cobalt forms a mixture of phases of metallic Co and Co2O3.

The GaAs(100)-Ga2Se3 heterostructures have been investigated by transmission and scanning electron microscopy. The sequence of structural transformations at the GaAs(100) surface during treatment in selenium vapor has been determined. It has been found that the preliminary treatment of the GaAs(100) surface in selenium vapor increases the orienting effect of the GaAs(100) substrate on the GaAs film growth.

Spatial separation of the oxides in MnO2 + PbO and MnO2 + V2O5 binary compositions activating the thermal oxidation of GaAs has made it possible to locate the interactions between these oxides that are responsible for the nonlinear effects observed in their coaction. The solid-phase interactions enhance the chemostimulating activities of both oxides (a positive nonlinear effect takes place). The gas-phase interactions cause a marked negative deviation from the additive chemical stimulation effect.

A first study of the effect of weak pulsed magnetic fields (PMFs) on Sb1−x Asx solid solution crystals is reported. An effect of long-time (months) redistribution of the solid solution components at room temperature after a short (seconds) exposure to a PMF was revealed. The effect includes stages of enrichment of the crystal surface in antimony with the formation of clusters, antimony cluster breakup, and a decrease in surface antimony content, which is accompanied by a substantial improvement in solid-solution homogeneity. The PMF-induced component redistribution entails a decrease in the crystal melting temperature. Rupture of stressed chemical bonds in arsenic vacancy complexes, which is induced by a change in their multiplicity under PMF exposure, is considered as a possible trigger mechanism.

Data on the evaporation behavior of Pb1 – xInx (0.10 ≤ x ≤ 0.70) melts were used to devise a procedure for the growth of vapor-phase In doped PbTe thin films on Si substrates. This approach offers the possibility of growing single-phase, homogeneous Pb1 – yInyTe films of controlled composition by adjusting the composition and temperature of Pb1 – xInx (0.10 ≤ x ≤ 0.50) melts. X-ray diffraction characterization demonstrates that the films grown on Si with no oxide layer consist of slightly misoriented crystallites, with their (100) axes normal to the film surface, whereas the films grown on substrates covered with a SiO2 layer are polycrystalline, with a strong (100) texture.

In depositing thin PbTe〈Ga〉 films onto Si and SiO2 /Si substrates by the hot-wall method, Pb1 – x Ga x melts were used as Ga vapor sources in combination with separate Pb and Te vapor sources. The vaporization of Pb1 – x Ga x (0.15 ≤ x≤ 0.95) melts was studied between 1000 and 1300 K in the reaction chamber of the deposition unit. Using electron probe x-ray microanalysis, all the deposited films were shown to contain Ga. Pb1 – x Ga x melts were also used as separate Pb and Ga vapor sources.

In2Se3/InAs heterojunctions prepared by heterovalent substitution via annealing in Se vapor in a quasi-closed reactor were studied by scanning electron microscopy, electron-probe x-ray microanalysis, and electron diffraction in reflection and transmission.