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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)

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.

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.

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.

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.

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.