Photosensitive porous silicon based structures

We present results of electrical and photoelectrical measurements on two types of Al/porous silicon (PS)/monocrystalline silicon (c-Si)/Al sandwich structures with thin and thick PS layers obtained by stain etching. Current-voltage characteristics and photosensitivity spectra indicate that for structures with a thin PS layer the photosensitivity is determined by PS/c-Si heterojunctions (HJ), while for structures with a thick PS layer – by the PS layers themselves. The properties of PS/c-Si HJ were explained in the framework of a band diagram of the isotype HJ with opposite band bendings on the sides due to a high concentration of defect centers at the heterointerface. PS layers exhibit photoconduction with the photosensitivity maximum at 400–500 nm. The results are compared with those obtained for the structures based on PS layers prepared by electrochemical anodization.Представлені результати електричних та фотоелектричних вимірювань двох типів Al/пористий кремній (ПК)/монокристалічний кремній (c-Si)/Al сендвич структур с тонкими та товстими шарами ПК, що одержані хімічним забарвлюючим травленням. Вольт-амперні характеристики та спектри фотовідгуків свідчать про те, що фоточутливість структур з тонкими шарами ПК переважно визначається гетеропереходом (ГП) ПК/c-Si, а з товстими . ПК шарами. Властивості ГП з.ясовані в рамках зонної діаграми ізотипного ГП з протилежними напрямками вигину зон по обидва боки переходу завдяки високій концентрації дефектів на межі розподілу. ПК шари . фоточутливі, з максимумом чутливості біля 400,500 нм. Результати порівнюються з такими для структур на основі шарів ПК, що одержані eлектрохімічним травленням.Представлены результаты электрических и фотоэлектрических измерений двух типов Al/пористый кремний (ПК)/ монокристаллический кремний (c-Si)/Al сэндвич структур с тонкими и толстыми слоями ПК, полученными химическим окрашивающим травлением. Вольт-амперные характеристики и спектры фотооткликов свидетельствуют, что фоточувствительность структур с тонкими слоями ПК определяется гетеропереходом (ГП) ПК/c-Si, а с толстыми . ПК слоями. Свойства ГП объяснены в рамках зонной диаграммы изотипного ГП с противоположными направлениями изгибов зон по обе стороны перехода из-за высокой концентрации дефектов на гетерогранице. ПК слои . фотопроводящие с максимумом фоточувствительности при 400,500 нм. Результаты сравниваются с таковыми для структур на основе слоев ПК, полученных электрохимическим травлением

Raman and Photoluminescence Study of ZnO Films Grown by Chemical Method

In this paper phonon and emission properties of ZnO films grown by metalorganic chemical vapour deposition (MOCVD) at ambient pressure and by molecular beam epitaxy (MBE) are investigated using Raman and photoluminescence (PL) spectroscopy. It is shown that high-frequency shift of non-polar phonon modes corresponds to elastic compressive strain in the plane parallel to c-axis and is equal to 3.2×10−3 and 2.2×10−3 for ZnO film grown by MOCVD and MBE, respectively. The possibility of obtaining highquality ZnO films grown by MOCVD was demonstrated. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3501

SrTiO₃:Eu³⁺ phosphors prepared by sol-gel synthesis: Structural characterization, magnetic properties and luminescence spectroscopy study

We report the results of the comprehensive study of the structural, magnetic and optical properties of SrTiO₃ perovskite doped with Eu³⁺ ions. Polycrystalline powders were obtained by sol-gel process including high-temperature annealing at 1300 °C. The structural analysis showed that material is composed of several phases with dominant SrТiO₃ and onsiderable quantity of titanium dioxide (rutile, 10…20%). Both the amount of Eu and ratio of Eu:Sr in the final product are considerably smaller as compared to the original solutions for synthesis. The elemental analysis reveals europium only in the phase of EuSrTi₂O₇ compound for equimolar ratio of Eu and Sr during the synthesis. The EPR analysis reports deficiency of Eu²⁺ in the samples under investigations. SrTiO₃:Eu³⁺ powders demonstrate weak photoluminescence, which intensity grows up with increasing the concentration of Eu and reaches its maximum at c.a. 8 mol.% of Eu in the original solutions. Addition of Al increases the intensity of photoluminescence (c.a. 2.2 for 10 mol.%). Emission spectra are typical for Eu³⁺ occupied sites with high symmetric environment (dominant ⁵D₀→⁷F₁ transition) with relatively low distortion (both ⁵D₀→⁷F₂ and ⁵D₀→⁷F₄ as well present, but with a lower intensity) of coordination polyhedron. Low solid-solubility limit of Eu³⁺ in perovskite matrix (less than 1 mol.%), peculiarities of optical spectra, effect of Al, production/annealing temperature dependence etc. have suggested that structural effects are dominating in functional, in particular, optical properties of SrTiO₃:Eu³⁺ phosphors

Electroreflectance spectroscopy and scanning electron microscopy study of microrelief silicon wafers with various surface pretreatments

The effect of various pretreatments on the performance of microrelief (textured) Si wafers was studied by the techniques of low-field electroreflectance spectroscopy, scanning electron microscopy, and electron diffraction. Four types of preliminary treatments were employed to prepare microrelief surfaces by anisotropic chemical etching: (i) cutting, (ii) cutting and mechanical polishing with Al₂O₃, (iii) cutting and chemical polishing with HNO₃:HF, and (iv) the standard industrial technique. Using the critical point energy Eg at the central point in the Brillouin zone (GIV₂₅ – GC₁₅ transition) and the phenomenological parameter of broading G to characterize the performance of the Si surface, it was found that anisotropic chemical etching performed after cutting produced the surface performance comparable to that of industrially fabricated wafers, but at a lower cost.Методами спектроскопії низькопольового електровідбиття, растрової електронної мікроскопії та електронографії досліджено вплив попередніх обробок поверхні кремнію (різка; різка та механічна поліровка; різка та хімічна поліровка; стандартна фабрична обробка) на досконалість анізотропно травлених мікрорельєфних пластин. Як критерій досконалості аналізуються енергія критичної точки Eg в центрі зони Бріллюена (переходи GIV₂₅ – GC₁₅ ), феноменологічний параметр уширення Г, рухливість носіїв заряду, морфологічні особливості поверхні та кристалічна структура. Показана можливість використання попередньої обробки різкою для виготовлення достатньо досконалих анізотропно травлених мікрорельєфних пластин. При цьому очікується зменшення їх кошторису.Методами спекроскопии низкополевого электроотражения, растровой электронной микроскопии и электронографии исследовано влияние предварительных обработок поверхности кремния (резка; резка и механическая полировка; резка и химическая полировка; стандартная фабричная обработка) на совершенство анизотропно травленных микрорельефных пластин. В качестве критерия совершенства анализируются энергия критической точки Eg в центре зоны Бриллюэна (переходы GIV₂₅ – GC₁₅, феноменологический параметр уширения Г, подвижность носителей заряда, морфологические особенности поверхности и кристаллическая структура. Сделан вывод о возможности использования предварительной обработки резкой для получения достаточно совершенных анизотропно травленных микрорельефных кремниевых пластин. При этом ожидается снижение стоимости пластин

Investigation of growth conditions, crystal structure and surface morphology of SmS films fabricated by MOCVD technique

The polycrystalline SmS films were fabricated by MOCVD technique using a number of ditiocarbamates, synthesized by different techniques. The growth kinetics and temperature dependencies of the film growth rate are investigated, which allowed us to determine the activation energies and the reaction type. The investigations of the structure and surface morphology of films were carried out. The technological conditions are determined providing the fabrication of single-phase SmS films of cubic modification with the most ordered crystal structure

Photoluminescent films of nanocrystalline silicon doped with metals

Effects of electropositive (Au, Ag, Cu) and electronegative (Al, In) metal impurities are investigated from the viewpoint of photoluminescent and electronic properties of nanocrystalline silicon films prepared by laser ablation when depositing them onto a silicon substrate. Measured are time-resolved photoluminescence e. It was ascertained that only Au could essentially increase intensity and stability of photoluminescence, increase its relaxation time by three orders of magnitude as well as decrease the density of states near the film-substrate boundary. It has been shown that the metal impurities provide an essential effect on photovoltage arising in films of nanocrystalline Si as well as the capture of non-equilibrium electrons by traps both in films themselves and at the substrate boundary

Review of monograph

Review of monograph: A.A. Akopyan, O. Yu. Borkovskaya, N.L. Dmitruk, A.V. Karimov, R.V. Konakova, V.V. Melenin, A.V. Sachenko, M.N. Tursunov, D.M. Yodgorova. "Photoconverters with AlGaAs/GaAs Heterojunction on Textured GaAs Substrates (Physico-Technological aspects) -Fan Publishers, Tashkent, 200

The influence of size effects on thin films local piezoelectric response of thin films

We discuss the influence of size effects on the local piezoelectric response of thin films. In calculations of the electrostatic potential in the triple system “PFM probe tip – film – substrate,” the effective point charge model is used. The obtained expressions for the local piezoelectric response of a surface layer (film) capped are intended for the calculations of Piezoresponse Force Microscopy signals of thin polar films epitaxially grown on thick substrates. Theoretical predictions are in qualitative agreement with typical experimental results obtained for perovskite Pb(Zr, Ti)O₃ and multiferroic BiFeO₃ films

Emergence of the Russian Public Education System in the Patriarchal Era (1593-1721)

The paper explores the complicated path the emerging public education system took in the patriarchate period spanning from 1593 to 1721. It focuses on efforts to establish educational institutions in Russia and the role of the Orthodox Church as a protector of its flock from foreign religious influence. The materials used include works on the history of the public education system, created in Pre-Petrine Russia. The methodology of the research was based on the principles of historicism, system analysis and objectivity. With the scarce number of sources, we also widely utilized the descriptive method to rebuild as a complete picture of events as possible to show how the public education system evolved in Russia in the period from 1593 to 1721. As a summary, the authors point out that the emergence of public education in Russia's patriarchal period had distinctive features. According to the authors, these comprise attempts by the Orthodox Church to pioneer its own way in matters related to the preservation of the old world order. Maneuvering their way between Greeks and Latins, first centers of religious education in Russia suffered considerable harm, and the controversies caused the expulsion of the Likhud brothers from Moscow. In addition, as early as at the end of the patriarchal period, attempts were made to confer powers of a medieval inquisition on the Moscow Academy to combat dissent in the theological community