Models of the adsorbtion-catalytic centers on transition metals

The models of adsorbo-catalitic centers for transition metals, which use the peculiarities of the electron-orbital structures as insulated and bounded atoms, have been analized. The important role of the unfilled d-orbitals, their orientation, changing of the occupation of d-shalls, and influence of the ligands with completely occupied d-orbitals were considered in connection with the catalytic activity of the transient metals. The new approach for enhanced catalytic properties, based on the film alloys of catalytic metals, was proposed.Проаналізовано моделі адсорбо-каталітичних центрів перехідних металів, враховуючи електронні орбіталі як ізольованих, так і сконденсованих у тверде тіло атомів. Відзначається домінуючий вплив на каталітичну активність незаповнених d -оболонок. Запропоновано новий підхід для підвищення каталітичної активності, що базується на використанні плівкових сплавів перехідних металів

Electron-hole Fermi liquid in nanosized semiconductor structures

The experimental and theoretical results on the quantum-sized electron-hole liquid plasma (EHLP) in semiconductors and analysis of the difference of it in comparison to the bulk one have been presented. The non-equilibrium Fermi EHLP can be created in the bulk and layered structures (insulator-semiconductor interfaces, thin films, quantum superlattices, etc.) at low temperatures and powerful laser radiation. In the quantum-sized structures, however, these phenomena appear at much higher temperatures, up to the room ones. The peculiarities of EHLP phenomena are: (1) appearance the very broad luminescence line in the low-energy side of its spectrum, which have constant width and energy position under variation of the light intensity as well as narrowing peak when increasing the temperature; (2) appearance of stimulated radiation with a relatively low excitation threshold (the so-called “surface laser effect”); (3) planar ballistic expansion of electron-hole plasma over long distances; (4) predicted effect of transformation of non-equilibrium 2D plasmons into radiative modes

Electron-hole Fermi liquid in nanosized semiconductor structures

The experimental and theoretical results on the quantum-sized electron-hole liquid plasma (EHLP) in semiconductors and analysis of the difference of it in comparison to the bulk one have been presented. The non-equilibrium Fermi EHLP can be created in the bulk and layered structures (insulator-semiconductor interfaces, thin films, quantum superlattices, etc.) at low temperatures and powerful laser radiation. In the quantum-sized structures, however, these phenomena appear at much higher temperatures, up to the room ones. The peculiarities of EHLP phenomena are: (1) appearance the very broad luminescence line in the low-energy side of its spectrum, which have constant width and energy position under variation of the light intensity as well as narrowing peak when increasing the temperature; (2) appearance of stimulated radiation with a relatively low excitation threshold (the so-called “surface laser effect”); (3) planar ballistic expansion of electron-hole plasma over long distances; (4) predicted effect of transformation of non-equilibrium 2D plasmons into radiative modes

The enhanced catalytic dissociation of adsorbed hydrogen containing molecules

Some general conceptions and mechanisms of dissociative adsorption and catalysis are analyzed. The role of such factors as electronic shell configurations of isolated atoms, crystalline structure of the surface, local structural irregularities and defects, orientation of the surface bonds, dimensional effects, the presence of foreign atoms in the local atomic environment as well as the local symmetry of adsorption center are discussed. These considerations were used in developing the program for computer simulation of the process. The catalytic properties of PdCux surface alloys are analyzed using computer modelling and thus the enhancement of dissociative adsorption of H₂ for such a system is predicted. The experimental data, demonstrating the enhancement of sensitivity of MIS sensor with CuPd electrode in comparison with the pure Pd electrode, are presented.Аналізуються деякі загальні концепції і механізми дисоціативної адсорбції і каталізу. Обговорюється роль таких факторів, як конфігурації електронних оболонок ізольованих атомів, кристалічна структура поверхні, локальні структурні нерегулярності, орієнтація поверхневих зв’язків, ефекти розмірності, присутність чужорідних атомів у локальному атомному оточенні, а також роль локальної симетрії центра адсорбції. Ці обговорення використовуються при розвитку програми для комп’ютерного моделювання процесу. Каталітичні властивості поверхневих сплавів PdCux аналізуються, використовуючи комп’ютерне моделювання, і отже, передбачено підсилення дисоціативної адсорбції H₂ для такої системи. Представлені експериментальні дані, які демонструють підсилення чутливості сенсора метал-ізолятор-напівпровідник з електродом CuPd у порівнянні з чистим електродом Pd

Mechanism of Oxygen Redistribution During Ultra-shallow Junction Formation in Silicon

The transport of dissolved oxygen in the Czochralski silicon towards the arsenic-doped ultra-shallow junction was investigated. Ultra-shallow junction was formed by low-energy As+ ion implantation with the subsequent furnace annealing at 750 C-950 C temperatures for the dopant activation. Oxygen and arse-nic redistributions were investigated by secondary ion mass spectrometry (SIMS) technique. The peculiari-ties of defect creation and transformation were studied by the X-ray diffuse scattering technique (XDS). It was found that oxygen concentration in the arsenic redistribution region is increased a few times already after 1 minute of annealing. Increase of annealing time leads to decrease of oxygen accumulation as a re-sult of oxygen transportation to the SiO2/Si interface. As a result the thickness of screen silicon oxide is in-creased by 0.5 nm. This effect is related with the oxygen gettering from the wafer bulk. A physical mecha-nism of the oxygen transfer is discussed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3527

Optical properties of diamond-like carbon films subjected to ultraviolet irradiation

Influence of UV irradiation on optical properties of the nitrogen doped diamond-like carbon (DLC) films was studied. Transparency spectra of the initial, UV irradiated and concentrated UV irradiated films were measured. Dependences of the optical bandgap on the nitrogen content were obtained from these spectra. Raman measurements revealed a decrease in the graphitic cluster size by two times after UV irradiation. It was shown that concentrated UV irradiation leads to smaller changes in comparison with nonconcentrated UV. Physical mechanism of air oxygen embedding into the DLC structure under UV irradiation is proposed to explain the changes in the properties of the films

Instability of homogeneous composition of highly strained quantum wells in heterostructures GaAs/InxGa₁₋xAs/GaAs

InxGa₁-xAs QW-layers embedded in GaAs matrix have been characterized by photoluminescence (PL). The relation between the PL parameters and mismatch of the lattice parameters of the layer and matrix was established. In highly strained layers several PL bands were observed instead one band. This is probably a result of alternating content of In raised only in highly strained layers

Formation of silicon nanoclusters in buried ultra-thin oxide layers

The peculiarities of buried layer formation obtained by co-implantation of O2 ions with the energy of 130 keV and carbon ions within the energy range of 30-50 keV have been investigated. The corresponding ion doses for carbon and oxygen ions were equal to 2 x 10¹⁶ cm⁻² and 1.8 x 10¹⁷ cm⁻², respectively. It has been observed that annealing at 1150 °C results in enhanced oxygen diffusion towards the region with a maximum carbon concentration. Analysis of X-ray diffraction patterns with a SIMS depth profiles inherent to annealed samples suggests formation of Si nanoclusters in the region with maximum concentrations of carbon and oxygen vacancies. The intensive luminescence has been observed with the maximum at 600 nm, which could be associated with silicon nano-inclusions in thin stoichiometric SiO₂ layer

Optimization of technology for fabrication of sectional nuclear radiation detectors based on high-resistance silicon

On the basis of experimental studies the surface-barrier technology for fabrication of sectional nuclear radiation detectors with using of the high-resistance n-Si plates of large diameter (~ 100 mm) was optimized. The 9-sectional detector matrixes were manufactured. In such matrix each section is a separate detector with the thickness of sensitive area W ≤ 350 μm, the working area S = 4 cm², and the energy resolution R = 50…75 keV under irradiation by three-component α-source. The electrophysical and spectrometric characteristics of the sectional silicon detectors were determined. The manufactured detectors can be used in the nuclear experiments involving heavy ions at the low yields of reaction products.На основі проведених експериментальних досліджень оптимізовано поверхнево-бар'єрну технологію виготовлення секційних детекторів ядерних випромінювань з використанням пластин високоомного n-Si великого діаметра (~ 100 мм). Виготовлено 9-секційні детекторні матриці, де кожна секція є окремим детектором з товщиною чутливої області W ≤ 350 мкм, робочою площею S = 4 см² та енергетичною роздільною здатністю R = 50…75 кеВ при опроміненні трикомпонентним α-джерелом. Визначено електрофізичні та спектрометричні характеристики секційних кремнієвих детекторів. Виготовлені детектори можуть бути використані в ядерних експериментах за участю важких іонів при низьких виходах продуктів реакцій.На основе проведенных экспериментальных исследований оптимизирована поверхностно-барьерная технология изготовления секционных детекторов ядерных излучений с использованием пластин высокоомного n-Si большого диаметра (~ 100 мм). Изготовлены 9-секционные детекторные матрицы, где каждая секция является отдельным детектором с толщиной чувствительной области W ≤ 350 мкм, рабочей площадью S = 4 см² и энергетическим разрешением R = 50…75 кэВ при облучении трехкомпонентным α-источником. Определены электрофизические и спектрометрические характеристики секционных кремниевых детекторов. Изготовленные детекторы могут быть использованы в ядерных экспериментах с участием тяжелых ионов при низких выходах продуктов реакций

The study of solar cells with back side contacts at low illumination

Theoretical analysis and experimental research of Si solar cells (SC) with interdigitated back side contacts (BSC) photovoltaic parameters and photoconversion efficiency at low light level have been done in presence of floating p⁺-n junctions and isotype n⁺-n junctions on frontal (illuminated) surface. It has been found that in case of floating junction the magnitudes of short-circuit current, open-circuit voltage and efficiency, as well as of internal quantum efficiency of photocurrent can decrease significantly due to recombination in the space charge region (SCR) rather than to surface recombination. In case of isotype junction, this decrease is absent. These results allow to conclude that the floating p⁺-n junctions at the front surface of the silicon BSC SC would be appropriate for use only in case of an illumination intensity ≥ 1000 W/m²