Класифікація мультикутової та спектральної еліпсометрії для напівпровідникових наноструктур

Досліджені можливості багатопараметричного визначення напівпровідникових наноструктур на основі спектральних залежностей поляризованого випромінювання коефіцієнта відбиття Rp, Rs від кута падіння в діапазоні 200-800 нм. Експериментальні дані показали високі коефіцієнти чутливості відбивання кутової залежності від типу полікристалічних структур. Наявність додаткових спектральних екстремумів в залежності від заломлення і поглинання може бути пов'язане з розміром зерен по- лікристалічної структури і типу меж зерен. Показана можливість багатопараметричного дослідження. оптичних властивостей і товщини напівпровідникових шарів на кремнієвій підкладці. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/35955Исследованы возможности многопараметрического определения полупроводниковых нанострук- тур на основе спектральных зависимостей поляризованного излучения коэффициента отражения Rp, Rs от угла падения в диапазоне 200-800 нм. Экспериментальные данные показали высокие коэффициенты чувствительности отражения угловой зависимости от типа поликристаллических структур. Наличие дополнительных спектральных экстремумов в зависимости от преломления и поглощения может быть связано с размером зерен поликристаллической структуры и типа границ зерен. Показана возможность многопараметрического исследования оптических свойств и толщины полупроводниковых слоев на кремниевой подложке. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/35955The possibilities of multiparameter determination of semiconductor nanostructures based on spectral dependencies of polarized radiation reflection coefficient Rp, Rs on the incidence angle in the range of 200- 800 nm are investigated. Experimental data have shown high sensitivity of reflection coefficients angular dependence to the type of polycrystalline structures at the same film thickness. The presence of additional extremums in spectral dependence of refraction and absorption indexes is detected; this could be connected with grain size of polycrystalline structure and type of grain boundaries. The possibility of multiparameter optical research of properties and thickness of semiconductor layers on Si substrate is shown. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3595

Higher mass-independent isotope fractionation of methylmercury in the pelagic food web of Lake Baikal (Russia)

cited By 36International audienceMercury undergoes several transformations that influence its stable isotope composition during a number of environmental and biological processes. Measurements of Hg isotopic mass-dependent (MDF) and mass-independent fractionation (MIF) in food webs may therefore help to identify major sources and processes leading to significant bioaccumulation of methylmercury (MeHg). In this work, δ13C, δ15N, concentration of Hg species (MeHg, inorganic Hg), and stable isotopic composition of Hg were determined at different trophic levels of the remote and pristine Lake Baikal ecosystem. Muscle of seals and different fish as well as amphipods, zooplankton, and phytoplankton were specifically investigated. MDF during trophic transfer of MeHg leading to enrichment of heavier isotopes in the predators was clearly established by δ202Hg measurements in the pelagic prey-predator system (carnivorous sculpins and top-predator seals). Despite the low concentrations of Hg in the ecosystem, the pelagic food web reveals very high MIF Δ199Hg (3.15-6.65‰) in comparison to coastal fish (0.26-1.65‰) and most previous studies in aquatic organisms. Trophic transfer does not influence MIF signature since similar Δ199Hg was observed in sculpins (4.59 ± 0.55‰) and seal muscles (4.62 ± 0.60‰). The MIF is suggested to be mainly controlled by specific physical and biogeochemical characteristics of the water column. The higher level of MIF in pelagic fish of Lake Baikal is mainly due to the bioaccumulation of residual MeHg that is efficiently turned over and photodemethylated in deep oligotrophic and stationary (i.e., long residence time) freshwater columns. © 2012 American Chemical Society

Natural Hg isotopic composition of different Hg compounds in mammal tissues as a proxy for in vivo breakdown of toxic methylmercury

International audienceIn the last decade, specific attention has been paid to total mercury (HgT) stable isotopic composition, especially in natural samples such as aquatic organisms, due to its potential to track the cycle of this toxic element in the environment. Here, we investigated Hg Compound Specific stable Isotopic Composition (CSIC) of natural inorganic Hg (iHg) and methylmercury (MMHg) in various tissues of aquatic mammals (Beluga whale from the Arctic marine environment and seals from the freshwater lake Baikal, Russia). In seals' organs the variation in mass dependent fractionation (MDF, δ202Hg) for total Hg was significantly correlated to the respective fraction of iHg and MMHg compounds, with MMHg being enriched by ∼3‰ in heavier isotopes relative to iHg. On the other hand, we observe insignificant variation in Hg mass independent isotope fractionation (MIF, Δ199Hg) among iHg and MMHg in all organs for the same mammal species and MMHg in prey items. MIF signatures suggest that both MMHg and iHg in aquatic mammals have the same origin (i.e., MMHg from food), and are representative of Hg photochemistry in the water column of the mammal ecosystem. MDF signatures of Hg compounds indicate that MMHg is demethylated in vivo before being stored in the muscle, and the iHg formed is stored in the liver, and to a lesser extent in the kidney, before excretion. Thus, Hg CSIC analysis in mammals can be a powerful tool for tracing the metabolic response to Hg exposur