Вплив кристалічної об'ємної фракції на електронні властивості гідрогенізованого мікрокристалічного кремнію, дослідженого методом еліпсометрії та моделюванням мікроелектронних і фотонних структур

The main objective of the present work is to study experimentally and by simulation, using the one dimensional analysis of microelectronic and photonic structures program (AMPS-1D), the correlation between the crystalline volume fraction (Fc) and the transport properties of hydrogenated microcrystalline silicon thin films (мc-Si:H). The Fc was determined by spectroscopic ellipsometry (SE) and the electrical conductivity measurements. The мc-Si:H samples were deposited by radio-frequency magnetron sputtering technique of a crystalline silicon target, under an argon (Ar) gas mixture of 70 % of hydrogen (H2) and 30 % of Ar, at three different total pressures (2, 3 and 4 Pa) and changing substrate temperatures (25, 100, 150 and 200 °C). The dark conductivity was measured in a coplanar configuration in an optical cryostat under applied electrical field and controlling current with an electrometer. In the simulation studies of the dark conductivity using the AMPS-1D, we modelled the films as an alternation of amorphous and crystalline regions with different crystalline volume fractions Fc (from 0 to 80 %). The results evidently demonstrated that the conductivity depends on the width of the area separating amorphous and crystalline regions. We found a strong correlation between the c-Si:H films activation energy and the crystalline volume fraction where the grain size-to-thickness ratio plays a crucial role.Метою даної роботи є експериментальне і модельне дослідження кореляції між об'ємною фракцією кристалів і транспортними властивостями тонких плівок гідрогенізованого мікрокристалічного кремнію, використовуючи одновимірний аналіз програми мікроелектронних і фотонних структур (AMPS 1D). Об'ємну фракцію кристалів визначали спектроскопічною еліпсометрією і вимірюваннями елект- ропровідності. Зразки гідрогенізованого мікрокристалічного кремнію осаджували методом радіочастотного магнетронного розпилення кристалічної мішені кремнію у газовій суміші аргону і водню при трьох різних сумарних тисках (2, 3 і 4 Па) та змінюючи температуру підкладки (25, 100, 150 і 200 °С). Темна провідність вимірювалася в копланарній конфігурації в оптичному кріостаті при прикладанні електричного поля і керуючого струму. У дослідженнях темної провідності з використанням AMPS-1D ми моделювали плівки як чергування аморфних і кристалічних областей з різними кристалічними об'ємними фракціями (від 0 до 80 %). Результати показали, що провідність залежить від ширини ділянки, що розділяє аморфні та кристалічні області. Була виявлена сильна кореляція між енергією активації плівок гідрогенізованого мікрокристалічного кремнію і об'ємною часткою кристалічних речовин, де співвідношення розміру зерна до його товщини грає вирішальну роль

FTIR spectroscopic study of palygorskite: Influence of the composition of the octahedral sheet

The influence of chemical composition to position and intensity of the absorption bands observed in the FTIR spectra of palygorskite has been studied by a detailed comparative study of six samples. Palygorskites studied have high purity and different chemical composition. At one extreme, there are two samples that correspond to Mg-rich palygorskites, at the other extreme a sample with a composition very close to the theoretical formula of this mineral, and there are three further samples whose structural formulae lie between these extremes. The position of the bands identified in the FTIR spectra of the palygorskites studied is similar for all samples, but there are some differences in their intensity, which are significant. Analysing these intensities, valuable information about the distribution of cations along the octahedral sheet has been obtained. Isomorphic substitution in octahedral sheet occurs only in M2 position. Al, and Fe may occupy M2 position whereas Mg can occupy all possible sites: M1, M2 and M3

Conclusion: recommendations and findings of the RED SEED working group

RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters, and combines stakeholders from the remote sensing, modelling and response communities with experience in tracking volcanic effusive events. The group first met during a three day-long workshop held in Clermont Ferrand (France) between 28 and 30 May 2013. During each day, presentations were given reviewing the state of the art in terms of (a) volcano hot spot detection and parameterization, (b) operational satellite-based hot spot detection systems, (c) lava flow modelling and (d) response protocols during effusive crises. At the end of each presentation set, the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors, modellers and responders during an effusive crisis. The results of collating the final reports, and follow-up discussions that have been on-going since the workshop, are given here. We can reduce our discussions to four main findings. (1) Hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min. (2) Spectral radiance metrics can also be provided with high degrees of confidence. However, if we are to achieve a truly global system, more local receiving stations need to be installed with hot spot detection and data processing modules running on-site and in real time. (3) Models are operational, but need real-time input of reliable time-averaged discharge rate data and regular updates of digital elevation models if they are to be effective; the latter can be provided by the radar/photogrammetry community. (4) Information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities. All of this requires a sophisticated and centralized data collection, distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust. While the next chapter carries out an exercise to explore the viability of the last point, the detailed recommendations behind these findings are detailed here