Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Nonmonotone projected gradient techniques are considered for the minimization of differentiable functions on closed convex sets. The classical projected gradient schemes are extended to include a nonmonotone steplength strategy that is based on the Grippo--Lampariello--Lucidi nonmonotone line search. In particular, the nonmonotone strategy is combined with the spectral gradient choice of steplength to accelerate the convergence process. In addition to the classical projected gradient nonlinear path, the feasible spectral projected gradient is used as a search direction to avoid additional trial projections during the one-dimensional search process. Convergence properties and extensive numerical results are presented.

/pdf/nonmonotone-spectral-projected-gradient-methods-on-convex-1tesp83age.pdf

Nonmonotone Spectral Projected Gradient Methods on Convex Sets

Graphene’s success has shown not only that it is possible to create stable, single-atom-thick sheets from a crystalline solid but that these materials have fundamentally different properties than the parent material. We have synthesized for the first time, millimeter-scale crystals of a hydrogen-terminated germanium multilayered graphane analogue (germanane, GeH) from the topochemical deintercalation of CaGe2. This layered van der Waals solid is analogous to multilayered graphane (CH). The surface layer of GeH only slowly oxidizes in air over the span of 5 months, while the underlying layers are resilient to oxidation based on X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy measurements. The GeH is thermally stable up to 75 °C; however, above this temperature amorphization and dehydrogenation begin to occur. These sheets can be mechanically exfoliated as single and few layers onto SiO2/Si surfaces. This material represents a new class of covalently terminated graphane analogue...

/pdf/stability-and-exfoliation-of-germanane-a-germanium-graphane-53g844s792.pdf

Stability and Exfoliation of Germanane: A Germanium Graphane Analogue

Solar power generation by PV (photovoltaic) technology: A review

The first use of non-centrosymmetric Janus Au-TiO(2) photocatalysts in efficient, plasmon-enhanced visible-light hydrogen generation is demonstrated. The intense localization of plasmonic near-fields close to the Au-TiO(2) interface, coupled with optical transitions involving localized electronic states in amorphous TiO(2) brings about enhanced optical absorption and the generation of electron-hole pairs for photocatalysis.

Janus Au-TiO2 photocatalysts with strong localization of plasmonic near-fields for efficient visible-light hydrogen generation.

https://www.ime.usp.br/~egbirgin/publications/bcm.pdf

Estimation of the Optical Constants and the Thickness of Thin Films Using Unconstrained Optimization

In this work the relationship between the characteristic energy of the Urbach edge ${E}_{0}$ and the parameter ${B}^{\frac{1}{2}}$ of the Tauc's representation of the absorption coefficient of $a$-SiN- and $a$-GeN-based alloys is presented and discussed. No correspondence has been experimentally found between ${B}^{\frac{1}{2}}$ and the topological disorder induced by small impurity concentrations in the network (less than a few at.%), which provokes a broadening of the Urbach tail. In the alloy regime, nevertheless, ${E}_{0}$ and ${B}^{\frac{1}{2}}$ present a linear correspondence. This fact is discussed in terms of the structural changes induced by atoms of different atomic coordination, i.e., on the base of the dominant bonding character (which changes from purely covalent to partially ionic) and the electronic states at the top of the valence band, as the nitrogen content is increased. The effects of hydrogen, carbon, and silicon in the $a$-Si and $a$-Ge networks are also discussed in terms of the Tauc slope ${B}^{\frac{1}{2}}$ parameter.

Absorption edge, band tails, and disorder of amorphous semiconductors

The known properties of nitrogen as an impurity in, and as an alloy element of, the germanium network are reviewed in this article. Amorphous and crystalline germanium–nitrogen alloys are interesting materials with potential applications for protective coatings and window layers for solar conversion devices. They may also act as effective diffusion masks for III-V electronic devices. The existing data are compared with similar properties of other group IV nitrides, in particular with silicon nitride. To a certain extent, the general picture mirrors the one found in Si–N systems, as expected from the similar valence structure of both elemental semiconductors. However, important differences appear in the deposition methods and alloy composition, the optical properties of as grown films, and the electrical behavior of nitrogen-doped amorphous layers. Structural studies are reviewed, including band structure calculations and the energies of nitrogen-related defects, which are compared with experimental data. ...

Nitrogen in germanium

This work presents the application of a recently developed numerical method to determine the thickness and the optical constants of thin films using experimental transmittance data only. This method may be applied to films not displaying a fringe pattern and is shown to work for a-Si:H (hydrogenated amorphous silicon) layers as thin as 100 nm. The performance and limitations of the method are discussed on the basis of experiments performed on a series of six a-Si:H samples grown under identical conditions, but with thickness varying from 98 nm to 1.2 μm.

/pdf/determination-of-thickness-and-optical-constants-of-h7bwzxcc8w.pdf

Determination of thickness and optical constants of amorphous silicon films from transmittance data

We discuss a new method to estimate the absorption coefficient, the index of refraction, and the thickness of thin films using optical transmission data only. To solve the problem we used a pointwise constrained optimization approach, defining a nonlinear programming problem, the unknowns of which are the coefficients to be estimated, with linear constraints that represent prior knowledge about the physical solution. The method applies to all kinds of transmission spectra and does not rely on the existence of fringe patterns or transparency. Results on amorphous semiconductor thin films and gedanken films are reported. They show that the new method is highly reliable.

I. Chambouleyron

Papers

Estimation of the Optical Constants and the Thickness of Thin Films Using Unconstrained Optimization

Absorption edge, band tails, and disorder of amorphous semiconductors

Nitrogen in germanium

Determination of thickness and optical constants of amorphous silicon films from transmittance data

Retrieval of optical constants and thickness of thin films from transmission spectra