Cu3BiS3 thin films were prepared on soda‐lime glass substrates by co‐evaporation of the precursors in a two‐step process; for that, the metallic precursors were evaporated from tungsten crucibles in the presence of elemental sulphur evaporated from a tantalum effusion cell. The films were characterized by spectral transmittance, Atomic Force Microscopy, X‐ray Photoelectron Spectroscopy, Scanning Electron Microscopy and electrical measurements to investigate the effect of growth conditions on the optical, morphological and electrical properties. The results revealed that the Cu3BiS3 films present p‐type conductivity, a high absorption coefficient (greater than 104 cm–1), and an energy band gap, Eg, of about 1.39 eV. We observed from Atomic Force Microscopy and electrical measurements that grain size and electric conductivity of the Cu3BiS3 samples are influenced by the copper mass ratio in this material. We found, in the high‐temperature range above room temperature, that carrier transport is thermally activated with activation energies fluctuating between 0.17 and 0.28 eV. This suggests that this compound has good properties to perform as absorbent layer in thin‐film solar cells. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Photonic crystals are some of the more spectacular realizations that periodic arrays can change the behavior of electromagnetic waves. In nature, so-called structural colors appear in insects and even plants. Some species create beautiful color patterns as part of biological behavior such as reproduction or defense mechanisms as a form of biomimetics. The interaction between light and matter occurs at the surface, producing diffraction, interference and reflectance, and light transmission is possible under suitable conditions. In particular, there are two Colombian butterflies, Morpho cypris and Greta oto, that exhibit iridescence phenomena on their wings, and in this work, we relate these phenomena to the photonic effect. The experimental and theoretical approaches of the optical response visible region were studied to understand the underlying mechanism behind the light-matter interaction on the wings of these Colombian butterflies. Our results can guide the design of novel devices that use iridescence as angular filters or even for cosmetic purposes. Nature is colored and attracts our attention due to its beauty and complex colors. Colors can be produced by pigmentation or by the arrangement of nanostructures. Recent studies showed that some species use this latter option to create beautiful color patterns as part of biological behavior such as reproduction or defense mechanisms as a form of mimicry 1-8 , and these tools have been perfected over millions of years in nature. In all cases, the interaction between light and matter occurs at the surface, producing diffraction, interference and reflectance phenomena. Additionally, light transmission is possible under suitable conditions. In the last decade, another optical phenomenon that has generated great interest among researchers is iridescence, which is related to the angular dependence of the observed color; there are many biological species and minerals that have this feature 9-11. In particular, there are two Colombian butterflies, Morpho cypris and Greta oto, that exhibit an iridescent effect on their wings. Iridescence has many feasible applications 12 , and a key advantage of structural colors over pigmented colors is the more intense coloration, especially under high light conditions. However, the physical interpretation of this phenomenon remains unclear and deserves more study. Iridescence is an effect that takes place in the visible spectrum 13,14 ; thus, the interaction of light with the surfaces of these systems implies the existence of nanostructures with sizes comparable to the wavelength in the visible region. On the other hand, there are man-made structures that exhibit iridescent effects, such as TiO 2 traces 15-17 , but total control over this property in man-made systems is not yet available. In this way, comprehension of the proper working conditions when light interacts with a butterfly's wings is a very important step toward man-made systems that will use this property. The Morpho cypris and Greta oto butterfly samples were provided, wit...

Boron-doped microcrystalline silicon films have been deposited in a plasma-enhanced chemical vapor deposition system using silane diluted in hydrogen, and diborane (B2H6) as a dopant gas. The temperature dependence of the dark conductivity has been measured from 120to420K in all samples. In the high-temperature range above room temperature, the carrier transport is found to be thermally activated, with a single activation energy that changes with the B2H6 compensation degree. In the low-temperature range (300–120K), variable range hopping (VRH) was established as a predominant electronic transport mechanism for all samples, with the exception of the sample with a diborane concentration of 12.5ppm. A model for Mott’s VRH, referred to as the “diffusional model,” which yields a relation between the conductivity and the localized density of gap states, is presented. Using classical equations from the percolation theory and the diffusional model, the density of states near the Fermi level, as well as the hopping parameters, are calculated. A correlation between the hopping parameters for both models is deduced. A numerical factor that improves the value of each parameter is calculated.

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We have carried out first-principles spin polarized calculations to obtain comprehensive information regarding the structural, magnetic, and electronic properties of the Mn-doped GaSb compound with dopant concentrations: x = 0.062, 0.083, 0.125, 0.25, and 0.50. The plane-wave pseudopotential method was used in order to calculate total energies and electronic structures. It was found that the MnGa substitution is the most stable configuration with a formation energy of ∼1.60 eV/Mn-atom. The calculated density of states shows that the half-metallic ferromagnetism is energetically stable for all dopant concentrations with a total magnetization of about 4.0 μB/Mn-atom. The results indicate that the magnetic ground state originates from the strong hybridization between Mn-d and Sb-p states, which agree with previous studies on Mn-doped wide gap semiconductors. This study gives new clues to the fabrication of diluted magnetic semiconductors.

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