Study of a growth instability of γ-In[sub 2]Se[sub 3]

γ-In[sub 2]Se[sub 3] thin film are deposited for various substrate temperatures in the range of 523–673 K. This study shows that at 573 and 673 K the thin films are well crystallized with grains aligned along the c axis. Between these temperatures, a domain of instability appears where the γ-In[sub 2]Se[sub 3] thin films have a randomly orientation and the c-lattice parameter increases. The presence of the metastable phase κ-In[sub 2]Se[sub 3], during the growth, can explain the existence of this domain of instability. The insertion of Zn during the preparation process allows us to stabilize the phase κ at room temperature which confirms our hypothesis that the presence of κ-In[sub 2]Se[sub 3] perturbs the crystallization of γ-In[sub 2]Se[sub 3]. The increase of the c-lattice parameter can be explain by the fact that κ-In[sub 2]Se[sub 3] has a larger unit cell than γ-In[sub 2]Se[sub 3] or by a competition during the growth between the grains of both phases which could generate constraints along the c axis. During the cooling, the κ phase disappears in favor of the γ phase

On the ultrathin gold film used as buffer layer at the transparent conductive anode/organic electron donor interface

Previously, we have shown that a gold thin film of only 0.5 nm introduced at the interface between the indium tin oxide or ZnO anode and the organic electron donor in organic photovoltaic cells induces a strong improvement of the cell efficiency. Of course a thickness of 0.5 nm corresponds only to an averaged thickness, the films being too thin to be continuous. For a clear understanding of the physical mechanisms that are responsible for this improved behaviour, it is important to know the fractional coverage and the island height of this thin Au film. In the present work, we have used two different techniques, such as treated scanning electron microscope images and analysis of the inelastic part of peaks of X-ray photoelectron spectroscopy spectra, to estimate the gold coverage and island height of the transparent conductive anode. There is an excellent agreement between the results achieved by both methods. Only 15% of the anode is covered, which proves the high efficiency of gold as an anode buffer layer in organic photovoltaic devices

Hiding from the Moonlight: Luminosity and Temperature Affect Activity of Asian Nocturnal Primates in a Highly Seasonal Forest

The effect of moonlight and temperature on activity of slow lorises was previously little known and this knowledge might be useful for understanding many aspects of their behavioural ecology, and developing strategies to monitor and protect populations. In this study we aimed to determine if the activity of the pygmy loris (Nycticebus pygmaeus) is affected by ambient temperature and/or moonlight in a mixed deciduous forest. We radio-collared five females and five males in the Seima Protection Forest, Cambodia, in February to May, 2008 and January to March, 2009 and recorded their behaviour at 5 minutes intervals, totalling 2736 observations. We classified each observation as either inactive (sleeping or alert) or active behaviour (travel, feeding, grooming, or others). Moon luminosity (bright/dark) and ambient temperature were recorded for each observation. The response variable, activity, was binary (active or inactive), and a logit link function was used. Ambient temperature alone did not significantly affect mean activity. Although mean activity was significantly affected by moonlight, the interaction between moonlight and temperature was also significant: on bright nights, studied animals were increasingly more active with higher temperature; and on dark nights they were consistently active regardless of temperature. The most plausible explanation is that on bright cold nights the combined risk of being seen and attacked by predators and heat loss outweigh the benefit of active behaviours

Ngse au Point d'une technique d'obtention de couches minces texturées de MoSe2_2

A new process to obtain textured MoSe$_2$ thin films is described MoTe$_2$ thin films obtained by D.C. diode sputtering are annealed at 840 K during 24 h under Te and Se vapors. During the annealing MoSe$_2$ crystallites growths with their c axis perpendicular to the plane of the substrate. The evolution of the properties of the layers is investigated by X-Ray photoelectron spectroscopy (Y.PS), X-ray diffraction and scanning electron microscopy, the atomic ratio Se/Te is taken as parameter.Une technologie d'obtention de couches minces texturées de MoSe$_2$ a été mise au point. Ces couches sont obtenues à partir de couches de MoTe$_2$ déposées par pulvérisation diode continue, puis traitées thermiquement (recuit 24 h à 840 K) en présence de vapeur de Te et de Se, L'évolution des propriétés des couches, en fonction du rapport atomique Se/Te présent lors du recuit, est étudiée par spectroscopie de photoélectrons (XPS), diffraction de rayons X et microscopie à balayage

Grain boundary conductivity in different polycrystalline MoSe2_2 thin films

It has been shown early that curved plots for the conductivity of polycrystalline diselenide molybdenum were systematically obtained whatever the technique used for the obtention of the layers. In the general case of polycrystalline semiconductors these deviations from the simple thermoionic emission across the grain boundaries have been recently attributed to potential fluctuations at the grain boundaries. Here a good agreement between the experimental results and this new theory is obtained. The result deduced from theoretical propositions is conforted by the scanning electron micrographs of the layers and other preceeding experimental studies. In the light of the discussion of the MoSe$_2$ layers, a quality factor $Q$ is proposed for photovoltaic thin films. This estimation shows that the films obtained by solid state reaction and substitution are the best. Mo and Te thin films are sequentially deposited. Then an annealing under Se and Te pressure at 770 K for 24 h gives crystallized and stoichiometric MoSe$_2$ thin films. These films have the higher quality factor among the films studied here $(Q = 0.75)$. This is in close agreement with the good electrical and optical properties of these layers

Realization of tin oxide like anode for the manufacture of the organic solar cells

The transparent oxides such as SnO2, In2O3 and ZnO continue to arouse a private interest for their various applications. The objective of the various studies being to carry out the layers which are simultaneously most transparent and most conducting possible. Thus in the field of the solar spectrum, the transmission of the layers must be higher than 80% and their conductivity exceeding 103 (Ohm.cm)-1. Their transparency which is related to the value of their forbidden band must be higher than 3.7 e V. Their electric properties as for them depend on the composition of the layers and a possible doping. In this work, one characterized layers of SnO2 deposited by chemical pulverization, one carried out measurements by, electronic scan microscopy, diffraction of x-rays and also of the optical measurements and electronic. It results from it that the layers are conducting and transparent in the visible one but they are relatively rough, following its characterizations, one carried out organic photovoltaic cells using these layers of SnO2 and also of the commercial ITO like anode in these components. More particularly one was interested in the influence of the presence of a fine layer of gold between the anode and organic material

MS2 (M=W, Mo) Photosensitive thin films for solar cells

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MS2 (M=W, Mo) Photosensitive thin films for solar cells

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MS2 (M=W, Mo) Photosensitive thin films for solar cells

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