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Sebkha Imlili (Atlantic Sahara) is a salt flat with over 160 permanent holes of hypersaline water generated in the Holocene and inhabited by euryhaline organisms that are considered to be relics of the past, including the cichlid fish Coptodon guineensis. We surveyed the fish parasites four times over one year, to i) identify the parasites, and ii) determine possible seasonality in infection patterns. Over 60% of the fish were infected by one to three helminths: an acanthocephalan in the intestine and two digenean metacercariae in the kidney, spleen, liver, muscle, and mesenteries. The acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae was identified morphologically and molecularly; only one digenean (the heterophyid Pygidiopsis genata) could be identified molecularly. Both identified parasites were present throughout the sampling periods; the unidentified metacercariae were present only in summer and fall. Mean intensities, but not prevalence of infection by the acanthocephalan, reflected a biannual pattern of transmission. Infection accrued with fish size, possibly due to cannibalism. Because the water holes include only a few invertebrates, the intermediate hosts of these parasites can be inferred to be the gastropod Ecrobia ventrosa for the digeneans and either the copepod Cletocamtpus retrogressus or the ostracod Cyprideis torosa for the acanthocephalan. This ecosystem appears stable and provides a window into the past, as the acanthocephalan likely switched from freshwater tilapia to C. guineensis when the Sebkha formed. However, this is a vulnerable environment where the survival of these parasites depends on interactions maintained among only very few hosts.

In this paper, thin films of Ag2ZnSnS4 (AZTS) were spin-coated on to ordinary glass substrates and annealed at temperatures ranging from 300 to 375 °C without sulfurization. Characterization techniques like X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Raman Spectroscopy (RS), Energy Dispersive X-ray Spectroscopy (EDS), and UV-Vis spectrophotometry were used to investigate the different physical properties of AZTS thin films. The analyses of XRD and Raman patterns showed that AZTS thin films have a polycrystalline structure with peaks corresponding to the pure tetragonal phase. SEM micrographs showed a nearly uniform, dense, and compact surface morphology for AZTS thin film annealed at 375 °C. The films showed absorption coefficients greater than 104 cm−1 with band gaps found between 1.50 and 1.59 eV. These properties make AZTS thin films a suitable absorber layer for photovoltaic applications. Highlights: Synthesis and characterization of Ag2ZnSnS4 thin films by sol-gel method associated to spin coating technique. Study the effect of annealing temperature on some physical properties. XRD data and Raman scattering measurements indicated the formation of pure Ag2ZnSnS4. Compositional and morphological show that Ag2ZnSnS4 thin films can be suitable for photovoltaic applications. [ABSTRACT FROM AUTHOR]

Our TiO2 thin films were elaborated using spray pyrolysis technique. The spray solutions were prepared by two titanium precursors: titanium (IV) propoxide and titanium chloride. The elaborated thin films were analyzed with different characterization techniques such as X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV–visible spectroscopy. These characterizations showed that the change of precursors from titanium chloride to titanium propoxide has a significant impact on all TiO2 properties. The structural characterizations showed the formation of anatase TiO2 and the crystallization improvement when the precursor changed from titanium chloride to titanium (IV) propoxide, which proves the superiority of our TiO2 thin layers made without any type of annealing in comparison with other previous studies. The SEM images showed an improvement of the surface quality of the TiO2 thin layers with the change of TiO2 precursors' solution. The obtained optical properties confirmed the semiconducting properties of TiO2 prepared by titanium propoxide with a large band gap equal to 3.28 eV and shifted to 3.18 eV. The refractive index increases from ~1.75 to ~2.14, while the porosity decreases. To confirm the experimental results, the Wien2K code, founded on the full‐potential linearized augmented plane wave (FP‐LAPW), has been used. The theoretical study has been done by applying the generalized gradient approximation (GGA), the modified Beck‐Johnson (MBJ) exchange potential, and the local spin density approximation + Hubbard's parameter U (LSDA + U). The theoretical results varied with the variation of approximations. The obtained properties were improved with LSDA + U and acquired the real values of Eg, n, and k for anatase TiO2 (like Eg = 3.214 eV). The obtained experimental and theoretical results could be considered superposable or better than other ones recently published. [ABSTRACT FROM AUTHOR]

In this work, we study the thermal behavior of end-of-range (EOR) defects formed in Ge+ (35 KeV, 1 × 1015 cm−2) pre-amorphized silicon at room temperature. Using low-temperature photoluminescence (PL) and transmission electron microscopy (TEM) in weak-beam dark-field (WBDF) mode, we show that, EOR defects, formed just beneath the former crystal to amorphous (c/a) interface, manifest several configurations depending on the thermal budget. For samples annealed at low thermal budget, PL measurements show that EOR defects consist only of various nano-self-interstitial clusters. However, during a middle annealing budget, there is appearance of {113} defects in addition to clusters. At a critical high thermal budget, the plan-view WBDF micrographs reveal that {113} defects are transformed into dislocation loops (DL). After that, as the annealing progresses, the different types of EOR defects grow in size, where their density decreases and their structure changes. This thermal behavior of EOR defects can be explained by the Ostwald ripening mechanism. [ABSTRACT FROM AUTHOR]

In this study, semiconductor compound Cu2BaSnS4 absorber layer thin films were elaborated by the sol–gel approach associated with dip-coating deposition technique at different dipping speeds. The influence of dipping speed at different speeds of 30 mm/min, 40 mm/min, 50 mm/min, 60 mm/min and 70 mm/min, respectively, on different properties of elaborated films was investigated. X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), UV–vis spectrophotometry and four-point probe technique were employed to analyze the structural, compositional, morphological, optical and electrical properties. XRD measurements proved the formation of trigonal Cu2BaSnS4 with privileged orientation along the (100) plane. It was seen that crystallites' size of trigonal CBaTS thin films increased with the dipping speed increased from 27.93 to 41.91 nm. Secondary phase BaS2 was observed with CBaTS phase in all films. Raman spectroscopy measurements confirmed the presence of CBaTS films by the Raman peak located at 341 cm−1. EDS analyses confirmed the existence of elements composition present in CBaTS thin films. SEM micrographs showed the increase in uniformity and density of films. Also, the best surface morphology was observed at the film deposited at 70 mm/min. UV–vis spectrophotometry showed that the absorption coefficients are greater than 104 cm−1. Optical band gap of CBaTS thin films decreased from 1.61 to 1.5 eV when the dipping speed increased. The calculated electrical conductivity of CBaTS thin films was found in the range of 0.11–16.66 (Ω. cm) - 1 . These properties are interesting and show that Cu2BaSnS4 thin films can be used as a good absorber in thin film-based solar cells. [ABSTRACT FROM AUTHOR]

Semiconductor compounds Cu2MnSnS4 absorbers materials were synthesis by the sol–gel approach and deposited using dip-coating technique on ordinary glass substrates. In this work, we have studied the effect of various annealing temperature such as: 400 °C, 425 °C, 450 °C and 475 °C for 1 min on the structural, compositional, morphological, optical and electrical investigations. CMnTS thin films have been characterized by some analyse techniques such as: X-ray diffractometer (XRD), Raman spectroscopy, dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), UV–visible spectroscopy and four-point probe method. XRD data proved the formation of stannite Cu2MnSnS4 with privileged direction at (112) plane. Crystallite size of stannite CMnTS thin films increased with the increase of annealing temperature from 7.26 to 11.57 nm with annealing temperature augmented. Raman experiments complete the confirmation of stannite CMnTS thin films existence by Raman vibrational modes located at 288 cm−1 and 330 cm−1. EDS analysis demonstrated close-stoichiometry of CMnTS thin films annealed at 450 and 475 °C. SEM images demonstrated the improvement of crystallinity and uniformity of surface morphologies when annealing temperature is 475 °C. UV–visible spectroscopy indicated that the transmittance spectra increased when annealing temperature increased in the wavelength range of 450–850 nm. The absorption coefficient values are higher than 104 cm−1, the approximated bandgap of CMnTS absorber material decrease in the range of 1.72–1.5 eV when annealing temperature increased. The electrical resistivity of CMnTS thin films decrease from 4.77 to 0.85 (Ω.cm). These properties are appropriate for photovoltaic solar cells applications. [ABSTRACT FROM AUTHOR]

Quaternary semiconductor Cu2ZnSnS4 absorber material was synthesized by the sol-gel method deposited by the dip-coating technique on ordinary glass substrates. In this study, we have investigated the effects of dip-coating cycle at different cycles: 2, 4 and 6, and annealing temperature at various temperatures: 300, 325 and 375 °C on the structural, morphological compositional, optical and electrical properties. The films have been characterized by different characterization techniques such as X-ray diffractometer (XRD), Raman scattering experiments, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), UV–visible spectrophotometer and four-point probe method. XRD patterns indicated kesterite CZTS with preferential orientation along (112) plane, Cu2-xS, SnS2 and SnS secondary phases were observed with CZTS phase in some samples. The pure CZTS phase was formed for the sample annealed at 375 °C and sample deposited at 2 cycles. Raman spectroscopy confirmed the presence of CZTS thin films in all samples using Raman characteristic peak at 332 cm−1. EDS analysis showed near-stoichiometric CZTS thin films. (SEM) images showed the uniform and dense surfaces morphologies. The gap energy is estimated from absorbance data by using absorption spectra fitting (ASF). The optical band gap decreases with the increasing of dip-coating cycle in the range of 1.33–1.44 ∓ 0.01 eV and also increases with the increasing of annealing temperature in the range of 1.38–1.47 ∓ 0.01 eV. The electrical sheet resistance increased from 2.60 ∓ 0.01 to 4.67 ∓ 0.01 × 103 (Ω/square) when the annealing temperature increased and decreased when the dip-coating cycle increased in range of 0.99 ∓ 0.01 and 1.19 ∓ 0.01 × 103 (Ω/square). These characteristics are suitable for solar cells applications. [ABSTRACT FROM AUTHOR]

This paper presents the optimal configuration of parameters for the elaborated Cu2ZnSnS4 (CZTS) absorber layer, using the sol–gel method associated with dip-coating technique on ordinary glass substrates. Taguchi design of experiments with L27 (38) orthogonal array, a signal-to-noise (S/N) ratio, and an analysis of variance (ANOVA) were used to determine the best optical properties for photovoltaic applications (optical bandgap energy) of CZTS thin films. Eight factors named annealing temperature, Cu/(Zn+Sn) ratio, Zn/Sn ratio, S/metal ratio, number of pre-annealing and dip coating, dip-coating cycle, annealing time, and dip-coating speed were chosen. To conduct the tests, we apply Taguchi method; three levels were fixed for each factor. The most important factors of the deposition approach on the optical properties of the fixed as-synthesized CZTS films were determined. The analysis of the obtained results indicated that the important parameters are the Zn/Sn ratio and annealing temperature in air by employing Taguchi approach. A validation test is also carried out to check whether the found optimal combinations of the parameter are correct. CZTS thin-film synthesis with optimal conditions has been characterized, using an X-ray diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), UV–visible spectrophotometer, and four-point probe method. XRD data show a kesterite structure with a preferential orientation along the (112) plan; UV–visible spectrophotometer indicated that the bandgap energy of the CZTS thin film is 1.51 eV and a cross section showed the suitable film thickness in the order of ~1.80 µm. Highlights: Synthesis of CZTS thin films by sol gel associated to the dip-coating technique. Application of Taguchi method to optimize the sol gel dip-coating process of the semiconductor CZTS with good optical properties. The statistical analysis (ANOVA) has the capacity to give information about certain statistical parameters. The CZTS thin film elaborated with optimal parameters has good morphological optical and electrical properties. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the influence of the Ge content on the {113} defects formed, after a (35 keV, 1 × 1015 Ge+/cm2) preamorphization step followed by annealing at 680 °C, in relaxed SiGe alloys. For that, plan-view Transmission Electron Microscopy (PTEM) under appropriate imaging conditions was used to study the {113} defects evolution as a function of the Ge content. Experimental results show that, increasing the Ge content results in a net reduction of both the density and the size of the {113} defects. Results analysis was performed in the framework of the 'excess interstitials' model which describes perfectly the observed decrease of the {113} defects density in Si. Moreover, through a confrontation between the TEM observations and the predictions of this model, we show that the density of the interstitials contained in the defects (deduced from PTEM images) is a quasi linear function of the density of excess interstitials generated during the preamorphization step beneath the c/a interface, as calculated by the SRIM code. We conclude that collisional arguments can appropriately explain the observed evolution of the {113} defects density as a function of the Ge content. Meanwhile, the observed reduction of the {113} defects size with the Ge content, may be ascribed to a decrease of the transport capacity DiCi*, responsible for the defects growth. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]