Thin films of arsenic sulfide by chemical deposition and formation of InAs

We report a method for obtaining thin films of arsenic sulfide by chemical bath deposition and the subsequent formation of InAs by heating the films with a vacuum-deposited coating of In. X-ray diffraction (XRD) studies have shown that the thin film deposited from chemical baths of pH ∼2, prepared by mixing aqueous acidic solutions of As(III) with sodium thiosulfate, is a composite film of crystalline As2O3 and As2S3, with the incorporation of sulfur. When heated at 150–250 ◦C, the As2O3 component transforms to As2S3, but still with very few identifiable peaks in the XRD patterns of the annealed samples. The films have a direct band gap of ≈2.7 eV (as-prepared) and ≈2.52 eV (heated at 250 ◦C), with forbidden optical transitions. The sheet resistance of the film (300 nm thick) is 1012 Ω, and the electrical conductivity is 10−8 Ω−1 cm−1. After being heated in a sulfur-rich atmosphere at >200 ◦C, the films show photosensitivity. The As2O3/As2S3 thin film with an evaporated indium film, when heated at 250 ◦C in nitrogen or air, produces InAs as a major crystalline component. In this case, In2S3 or In2O3 may be present as a minor component in the films, depending on whether heating is done in nitrogen or air, respectively. The optical band gap of this InAs component is direct, 0.5 to 0.8 eV, depending on the film thickness and heating process. These composite films are photosensitive; a dark conductivity of 0.05 Ω−1 cm−1 in the films formed in nitrogen is ascribed to InAs and 5 Ω−1 cm−1 in the films formed by heating in air is ascribed to the In2O3 component. The photoconductivity of the films is of the same order of magnitude as the dark conductivity in each case

Ferromagnetismo en manganitas sustituidas con plata de estructura perovskita.

Se prepararon por primera vez una serie de óxidos mixtos de fórmula general Sm1−xAgxMnO3 con estructura perovskita en un intervalo de composición 0.1 ≤ x ≤ 0.5 por reacción convencional en estado s ´ olido. Se estudia la estructura, morfología y magnetismo de las muestras sintetizadas. Los patrones de difracción de rayos-X muestran que para x = 0.1 se tiene la presencia de una sola fase con estructura perovskita, mientras que para x ≥ 0.2 las muestras consisten de una fase perovskita ferromagnética y dos fases no magnéticas correspondientes a Ag metálica y Ag 1.8Mn8O16. El análisis de x= 0.1 por SEM revela que la morfología y tamaño de las partículas es aleatorio, resultado del método de preparación. Las muestras de Sm1−xAgxMnO3 de x entre 0.1 y 0.5 muestran, que aplicando campos de 10 Teslas, estas no alcanzan un ´ valor de saturación. El comportamiento ferromagnético de Sm1−xAgxMnO3 se ve disminuido por el aumento de la composición de Ag

Polycrystalline thin films of antimony selenide via chemical bath deposition and post deposition treatments

We report a method for obtaining thin films of polycrystalline antimony selenide via chemical bath deposition followed by heating the thin films at 573 K in selenium vapor. The thin films deposited from chemical baths containing one or more soluble complexes of antimony, and selenosulfate initially did not show X-ray diffraction (XRD) patterns corresponding to crystalline antimony selenide. Composition of the films, studied by energy dispersive X-ray analyses indicated selenium deficiency. Heating these films in presence of selenium vapor at 573 K under nitrogen (2000 mTorr) resulted in an enrichment of Se in the films. XRD peaks of such films matched Sb2Se3. Evaluation of band gap from optical spectra of such films shows absorption due to indirect transition occurring in the range of 1 – 1.2 eV. The films are photosensitive, with dark conductivity of about 2x10-8 (V cm)-1 and photoconductivity, about 106 (V cm)1 under tungsten halogen lamp illumination with intensity of 700 W m2. An estimate for the mobility life time product for the film is 4x10-9 cm2 V-1

Thin films of AgIn5(S/Se)8 prepared in a two stage process.

AgIn5(S/Se)8 thin films were prepared by sequential chemical deposition of In2S3–Ag2Se stack films and post-deposition thermal annealing in N2 atmosphere. The formations of AgIn5S8-xSex alloy was achievable through the post-deposition treatment at 350 and 400 C. X-ray diffraction and energy dispersive X-ray analyses were performed on the samples. The direct optical band gap value Eg for the films was found to be as the order of 1.75 eV at room temperature. The photo-response measurements exhibited that AgIn5(S/Se)8 thin films are photoconductive and p-type electrical conductivity of 6.6 9 10-6 (X cm)-1 and thermoelectric power of +18 lV/K

Chemical bath deposition route for the synthesis of ultra-thin CuIn(S,Se)2 based solar cells.

CuIn(S,Se)2 (CISSe) photovoltaic grade thin films are usually grown by expensive vacuum based methods or chemical routes that require highly toxic precursors. In this work, we present the synthesis of CISSe absorbers by a simple chemical bath deposition (CBD) route. In the first step, In2S3/Cu2 − xS stack was deposited as a precursor by CBD on Mo-coated soda lime glass substrates, using respectively thioacetamide and N,N′ dimethylthiourea as S source. Then the CISSe thin films were synthesized by the precursor's selenization at 450 °C. The obtained films were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The tetragonal chalcopyrite structure of CISSe was identified by XRD and Raman, confirming that the major part of S was replaced by Se. SEM images show a compact and homogeneous film and by cross-section the thickness was estimated to be around 700 nm. Solar cells prepared with these absorbers exhibit an open circuit voltage of 369 mV, a short circuit current density of 13.7 mA/cm2 , a fill factor of 45% and an efficiency of 2.3%

Effect of lanthanum on the catalytic properties of PtSn/γ-Al2O3 bimetallic catalysts prepared by successive impregnation and controlled surface reaction.

Bimetallic PtSn/γ -Al2O3–La2O3 catalysts were prepared by two comparative methods, successive impregnation (SI) and controlled surface reaction (CSR). FTIR-pyridine adsorption revealed a decrease in support acidity as a function of lanthanum content. Oxidized Pt2+ was identified by CO-FTIR chemisorption and by XPS spectra on catalysts prepared by SI. When the CSR preparation method was used, reduced Pt0 was observed and oxidized Pt2+ was not detected. As the lanthanum content increased a diminution in cyclohexane dehydrogenation and n-heptane conversion was observed. Low hydrogenolysis and high selectivity to C7-olefins were obtained in both preparations. It is proposed that lanthanum in SI catalysts stabilizes the platinum in an oxidation state, Pt2+, and diminishes the support acidity. In CSR preparations the lanthanum effect is limited to inhibit the support acidity and hence to the bifunctional reactions occurring during the n-heptane conversion

AC plasma induced modifications in Sb2S3thin films

Sb2S3 thin films, deposited by the chemical bath deposition method, were treated with N2 plasma at 3.0 Torr during several minutes. The as-prepared Sb2S3 thin films and films treated with N2 plasma have been characterized using several techniques. X-ray diffraction studies have shown that plasma treatment induced recrystallization on the as-prepared Sb2S3 thin films. The band gap values decreased from 2.37 to 1.82 eV after plasma treatment, and the electrical conductivity increased from 10 to 10 ( cm) due to the annealing effect

Iron-based Nanomaterials in the Catalysis

Available data on catalytic applications of the iron-containing nanomaterials are reviewed. Main synthesis methods of nZVI, nano-sized iron oxides and hydroxides, core-shell and alloy structures, ferrites, iron-containing supported forms, and composites are described. Supported structures include those coated and on the basis of polymers or inert inorganic materials (i.e., carbon, titania or silica). Description of catalytic processes includes the decomposition reactions (in particular photocatalytic processes), reactions of dehydrogenation, oxidation, alkylation, C–C coupling, among a series of other processes. Certain attention is paid to magnetic recovery of catalysts from reaction systems and their reuse up to several runs almost without loss of catalytic activity

Semiconductor thin films by chemical bath deposition for solar energy related applications.

In this paper we present the basic concepts underlying the chemical bath deposition technique and the recipes developed in our laboratory during the past ten years for the deposition of good-quality thin films of CdS, CdSe, ZnS, ZnSe, PbS, SnS, Bi2 S 3 , Bi2 Se3 , Sb2 S 3 , CuS, CuSe, etc. Typical growth curves, and optical and electrical properties of these films are presented. The effect of annealing the films in air on their structure and composition and on the electrical properties is notable: CdS and ZnS films become conductive through a partial conversion to oxide phase; CdSe becomes photosensitive, SnS converts to SnO2 , etc. The use of precipitates formed during deposition for screen printing and sintering, in polymer composites and as a source for vapor-phase deposition is presented. Some examples of the application of the films in solar energy related work are presented

CuInS2 thin films obtained through the annealing of chemically deposited In2S3–CuS thin films.

In this work, we report the formation of CuInS2 thin films on glass substrates by heating chemically deposited multilayers of copper sulfide (CuS) and indium sulfide (In2S3) at 300 and 350 ◦C in nitrogen atmosphere at 10 Torr. CIS thin films were prepared by varying the CuS layer thickness in the multilayers with indium sulfide. The XRD analysis showed that the crystallographic structure of the CuInS2 (JCPDS27-0159) is present on the deposited films. From the optical analysis it was estimated the band gap value for the CIS film (1.49 eV). The electrical conductivity varies from 3 × 10−8 to 3 −1 cm−1 depending on the thickness of the CuS film. CIS films showed p-type conductivity