Abstract This work reports a study of the room-temperature synthesis of a SnO2/ZnO bilayer by magnetron sputtering. Morphological, optical, and electrical properties of the bilayer were investigated for different thicknesses of SnO2. Morphology was studied using profilometry and field emission scanning electron microscopy. The optical transmittances of the ZnO films and of the SnO2/ZnO combination were high (about 80%) in the visible, and the SnO2 film did not alter the optical properties of the ZnO, which would act as a transparent contact electrode in a perovskite solar cell.

This study reports the structural properties of zinc oxide thin films co-doped with aluminum and nitrogen (ZnO:Al-N) grown by RF magnetron sputtering from an AZO (ZnO with 2 wt% Al2O3) target under nitrogen (N2) atmosphere at room temperature (RT). Nitrogen partial pressures of 0.00, 0.10, 0.25 and 1.00 mTorr were used. The film thickness was around 270 nm. Ultraviolet-Vis-NIR transmittance (T) spectra of the films revealed T values of 80 to 85% in the 400 to 700 nm wavelength range. XRD results indicated that the films had a hexagonal wurtzite structure and were preferentially oriented in the (002) plane. Analyses by EDS indicated that the N atoms tend to be incorporated into the ZnO matrix at the expense of oxygen atoms. The ideal [N]/[Al] was obtained at a N2 partial pressure of 0.25 mTorr, producing a p-type film. For a [N]/[Al] of 1.53, the film also exhibited p-type conduction with an electrical resistivity of 31.92 Ω cm, mobility of 18.65 cm2/V s and carrier density of 1.22 x 1016 cm-3. The low carrier density is attributed to the energetically favorable formation of inactive nitrogen phases instead of acceptor-receiver-acceptor complexes, even at the ideal [N]/[Al].

Aluminum zinc oxide (AZO) thin films were synthesized on glass substrates by radio frequency (rf) magnetron sputtering from a metallic Zn-Al (5 at. %) target at room temperature. The morphological, structural, electrical and optical properties of the films were studied as a function of the sputtering pressure, which was varied from 0.1 to 6.7 Pa. X-ray diffraction (XRD) analyses revealed that the films obtained were polycrystalline, having a hexagonal wurtzite structure with a preferential orientation in the (002) plane. In addition, the crystallite size increased as a function of sputtering pressure. Owing to the re-sputtering of the Zn atoms from the growing film, the aluminum concentration presented a maximum value of 13 at. %. At pressures close to 0.16 Pa, we obtained films with values of electrical resistivity and mobility of 2.8 10-3 Ω cm and 17 cm2/Vs, respectively. Finally, our results indicate that the structure zone diagram proposed by Thornton and later modified by Kluth does not fully predict the structural/morphological behavior of the AZO films, since plasma interactions must also be taken into account. With the methodology used, transparent conductive electrodes can be deposited on substrates at low temperatures.

AbstractThe specimens of the sponges Aplysina lacunosa, Aplysina fulva, Cliona varians, Cinachyrella kuekenthali, Amphimedon viridis and Aaptos pernucleata, were collected in Mochima Bay, Venezuela,in October 2009 with the purpose of identifying families of secondary metabolites and evaluating the antibacterial properties, antifungal and brine shrimp lethal study of the ethyl acetate soluble fractions of these sponges. The chemical evaluation showed the presence of alkaloids, sterols, triterpenes, methylene ketone and tannins. The ethyl acetate soluble fractions of A. pernucleata, A. fulva and A. lacunosa sponges were the only ones that showed antibacterial activity against Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli; the soluble fraction of A. lacunosa showed the highest inhibition zones. The antifungal activity was not significant, except for A. pernucleata sponge wich showed mild activity against Candida albicans. The most prominent lethal activity in Artemia salina, were observed for C. kuekenthali, A. viridis and A. pernucleata sponges, with LC50 values of 4,10, 1,13 and < 0,01µg/mL respectively. These results allow profiling the sponges A. lacunosa, A. pernucleata and A. fulva as promising sources of antimicrobial compounds and the sponges C. kuekenthali, A. viridis and A. pernucleata as sources of antitumor compounds.

Resumen Especímenes de las esponjas Aplysina lacunosa, Aplysina fulva, Cliona varians, Cinachyrella kuekenthali, Amphimedon viridis y Aaptos pernucleata, se recolectaron en la Bahía de Mochima, Venezuela en octubre del 2009, con el propósito de identificar las familias de metabolitos secundarios y evaluar las propiedades antibacterianas, antifúngicas y letales en Artemia salina de las fracciones solubles en acetato de etilo. La evaluación química evidenció la presencia de alcaloides, esteroles, triterpenos, metilencetonas y taninos. La fracciones solubles en acetato de etilo de las esponjas A. pernucleata, A. fulva y A. lacunosa, fueron las únicas que mostraron actividad antibacteriana en contra de Staphylococcus aureus, Listeria monocytogenes y Escherichia coli, siendo A. lacunosa la que presentó los mayores halos de inhibición. La actividad antifúngica no fue significativa, a excepción de la esponja A. pernucleata, cuya fracción solublepresentó actividad leve contra Candida albicans. La actividad letal más prominente en Artemia salina, la mostraron las esponjas C. kuekenthali, A. viridis y A. pernucleata, con valores de CL50 de 4,10, 1,13 y <0,01μg/mL respectivamente. Estos resultados permiten perfilar a las esponjas A. lacunosa A. pernucleata y A. fulva como fuentes prometedora de compuestos antimicrobianos, y a las esponjas C. kuekenthali, A. viridis y A. pernucleata como fuente compuestos antitumorales.