In this work we present results and analysis concerning the processing and characterization of Gallium Nitride (GaN) thin films (TF) grown on Si (111) substrates by pulsed laser deposition technique (PLD), which were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and Raman spectroscopy (RS). The GaN films showed the hexagonal phase with a preferential orientation in the (100) direction, SEM pictures showed a cauliflower-like morphology. Room temperature PL studies showed the so called GaN-yellow band, at 2.29 eV, as well as the donor-acceptor (DA) pair luminescent transition around 3.0 eV. At 10 K, phonon replicas, separated by 69 meV, were observed. By RS, the optical mode on 710 cm-1 was observed, corresponding to the longitudinal optical phonon, A1(LO), as reported for this material.

Ammonobasic reactive sublimation (ARS) is proposed as a novel method to synthesize GaN and related oxides. Results indicate that GaN growth occurs by a nitriding process of Ga and related oxides, establishing a direct dependence on NH4OH amount added as a primary chemical reactive. The samples were grown on p-type Si (111) substrates inside a tube furnace, employing GaN powder and NH4OH. The characterizations of the samples were carried out by XRD, SEM, EDS and PL techniques, revealing the influence of NH4OH on the improvement of GaN synthesis and the enhancement of its optical and structural properties.

Zinc oxide (ZnO) films were prepared on amorphous quartz substrates by sol-gel spin-coating using Zn(CH3COO)2•2H2O precursor. Isopropanol, ethanol and 2-methoxyethanol were used as solvents. The film drying temperature was kept constant at 200 ºC and the annealing temperature was varied from 400 to 800 ºC. Highly transparent and (002)-oriented hexagonal wurtzite-type ZnO films were obtained using isopropanol solvent. The ZnO films prepared at Tanneal = 600 ºC showed the highest (002) preferential orientation, however it was not the significant feature to achieve low resistivity. The uniform and (002)-oriented ZnO films prepared at Tanneal = 400 ºC display the highest transmittance (>93% in the visible region) and the lowest resistivity (7.1 Ω•cm).

Micro and nano-fibers from polymers in solution can be easily obtained by using the so called electrospinning technique. The principle of this technique relies on applying a positive voltage to the polymer solution and a negative voltage to a collector. By increasing voltage, the surface tension will be overcome and will eject some kind of fiber deposited on the collector. The continuous fibers production will be formed like a membrane. The fibers provide a large surface area due to their small diameter, therefore, their application is considered of commercial and scientific interest. In this study, fibers from a solution made of nylon-6, polyethylene oxide and polypyrrole were obtained. Chloroform and formic acid were used as solvents for these polymers. The fibers obtained were characterized by scanning electron microscopy, FT-IR spectroscopy, X-ray diffraction and electrical conductivity. These results indicate that the diameters of the composite fibers are on the micro and nanometric range, and the conductivity thereof is that of a semiconductor material.

Las micro y nanofibras hechas a base de polímeros en solución pueden obtenerse usando una técnica llamada electrohilado. El principio de esta técnica se basa en la aplicación de una diferencia de potencial entre dos electrodos, uno conectado a la solución polimérica y otro al colector. Por el incremento de esta diferencia de potencial, la tensión superficial es superada y la fibra es formada depositándose sobre el plato colector. Las fibras continuas se producen en forma de una membrana. Estas fibras proveen una gran área superficial debido a su pequeño diámetro, esto hace que su aplicación comercial e interés científico sean considerados. En este estudio se han hecho fibras de una solución de polipirrol, óxido de polietileno y nylon-6. Se usaron como solventes cloroformo y ácido fórmico. Las fibras obtenidas son caracterizadas por microscopia electrónica de barrido, espectroscopia FTIR, difracción de rayos X y conductividad eléctrica. Los resultados indican que los diámetros del compósito están en un rango micro y nanométrico y la conductividad nos muestra el comportamiento de un material semiconductor.