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.

A complementary dopant system formed by hydrochloric and camphor sulfonic (CSA) acids was used in the in-situ synthesis of a polyaniline (PANi)/polyvinyl alcohol (PVA) composite. The conductivity measurements showed that the use of CSA either as single dopant or codopant caused a decrement up to 2 orders of magnitude on the overall conductivity as well as an improvement on thermal stability. The PANi/PVA composites were characterized by spectro-scopic and thermal analysis. Conducting emeraldine salt formation was confirmed by UV-VIS and FTIR spectroscopy. Microstructure analysis was performed by SEM imaging.

Se utilizó un sistema de dopaje complementario formado por ácido clorhídrico y ácido canforsulfónico (ACS) en la síntesis in-situ de un material compuesto polianilina (PANI)/alcohol polivi-nílico (APV). Las mediciones de conductividad mostraron que el uso de ACS ya sea como dopante o codopante resultó en un decremento en la conductividad total de hasta 2 órdenes de magnitud así como una mejora en la estabilidad térmica. Los compósitos PANi/APV fueron caracterizados mediante análisis térmicos y espectroscópicos. La formación de la sal esmeraldina conductora fue confirmada por espectroscopia UV-Visible e Infrarroja de Transformada de Fourier. El análisis microestructural se llevó a cabo por MEB.

Abstract A mixture of ammonium peroxydisulfate and sodium hypochlorite (NaClO) (co-oxidating system) were used to obtain polyaniline (PANi) doped with HCl and camphorsulfonic acid (CSA) (co-doping). The effect of HCl/CSA ratio added during polymerization on structure, morphology and electrical conductivity of the conducting polymer was investigated. When NaClO is used, the polymerization rate is substantially increased and the morphology changes from micrometric granular to nanometric fibrillar. CSA was used as complementary dopant but also to improve the solubility of PANi in common solvents. However, results suggest that quinone-like heterocycles containing carbonyl radicals as well as phenazine-type aromatic rings might be impeding an efficient doping in detriment of the conductivity.

Resumen El sistema de oxidación complementaria persulfato de amonio-hipoclorito de sodio (NaClO) se utilizó en la síntesis de polianilina (PANi) codopada con ácido clorhídrico y ácido canforsulfónico (ACS). Se investigó el efecto de la relación HCl/ACS presente durante la polimerización en la estructura, morfología y conductividad eléctrica del polímero conductor. Cuando se adiciona NaClO, la velocidad de polimerización aumenta notablemente y la morfología cambia de gránulos micrométricos a fibras en el rango de nanómetros. El ACS se empleó como dopante complementario y también para optimizar la solubilidad de la PANi en solventes comunes. No obstante, los resultados sugieren que los heterociclos quinonoides conteniendo radicales carbonilo así como anillos aromáticos tipo fenazina podrían obstaculizar un dopaje eficiente en detrimento de la conductividad.