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Carbon nitride films have been deposited by ECR-CVD, from Ar/CH4/N2 gas mixtures with different methane concentrations. Infrared Spectroscopy (IRS) and Elastic Recoil Detection Analysis (ERDA) have been used for films characterisation and Optical Emission Spectroscopy (OES) for plasma analysis. Argon concentration in the gas mixture controls the growth rate as well as the composition of the film. In the proposed model, argon plays a key role in the activation of methane molecules. Also, during the growth of the film, two processes may be considered: i) Film formation and ii) Etching of the growing surface. Changing the gas mixture composition affects both processes, which results in films with different composition and structure as well as different deposition rates.Se ha estudiado el efecto del argon durante el proceso de CVD asistido por un plasma ECR para la síntesis de películas de nitruro de carbono (CNxHy) a partir de mezclas gaseosas Ar/CH4/N2 con diferente contenido de metano. Las películas depositadas han sido analizadas mediante espectroscopía infrarroja (IRS) y ERDA (Elastic Recoil Detection Analysis), y el análisis del plasma ha sido realizado utilizando la técnica de espectroscopía de emisión óptica (OES). La velocidad de deposición y la composición de las películas depositadas se encuentran determinadas por la concentración de argon en la mezcla gaseosa. Se propone un modelo, según el cual el argon juega un papel fundamental como activador de las moléculas de metano. El modelo propuesto incluye dos procesos simultáneos durante el crecimiento de las capas : i) formación de la capa y ii) ataque de la superficie de crecimiento. Según la composición de la mezcla gaseosa se favorece uno u otro proceso, lo que conduce a velocidades de deposición diferentes así como a depósitos con diferente composición y estructura atómica.

In this study, we have employed infrared (IR) absorption spectroscopy, visible Raman spectroscopy, and x-ray absorption near edge structure (XANES) to quantify the hydrogen (H) content in hydrogenated amorphous carbon (a-C:H) films. a-C:H films with a hydrogen content varying from 29 to 47 at. % have been synthesized by electron cyclotron resonance chemical vapor deposition at low substrate temperatures (<120 °C) applying a wide range of bias voltage, Vb, (-300 Vb<＋100 V). With the application of high negative Vb, the a-C:H films undergo a dehydrogenation process accompanied by a sharp structural modification from polymer- to fullerenelike films. The trend in the H content derived from elastic recoil detection analysis (ERDA) is quantitatively reproduced from the intensity of the C–H bands and states in the IR and XANES spectra, respectively, as well as from the photoluminescence (PL) background drop in the Raman spectra. Using the H contents obtained by ERDA as reference data, semiquantitative expressions are inferred for the amount of bonded hydrogen as a function of the experimental spectroscopic parameters, i.e., the integrated area of the IR C–H stretching band at about 2900 cm-1, the PL background in visible Raman spectra, and the XANES intensity of the σ*-CH peak. [ABSTRACT FROM AUTHOR]

This work describes the composition and bonding structure of hydrogenated carbon nitride (a-CNx:H) films synthesized by electron cyclotron resonance chemical vapor deposition using as precursor gases argon, methane, and nitrogen. The composition of the films was derived from Rutherford backscattering and elastic recoil detection analysis and the bonding structure was examined by infrared (IR) spectroscopy and x-ray absorption near edge spectroscopy (XANES). By varying the nitrogen to methane ratio in the applied gas mixture, polymeric a-CNx:H films with N/C contents varying from 0.06 to 0.49 were obtained. Remarkably, the H content of the films (∼40 at. %) was rather unaffected by the nitrogenation process. The different bonding states as detected in the measured XANES C(1s) and N(1s) spectra have been correlated with those of a large number of reference samples. The XANES and IR spectroscopy results indicate that N atoms are efficiently incorporated into the amorphous carbon network and can be found in different bonding environments, such as pyridinelike, graphitelike, nitrilelike, and amino groups. The nitrogenation of the films results in the formation of N-H bonding environments at the cost of C-H structures. Also, the insertion of N induces a higher fraction of double bonds in the structure at the expense of the linear polymerlike chains, hence resulting in a more cross-linked solid. The formation of double bonds takes place through complex C=N structures and not by formation of graphitic aromatic rings. Also, the mechanical and tribological properties (hardness, friction, and wear) of the films have been studied as a function of the nitrogen content. Despite the major modifications in the bonding structure with nitrogen uptake, no significant changes in these properties are observed. [ABSTRACT FROM AUTHOR]

Coronaviruses of potential recombinant origin with porcine transmissible gastroenteritis virus (TGEV), referred to as a new subtype (IIb) of canine coronavirus (CCoV), were recently identified in dogs in Europe. To assess the distribution of the TGEV-like CCoV subtype, during 2001-2008 we tested fecal samples from dogs with gastroenteritis. Of 1,172 samples, 493 (42.06%) were positive for CCoV. CCoV-II was found in 218 samples, and CCoV-I and CCoV-II genotypes were found in 182. Approximately 20% of the samples with CCoV-II had the TGEV-like subtype; detection rates varied according to geographic origin. The highest and lowest rates of prevalence for CCoV-II infection were found in samples from Hungary and Greece (96.87% and 3.45%, respectively). Sequence and phylogenetic analyses showed that the CCoV-IIb strains were related to prototype TGEV-like strains in the 5' and the 3' ends of the spike protein gene. [ABSTRACT FROM AUTHOR]