Mudanças estruturais e eletronicas de filmes de carbono amorfo bombardeados por gases nobres




Amorphous carbon (a-C) compounds have attracted great attention in the past years mainly due to their interesting properties such as high hardness, low coefficient of friction, chemical inertness, e infrared transparency. However, a better understanding of the a-C microstructure is still a challenge mainly due to the ability of carbon to bond with different hybridizations (sp, sp2, e sp3). In the present work, we report a study of amorphous carbon films prepared by Ion Beam-Assisted deposition (IBAD) using different noble gases (Ne, Ar, Kr, e Xe). The deposition system consists of two Kauffman s sources, one for the sputtering of the graphite target, and another for the assisting of the film during growth. The graphite target was sputtered by a 1500 V noble gas (NG) ion beam energy. The films were prepared in the range of 0 to 800 eV NG ion beam assisting energy. For all the noble gases used, the intrinsic stress e local density (plasmon) of the films increase with increasing assisting energy , reaching high values such as 12 GPa e 29,5 eV, respectively. On the other hand, structural analysis by XPS, UPS, Raman, density , hardness, TEM, STM, EELS, conductivity , Hall measurements, among others, indicate that the material is composed of a hard, highly stressed, and locally dense graphite-like network with 90% concentration of sp2 sites. It has no report in literature of a material with these characteristics. In addition, we also observed an improvement of the electronic properties of the films (resistivity e field emission) with increasing compressive stress. Based on these results, we propose new carbon electronic devices sensitive to pressure. We suggest that the strong noble gases ion bombardment generates the stress and forces knock-on the carbon atoms beneath the surface. The increase in the internal stress reduces the distance between the sp2 clusters, increasing the local density (plasmons) e improving the electronic properties. Furthermore, the interactions between the noble gases, trapped during growth, and the carbon matrix was also explored. We observed by XANES/EXAFS the clustering of noble gases induced by the increasing matrix internal pressure


gases raros semicondutores amorfos carbono

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