| 1. |
- Broitman, E., et al.
(författare)
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Water adsorption on phosphorous-carbide thin films
- 2009
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 204:6-7, s. 1035-1039
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous phosphorous-carbide films have been considered as a new tribological coating material with unique electrical properties. However, such CPx films have not found practical use until now because they tend to oxidize/hydrolyze rapidly when in contact with air. Recently, we demonstrated that CPx thin films with a fullerene-like structure can be deposited by magnetron sputtering, whereby the structural incorporation of P atoms induces the formation of strongly bent and inter-linked graphene planes. Here, we compare the uptake of water in fullerene-like phosphorous-carbide (FL-CPx) thin films with that in amorphous phosphorous-carbide (a-CPx), and amorphous carbon (a-C) thin films. Films of each material were deposited on quartz crystal substrates by reactive DC magnetron sputtering to a thickness in the range 100-300 nm. The film microstructure was characterized by X-ray photoelectron spectroscopy, and high resolution transmission electron microscopy. A quartz crystal microbalance placed in a vacuum chamber was used to measure their water adsorption. Measurements indicate that FL-CPx films adsorbed less water than the a-CPx and a-C ones. To provide additional insight into the atomic structure of defects in the FL-CPx and a-CPx compounds, we performed first-principles calculations within the framework of density functional theory. Cohesive energy comparison reveals that the energy cost formation for dangling bonds in different configurations is considerably higher in FL-CPx than for the amorphous films. Thus, the modeling confirms the experimental results that dangling bonds are less likely in FL-CPx than in a-CPx and a-C films.
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| 2. |
- Gago, R., et al.
(författare)
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Synthesis of carbon nitride thin films by low-energy ion beam assisted evaporation : On the mechanisms for fullerene-like microstructure formation
- 2005
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 483:1-2, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nitride (CNx) thin films were grown at different substrate temperatures by low-energy (<100 eV) ion beam assistance deposition (LE-IBAD) in order to discern possible formation mechanisms of a fullerene-like (FL) microstructure. The samples are compared to those of well-structured FL-CNx films synthesized by reactive magnetron sputtering (MS). The comparison yields similar trends for both techniques, such as limitation of the nitrogen content at 20–25 at.%, dominance of sp2 hybrids, as well as thermally activated chemical desorption of CxNy species from the substrate during growth. However, CNx films produced by LE-IBAD are amorphous. The lack of FL structural features correlates with a lower degree of sp2 clustering, attributed to the promotion of nitrile groups. Therefore, low-energy ion bombardment is shown not to be a sufficient condition for the growth of FL-CNx. This result reinforces the eventual relevance of pre-formed CxNy species at the sputtering target in MS for the introduction and/or evolution of FL arrangements.
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